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Ruthenium complexes are attracting increasing attention as second-generation metal-based anticancer agents, with NAMI-A and KP1019 as the major representatives of this class having undergone clinical trials. Our recent interest has been focused on the synthesis and characterization of new amphiphilic derivatives of nucleosides (nucleolipids). These compounds have been selected as core scaffolds linked to RuIII complexes and capable of self-assembly into stable nanostructures in aq. solutions so to transport the metal ions efficiently into the cell. Through the use of ribo- and deoxyribonucleosides as starting building blocks, a mini-library of nucleolipidic RuIII complexes decorated with diverse hydrophilic and lipophilic chains and incorporating the NAMI-A analogue AziRu has been prepared. When co-aggregated with biocompatible lipids, these RuIII-containing nucleolipids proved to be stable for months under physiological conditions. Detailed microstructural characterization, carried out by a combined approach including different physico-chemical techniques, allowed their stability, size and shape to be determined. Tested on a panel of human and non-human cells, all of the studied RuIII complexes showed potent in vitro anticancer activity, significantly higher than that of NAMI-A-like analogues, and minimal toxicity. Here we summarize the design and synthetic procedures developed to prepare these new Ru-containing candidate drugs, discussing the beneficial effects achievable through exploiting nucleolipid appendages in the delivery of metal-based drugs.

International audience; A small library of cyclic TBA analogues (named cycTBA I-IV), obtained by covalently connecting its 5'- and 3'ends with flexible linkers, has been synthesized with the aim of improving its chemical and enzymatic stability, as well as its anticoagulant properties. Two chemical procedures have been exploited to achieve the desired cyclization, based on the oxime ligation method (providing cycTBA I and II) or on Cu(I)-assisted azide-alkyne cycloaddition (CuAAC) protocols (for cycTBA III and IV), leading to analogues containing circularizing linkers with different chemical nature and length, overall spanning from 22 to 48 atoms. The resulting cyclic TBAs have been characterized using a variety of biophysical methods (UV, CD, gel electrophoresis, SE-HPLC analyses) and then tested for their serum resistance and anticoagulant activity under in vitro experiments. A fine-tuning of the length and flexibility of the linker allowed identifying a cyclic analogue, cycTBA II, with improved anticoagulant activity, associated with a dramatically stabilized G-quadruplex structure (Delta T-m = +17 degrees C) and a 6.6-fold higher enzymatic resistance in serum compared to unmodified TBA.

International audience; With the aim of developing a new approach to obtain improved aptamers, a cyclic thrombin-binding aptamer (TBA) analogue (cycTBA) has been prepared by exploiting a copper(I)-assisted azide-alkyne cycloaddition. The markedly increased serum resistance and exceptional thermal stability of the G-quadruplex versus TBA were associated with halved thrombin inhibition, which suggested that some flexibility in the TBA structure was necessary for protein recognition.

The RuIII-based prodrug AziRu efficiently binds to proteins, but the mechanism of its release is still disputed. Herein, in order to test the hypothesis of a reduction-mediated Ru release from proteins, a Raman-assisted crystallographic study on AziRu binding to a model protein (hen egg white lysozyme), in two different oxidation states, RuII and RuIII, was carried out. Our results indicate Ru reduction, but the Ru release upon reduction is dependent on the reducing agent. To better understand this process, a pH-dependent, spectroelectrochemical surface-enhanced Raman scattering (SERS) study was performed also on AziRu-functionalized Au electrodes as a surrogate and simplest model system of RuII- and RuIII-based drugs. This SERS study provided a p Ka of 6.0 ± 0.4 for aquated AziRu in the RuIII state, which falls in the watershed range of pH values separating most cancer environments from their physiological counterparts. These experiments also indicate a dramatic shift of the redox potential E0 by >600 mV of aquated AziRu toward more positive potentials upon acidification, suggesting a selective AziRu reduction in cancer lumen but not in healthy ones. It is expected that the nature of the ligands (e.g., pyridine vs imidazole, present in well-known RuIII complex NAMI-A) will modulate the p Ka and E0, without affecting the underlying reaction mechanism.

Amine-oxide surfactants have emerged as highly stable, nontoxic, and cost-effective constituents of detergent formulations, specifically as wetting agents and foam boosters. With the aim of enhancing their functional behavior, a new member of this family, N,N-dimethyl-2-propylheptan-1-amine oxide, bearing a branched alkyl tail (C 10 DAO-branched) was synthesized and purified using a simple and easily scalable strategy starting from 2-propylheptan-1-ol. 2D-nuclear magnetic resonance (NMR) and mass spectrometry confirm the obtainment of the desired product in high yield and purity. The protonation behavior of the branched surfactant is not affected by alkyl tail branching, as shown by potentiometric titrations. In contrast, surface activity and aggregation behavior of C 10 DAO-branched is dramatically different from that of the linear analog N,N-dimethyldecyl-1-amine oxide (C 10 DAO-linear), in that it occupies a higher area at the solution interface and aggregates at much higher concentration, forming larger aggregates, as detected using tensiometry and dynamic light scattering (DLS), respectively. Aggregation behavior of C 10 DAO-branched is less sensitive to pH variations. Foaming tests show that C 10 DAO-branched is a more effective foam booster than its linear analog, in both acidic and basic solutions. The experimental results indicate that the branched surfactant can be used in applications that require enhanced and pH-independent surface activity and foamability.

The great advances in the studies on metal complexes for the treatment of different cancer forms, starting from the pioneering works on platinum derivatives, have fostered an increasingly growing interest in their properties and biomedical applications. Among the various metal-containing drugs investigated thus far, ruthenium(III) complexes have emerged for their selective cytotoxic activity in vitro and promising anticancer properties in vivo, also leading to a few candidates in advanced clinical trials. Aiming at addressing the solubility, stability and cellular uptake issues of low molecular weight Ru(III)-based compounds, some research groups have proposed the development of suitable drug delivery systems (e.g., taking advantage of nanoparticles, liposomes, etc.) able to enhance their activity compared to the naked drugs. This review highlights the unique role of Ru(III) complexes in the current panorama of anticancer agents, with particular emphasis on Ru-containing nanoformulations based on the incorporation of the Ru(III) complexes into suitable nanocarriers in order to enhance their bioavailability and pharmacokinetic properties. Preclinical evaluation of these nanoaggregates is discussed with a special focus on the investigation of their mechanism of action at a molecular level, highlighting their pharmacological potential in tumour disease models and value for biomedical applications.

According to WHO, breast cancer incidence is increasing so that the search for novel chemotherapeutic options is nowadays an essential requirement to fight neoplasm subtypes. By exploring new effective metal-based chemotherapeutic strategies, many ruthenium complexes have been recently proposed as antitumour drugs, showing ability to impact on diverse cellular targets. In the framework of different molecular pathways leading to cell death in human models of breast cancer, here we demonstrate autophagy involvement behind the antiproliferative action of a ruthenium(III)-complex incorporated into a cationic nanosystem (HoThyRu/DOTAP), proved to be hitherto one of the most effective within the suite of nucleolipidic formulations we have developed for the in vivo transport of anticancer ruthenium(III)-based drugs. Indeed, evidences are implicating autophagy in both cancer development and therapy, and anticancer interventions endowed with the ability to trigger this biological response are currently considered attractive oncotherapeutic approaches. Moreover, crosstalk between apoptosis and autophagy, regulated by finely tuned metallo-chemotherapeutics, may provide novel opportunities for future improvement of cancer treatment. Following this line, our in vitro and in vivo preclinical investigations suggest that an original strategy based on suitable formulations of ruthenium(III)-complexes, inducing sustained cell death, could open new opportunities for breast cancer treatment, including the highly aggressive triple-negative subtype.

The determination of the chemical composition of different parts of wall paintings (pigments, mortars and binders) provides information about technology of preparation of an artefact. Herein, we present a multi-methodological characterisation of wall paintings from a Roman archaeological site in Cuma, focusing on differences between an indoor (domus) and outdoor fabrication (a temple, Tempio con Portico (TCP)). Both pigments, binders and mortars were studied via a combination of destructive/μ-destructive (mass spectrometry, ionic chromatography, ICP-based techniques) and non-destructive (Raman microscopy, small-angle neutron scattering (SANS) and X-ray diffraction) methodologies. Particularly, the systematic presence of dolomite only in mortars from TCP may suggest an intentional use of such limestone for the outdoor fabrication of public interest. Differences between TCP and domus are also related to the composition of the pigment binder. In particular, the detected binders (studied by LC-MS/MS and GC-MS) were proteinaceous in the case of domus (possibly egg and animal glue) and drying oils in the case of TCP. Ultimately, our multi-methodological study provides an overall picture of the material components of paintings from fabrications with different use, proposing a hypothesis on technological choices according to conservative and destination reasons.

Superparamagnetic Iron Oxide Nanoparticles (SPIONs) are performing contrast agents for Magnetic Resonance Imaging (MRI). A functionalization strategy for SPIONs based on hydrophobic interactions is a versatile approach easily extendable to several kinds of inorganic nanoparticles and suitable for obtaining stable and biocompatible systems. Here we report on the original preparation of functionalized SPIONs with an 8 nm radius exploiting the hydrophobic interaction between a phosphocholine and an inner amphiphilic. With respect to other similarly functionalized SPIONs, characterized by the typical nanoparticle clustering that leads to large aggregates, our phosphocholine-decorated SPIONs are demonstrated to be monodisperse. We report the in vitro and in vivo study that proves the effective applicability of phosphocholine-decorated SPIONs as MRI contrast agents. The versatility of this functionalization approach is highlighted by introducing on the SPION surface a ruthenium-based potential antitumoral drug, named ToThyCholRu. Even if in this case we observed the formation of SPION clusters, ascribable to the presence of the amphiphilic ruthenium complex, interesting and promising antiproliferative activity points at the ToThyCholRu-decorated SPIONs as potential theranostic agents.

Background The comprehension of the mechanism of action of antimicrobial peptides is fundamental for the design of new antibiotics. Studies performed looking at the interaction of peptides with bacterial cells offer a faithful picture of what really happens in nature. Methods In this work we focused on the interaction of the peptide Temporin L with E. coli cells, using a variety of biochemical and biophysical techniques that include: functional proteomics, docking, optical microscopy, TEM, DLS, SANS, fluorescence. Results We identified bacterial proteins specifically interacting with the peptides that belong to the divisome machinery; our data suggest that the GTPase FtsZ is the specific peptide target. Docking experiments supported the FtsZ-TL interaction; binding and enzymatic assays using recombinant FtsZ confirmed this hypothesis and revealed a competitive inhibition mechanism. Optical microscopy and TEM measurements demonstrated that, upon incubation with the peptide, bacterial cells are unable to divide forming long necklace-like cell filaments. Dynamic light scattering studies and Small Angle Neutron Scattering experiments performed on treated and untreated bacterial cells, indicated a change at the nanoscale level of the bacterial membrane. Conclusions The peptide temporin L acts by a non-membrane-lytic mechanism of action, inhibiting the divisome machinery. General significance Identification of targets of antimicrobial peptides is pivotal to the tailored design of new antimicrobials.

NU172&mdash, a 26-mer oligonucleotide able to bind exosite I of human thrombin and inhibit its activity&mdash, was the first aptamer to reach Phase II clinical studies as an anticoagulant in heart disease treatments. With the aim of favoring its functional duplex-quadruplex conformation and thus improving its enzymatic stability, as well as its thrombin inhibitory activity, herein a focused set of cyclic NU172 analogues&mdash, obtained by connecting its 5&prime, and 3&prime, extremities with flexible linkers&mdash, was synthesized. Two different chemical approaches were exploited in the cyclization procedure, one based on the oxime ligation method and the other on Cu(I)-assisted azide-alkyne cycloaddition (CuAAC), affording NU172 analogues including circularizing linkers with different length and chemical nature. The resulting cyclic NU172 derivatives were characterized using several biophysical techniques (ultraviolet (UV) and circular dichroism (CD) spectroscopies, gel electrophoresis) and then investigated for their serum resistance and anticoagulant activity in vitro. All the cyclic NU172 analogues showed higher thermal stability and nuclease resistance compared to unmodified NU172. These favorable properties were, however, associated with reduced&mdash, even though still significant&mdash, anticoagulant activity, suggesting that the conformational constraints introduced upon cyclization were somehow detrimental for protein recognition. These results provide useful information for the design of improved analogues of NU172 and related duplex-quadruplex structures.

WOS: 000497259100061, PubMed: 31629182, Two microplastic sets, polystyrene (PS) and polymethyl methacrylate (PMMA), were tested for adverse effects on early life stages of Sphaerechinus granularis sea urchins. Microparticulate PS (10, 80 and 230 mu m diameter) and PMMA (10 and 50 mu m diameter) were tested on developing S. granularis embryos from 10 min post-fertilisation (p-f) to the pluteus larval stage (72 h p-f), at concentrations ranging from 0.1 to 5 mg L-1. Both PS and PMMA exposures resulted in significant concentration-related increase of developmental defects and of microplastic uptake in plutei. Moreover, embryo exposures to PS and PMMA (5 and 50 mg L-1) from 10 min to 5 h p-f resulted in a significant increase of cytogenetic abnormalities, expressed as significantly increased mitotic aberrations, while mitotoxicity (as % embryos lacking active mitoses) was observed in embryos exposed to PS, though not to PMMA. When S. granularis sperm suspensions were exposed for 10 min to PS or to PMMA (0.1-5 mg L-1), a significant decrease of fertilisation success was observed following sperm exposure to 0.1 mg L-1 PS, though not to higher PS concentrations nor to PMMA. Sperm pretreatment, however, resulted in significant offspring damage, as excess developmental defects in plutei, both following sperm exposure to PS and PMMA, thus suggesting transmissible damage from sperm pronuclei to the offspring. the overall results point to relevant developmental, cytogenetic and genotoxic effects of PS and PMMA microplastics to S. granularis early life stages, warranting further investigations of other microplastics and other target biota., Croatian Science Foundation [IP-2018-01-5351]; Environment and Climate Change Canada, This work has been supported by the Croatian Science Foundation under project IP-2018-01-5351. Financial support from Environment and Climate Change Canada is also gratefully acknowledged. Declarations of conflict: none.

Diffusion plays a central part in many unit operations. The Maxwell-Stefan model is the dominant model for both gaseous and liquid diffusion. However, it was developed from the kinetic theory of gases, raising the question of whether it can be extended to non-ideal liquid systems. The dynamic fluctuation model is an alternative model based on the Cussler theory and predicts a smaller thermodynamic influence relative to the linear influence of the Maxwell-Stefan model due to dynamic concentration fluctuations. Since the dynamic fluctuation model, which uses the scaling factor α, had improved performance relative to the Maxwell-Stefan model for a wide range of binary systems, it is postulated that this improved performance should also be observed for a ternary system. In this work, the dynamic molecular fluctuation model was extended to a highly non-ideal ternary system, using the same scaling factor α, through matrix manipulation. Using self-diffusion data measured by NMR, mutual diffusion predictions of the developed model and the Maxwell-Stefan model were compared to experimental mutual diffusion data of the partially miscible system ethanol/toluene/n-decane. It is demonstrated that the dynamic fluctuation model gives improved predictions relative to the Maxwell-Stefan approach, consistent with previous observations on binary systems, showing that the reduced thermodynamic influence of the dynamic fluctuation model is an improvement. In addition, we show that the use of local mole fractions, to account for molecular association, in both the dynamic fluctuation and Maxwell-Stefan models, results in improved diffusion predictions for the ternary system. The results confirm that the dynamic fluctuation model improves predictions of mutual diffusion in liquid mixtures, suggesting a non-linear correction to the thermodynamic correction factor. The results also suggest that that the key assumptions in the Maxwell-Stefan model and its derivation, rooted in the kinetic theory of gases, are not entirely accurate for highly non-ideal liquid systems. The optimum α for the ternary system studied here is approximately 0.45, similarly to the optimum α of 0.40 to 0.80 for a range of binary systems previously studied, suggesting that the use of the α scaling factor, which is grounded in scaling laws theory, is of general validity.

AS1411 is a nucleolin-binding aptamer which attracted great interest as active targeting ligand for the selective delivery of therapeutic agents to tumour cells. In this work we selected three AS1411 derivatives 5′-conjugated with lipophilic tails and studied their properties in view of their application in liposomial formulations and/or lipid coated-nanoparticles for targeted therapies. The conformational behaviour of these AS1411 analogs has been investigated in comparison with the unmodified aptamer by CD, UV, PAGE, SEC-HPLC, DLS and thioflavin T (ThT) fluorescence assays to get insight in their secondary structure and aggregation properties. This study has been performed in pseudo-physiological buffers mimicking the extra- and intracellular environments, and at different concentrations in the μM range, paying special attention to the effects of the lipophilic tail on the overall aptamer conformation. The 5′-lipidated AS1411 derivatives proved to fold into stable, parallel unimolecular G-quadruplex structures, forming large aggregates, mainly micelles, at conc. >10 μM. Preliminary bioscreenings on selected cancer cells showed that these derivatives are less cytotoxic than AS1411, but maintain a similar biological behaviour. This study demonstrated that lipophilic tails dramatically favour the formation of AS1411 aggregates, however not impairing the formation and thermal stability of its peculiar G4 motifs.

The ion-specific effect on the solubility of macromolecules in water, rationalized through the Hofmeister series, can be used as an effective method to obtain polymer particles with desired microstructural properties thanks to the so-called salting out effect. By choosing the proper salt and optimizing the polymer and the salt concentration, it is possible to tailor the particle structural features like the radius and the degree of compactness and to speed up the aggregation process until complete conversion from free chains to aggregates. Here we rationalize the segregation of poly-ethylene-vinyl alcohol (EVOH) chains in the presence of sodium chloride (NaCl). The effect of polymer and salt concentrations on the kinetics and the thermodynamics of the aggregation process is considered. In particular, we show how such parameters influence the microstructural properties of the particles through a combination of light and neutron scattering techniques as well as microscopy. We found that by increasing sodium chloride concentration it is possible to speed up the aggregation process, obtaining a complete conversion from free chains to aggregates at shorter times, whereas increasing poly-ethylene-vinyl alcohol concentration from 0.70% w/w to 1.30% w/w determines an increase of the microgel size of a two-times factor. Moreover, NaCl concentration directly affects both the packing degree of the polymer chains within the aggregate and the morphology of the polymer particle, leading to a more compact structure at higher NaCl concentrations. Understanding how it is possible to tune both aggregation kinetics and EVOH particle microstructure is fundamental in order to give a general picture which could be broadened to the class of vinyl alcohol-based polymers.

In the search for more efficient anticancer treatments, Ru(III) complexes have attracted much interest among metal-based candidate drugs, showing marked antitumor and antimetastatic activity associated with lower systemic toxicity. Remarkable examples are the Ru(III) complexes NAMI-A and KP1019, which have reached advanced clinical evaluation. In order to improve the in vivo stability of Ru(III)-based drugs, as well as their cellular uptake and effectiveness, a new approach has been proposed by our research group, based on the incorporation of the active, NAMI-A-like Ru(III) complex into highly functionalized nucleolipidic structures, i.e., hybrid molecules containing a nucleoside or nucleotide central core derivatized with a lipid chain, ensuring both efficient protection against extracellular degradation and high cellular internalization of the metal. Aiming at expanding the chemical diversity of available amphiphilic Ru(III) complexes, we here selected a trifunctional α-amino acid to replace the nucleosidic core of previously prepared nucleolipid-based Ru(III) complexes. The amino acidic scaffold, linked to the Ru(III) complex, is decorated with both hydrophilic and lipophilic moieties, conferring high propensity to form stable aggregates in water, which is required to obtain a suitable nanocarrier for the drug delivery. Following this approach, a novel compound, indicated here as compound I, was successfully prepared and characterized, then studied in coformulation with the biocompatible cationic lipid 1,2-dioleyl-3-trimethylammoniumpropane chloride (DOTAP) by dynamic light scattering (DLS), small angle neutron scattering (SANS), and UV–vis analysis. Evaluated in vitro on a panel of human and nonhuman cell lines, it showed good antiproliferative activity on cancer cells, with IC50 values in the μM range, and no relevant cytotoxicity on the healthy cells used as control.

The interaction of the anticancer Ru(iii) complex AziRu - in comparison with its analogue NAMI-A, currently in advanced clinical trials as an antimetastatic agent - with DNA model systems, both single stranded and duplex oligonucleotides, was investigated using a combined approach, including absorption UV-vis spectroscopy, circular dichroism (CD) and electrospray mass spectrometry (ESI-MS) techniques. UV-vis absorption spectra of the Ru complexes were recorded at different times in a pseudo-physiological solution, to monitor the ligand exchange processes in the absence and in the presence of the examined oligonucleotides. CD experiments provided information on the overall conformational changes of the DNA model systems induced by these metal complexes. UV- and CD-monitored thermal denaturation studies were performed to analyse the effects of AziRu and NAMI-A on the stability of the duplex structures. ESI-MS experiments, carried out on the oligonucleotide/metal complex mixtures under investigation, allowed us to detect the formation of stable adducts between the guanine-containing oligomers and the ruthenium complexes. These data unambiguously demonstrate that both AziRu and NAMI-A can interact with the DNA model systems. Although very similar in their structures, the two metal compounds manifest a markedly different reactivity with the examined sequences, respectively, with either a naked Ru(3+) ion or a Ru(Im)(3+) (Im = imidazole) fragment being incorporated into the oligonucleotide structure via stable linkages.

International audience; Progress in understanding and treatment of thrombotic diseases requires new effective methods for the easy, rapid, and reversible control of coagulation processes. In this framework, the use of aptamers, and particularly of the thrombin binding aptamer (TBA), has aroused strong interest, due to its enormous therapeutic potential, associated with a large number of possible applications in biotechnological and bioanalytical fields. Here, we describe a new TBA analogue (named tris-mTBA), carrying three different pendant groups: a dansyl residue at the 3 '- and a beta-cyclodextrin moiety at the 5 '-end-providing a host-guest system which exhibits a marked fluorescence enhancement upon TBA G-quadruplex folding-and a biotin tag, allowing the attachment of the aptamer onto biocompatible streptavidin-coated silica nanoparticles (NPs) of 50 nm hydrodynamic diameter (Sicastar). The use of nanoparticles for the in vivo delivery of TBA, expected to induce per se increased nuclease resistance and improved pharmacokinetic properties of this oligonucleotide, offers as an additional advantage the possibility to exploit multivalency effects, due to the presence of multiple copies of TBA on a single scaffold. In addition, the selected fluorescent system allows monitoring both the presence of TBA on the functionalized NPs and its correct folding upon immobilization, also conferring enhanced enzymatic resistance and bioactivity. The anticoagulant activity of the new tris-mTBA, free or conjugated to Sicastar NPs, was evaluated by dynamic light scattering experiments. Highly effective and reversible inhibition of thrombin activity toward fibrinogen was found for the free tris-mTBA and especially for the tris-mTBA-conjugated NPs, demonstrating great potential for the biomedical control of blood clotting.

Several threonine (Thr)- and alanine (Ala)-rich antifreeze glycoproteins (AFGPs) and polysaccharides act in nature as ice recrystallization inhibitors. Among them, the Thr-decorated capsular polysaccharide (CPS) from the cold-adapted Colwellia psychrerythraea 34H bacterium was recently investigated for its cryoprotectant activity. A semisynthetic mimic thereof was here prepared from microbial sourced chondroitin through a four-step strategy, involving a partial protection of the chondroitin polysaccharide as a key step for gaining an unprecedented quantitative amidation of its glucuronic acid units. In-depth NMR and computational analysis suggested a fairly linear conformation for the semisynthetic polysaccharide, for which the antifreeze activity by a quantitative ice recrystallization inhibition assay was measured. We compared the structure-activity relationships for the Thr-derivatized chondroitin and the natural Thr-decorated CPS from C. psychrerythraea. Several threonine (Thr)- and alanine (Ala)-rich antifreeze glycoproteins (AFGPs) and polysaccharides act in nature as ice recrystallization inhibitors. Among them, the Thr-decorated capsular polysaccharide (CPS) from the cold-adapted Colwellia psychrerythraea 34H bacterium was recently investigated for its cryoprotectant activity. A semisynthetic mimic thereof was here prepared from microbial sourced chondroitin through a four-step strategy, involving a partial protection of the chondroitin polysaccharide as a key step for gaining an unprecedented quantitative amidation of its glucuronic acid units. In-depth NMR and computational analysis suggested a fairly linear conformation for the semisynthetic polysaccharide, for which the antifreeze activity by a quantitative ice recrystallization inhibition assay was measured. We compared the structure-activity relationships for the Thr-derivatized chondroitin and the natural Thr-decorated CPS from C. psychrerythraea.

Looking for new metal-based anticancer treatments, in recent years many ruthenium complexes have been proposed as effective and safe potential drugs. In this context we have recently developed a novel approach for the in vivo delivery of Ru(III) complexes, preparing stable ruthenium-based nucleolipidic nanoaggregates endowed with significant antiproliferative activity. Herein we describe the cellular response to our ruthenium-containing formulations in selected models of human breast cancer. By in vitro bioscreens in the context of preclinical studies, we have focused on their ability to inhibit breast cancer cell proliferation by the activation of the intrinsic apoptotic pathway, possibly via mitochondrial perturbations involving Bcl-2 family members and predisposing to programmed cell death. In addition, the most efficient ruthenium-containing cationic nanoaggregates we have hitherto developed are able to elicit both extrinsic and intrinsic apoptosis, as well as autophagy. To limit chemoresistance and counteract uncontrolled proliferation, multiple cell death pathways activation by metal-based chemotherapeutics is a challenging, yet very promising strategy for targeted therapy development in aggressive cancer diseases, such as triple-negative breast cancer with limited treatment options. These outcomes provide valuable, original knowledge on ruthenium-based candidate drugs and new insights for future optimized cancer treatment protocols.

The spontaneous oxidative polymerization of 0.01-1% w/w 5,6-dihydroxyindole (DHI) in chicken egg white (CEW) in the absence of added solvents leads to a black, water-soluble, and processable artificial biomelanin (ABM) with robust and 1 order of magnitude stronger broadband light absorption compared to natural and synthetic eumelanin suspensions. Small angle neutron scattering (SANS) and transmission electron microscopy (TEM) analysis indicated the presence in the ABM matrix of isolated eumelanin nanoparticles (=100 nm) differing in shape from pure DHI melanin nanoparticles (SANS evidence). Electron paramagnetic resonance (EPR) spectra showed a slightly asymmetric signal (g similar to 2.0035) similar to that of solid DHI melanin but with a smaller amplitude (Delta B), suggesting hindered spin delocalization in biomatrix. Enhanced light absorption, altered nanoparticle morphology and decreased free radical delocalization in ABM would reflect CEW-induced inhibition of eumelanin aggregation during polymerization accompanied in part by covalent binding of growing polymer to the proteins (SDS-PAGE evidence). The technological potential of eumelanin nanosizing by biomimetic synthesis within a CEW biomatrix is demonstrated by the preparation of an ABM-based black flexible film with characteristics comparable to those of commercially available polymers typically used in electronics and biomedical applications.

The synthesis, formulation and a complete physico-chemical characterization, by dynamic light scattering and small angle neutron scattering techniques, of new liposomal aggregates obtained by co-assembling an amphiphilic molecule containing a platinum complex, Peg1500 -Lys(Pt-aminoEtGly)-Lys(C18)2, (abbreviated as (C18)2-PKAG-Pt), with a second amphiphilic monomer, (C18H37)2NCO(CH2)2CO(AdOO)5-Oct ((C18)2 L5-Oct), containing the octreotide bioactive peptide, is reported. Liposomes of (C18)2-PKAG-Pt present a radius of 48 nm, whereas the mixed aggregates (C18)2-PKAG-Pt/(C18)2L5-Oct at 90/10 M ratio give larger liposomes with a radius of 84 nm. In both cases, the bilayer thickness is ~5.3 nm. Encapsulation of doxorubicin in mixed liposomes is also obtained by using the pH gradient method. The obtained liposomes could represent a new target selective cargo system for delivery of cisplatin based drugs and/or doxorubicin on cells overexpressing the sstr2 and sstr5 somatostatin receptors.

© 2016 Elsevier Ltd. A new model for prediction of mutual diffusion coefficients is proposed over the whole composition range for binary liquid systems of one self-associating component and one non-polar component. The model is based on the Darken equation with the knowledge of intra-diffusion coefficients at infinite dilution of both species and viscosity data for the system, and takes into account the cluster diffusion approach with a scaling power on the thermodynamic correction factor. The model was validated to show good concurrence with the experimental mutual diffusion data. Following the analysis that the mutual diffusion coefficients at infinite dilution can be identified with the molecular intra-diffusion coefficient of the species (i.e., the intra-diffusion coefficient at infinite dilution in the absence of self-association), the proposed equation was extended to binary liquid systems without significant association. The accuracy of prediction for systems of cross associating species is expected to be limited. The model relies on the knowledge of the viscosity of the mixture over the whole composition range and may be used as a valid alternative to models based on measuring intra-diffusion coefficients as a function of composition. Indeed, such data are not always available or are more difficult to obtain whereas viscosity measurements can be readily available and more easily measured.

Hydrophobins are fungal proteins whose functions are mainly based on their capability to self-assemble into amphiphilic films at hydrophobic-hydrophilic interfaces (HHI). It is widely accepted that class I hydrophobins form amyloid-like structures, named rodlets, which are hundreds of nanometers long, packed into ordered lateral assemblies and do not exhibit an overall helical structure. We studied the self-assembly of the Class I hydrophobin Vmh2 from Pleurotus ostreatus in aqueous solutions by dynamic light scattering (DLS), thioflavin T (ThT), fluorescence assay, circular dichroism (CD), cryogenic trasmission electron microscopy (cryo-TEM), and TEM. Vmh2 does not form fibrillar aggregates at HHI. It exhibits spherical and fibrillar assemblies whose ratio depends on the protein concentration when freshly solubilized at pH ≥ 7. Moreover, it spontaneously self-assembles into isolated, micrometer long, and twisted amyloid fibrils, observed for the first time in fungal hydrophobins. This process is promoted by acidic pH, temperature, and Ca(2+) ions. A model of self-assembly into amyloid-like structures has been proposed.

Liposomes are complex aggregates, often including polyethylene glycol (PEG) to expand their life span in vivo, although their full biocompatibility is still questioned. With the aim to suitably replace PEG within liposomal formulations, here we propose a new liposomes formulation, which includes an amphiphilic molecule of natural origin: the lipooligosaccharide (LOS) from the Gram-negative bacterium Rhizobium rubi. LOS architecture is bifunctional: the lipid moiety at one terminus promotes its insertion into the liposome, the other terminus is hydrophilic and in this case presents an oligosaccharide motif similar to the human Lewis B antigen. Liposomes were prepared by co-formulating de-O-acylated LOS (de-LOS) with the lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and the anticancer nucleolipid-based Ru(III) complex, ToThyRu. In-depth microstructural characterization shows that de-LOS containing liposomes are stable aggregates. In vitro preliminary bioscreens have disclosed their negligible toxic profile and a good uptake in MCF-7 and HaCaT cells. The results validate the use of lipooligosaccharides in formulating liposomes and pave the way to their use in drug delivery applications.

SuperParamagnetic Iron Oxide Nanoparticles (SPIONs) represent a suitable system for several applications especially in nanomedicine. Great efforts have been made to design stable and biocompatible functionalized SPIONs suitable for diagnostics and drug delivery. In particular, zwitterionic-surfactant functionalized SPIONs, obtained through a coating strategy based on hydrophobic interaction, are promising systems for biomedical applications. The size of functionalized SPIONs has emerged as a crucial parameter determining their fate in living organisms. However, not all the proposed functionalization strategies lead to monodispersed systems and SPION clustering often occurs. In this study, we report a systematic investigation on different surfactant-functionalized SPIONs in order to explore the possibility of tuning the particle size by choosing an appropriate amphiphilic molecule. By combining Small-Angle Neutron Scattering (SANS) and Dynamic Light Scattering (DLS) analysis, we have provided a detailed description of the functionalized SPION structure. Furthermore, we have also related the surfactant aggregation properties, i.e. the Critical Micelle Concentration (CMC), to their efficiency in coating the SPION surface. A lack in the formation of a compact shell leads to a clusters formation. On this basis, the present study contributes to furnishing decisive information to define synthetic strategies able to tune functionalized-SPION design.

A new organometallic ruthenium complex, named AziRu, along with three amphiphilic nucleoside-based ruthenium complexes, ToThyRu, HoThyRu and DoHuRu, incorporating AziRu in their skeleton, have been synthesized, stabilized in POPC phospholipid formulations and studied for their antineoplastic activity. Self-aggregation behavior of these complexes was investigated, showing that the three synthesized AziRu derivatives able to form liposomes and, under specific conditions, elongated micelles. The formulations prepared in POPC proved to be stable for months and showed high in vitro antiproliferative activity. The here described results open new scenarios in the design of innovative transition metal-based supramolecular systems for anticancer drugs vectorization.

Ionophores are an important class of synthetic molecules which mimic natural ion channels or carriers. Here we report the aggregation behavior in pseudo-physiological environment of three Cyclic Phosphate-Linked Oligosaccharides (CyPLOS) derivatives, synthetic ion transporters based on cyclic, phosphate-linked disaccharide skeleton differing for the nature of the tails (tetraethylene–TEG glycol and/or n-undecyl chains) attached to the C-2 and C-3 of the constitutive monosaccharides. Their aggregation behavior has been studied by a combined use of dynamic light scattering (DLS), electron paramagnetic resonance spectroscopy (EPR) and Small Angle Neutron Scattering (SANS). DLS measurements were performed to reveal the formation and size distribution of the CyPLOS aggregates. EPR measurements, by using 5-doxyl stearic acid (5-DSA) as spin-probe, showed that the aggregates are mainly due to the formation of double layers and allowed to analyze the local fluidity. Finally, SANS measurements allowed estimating the layer thickness of the double layers. Our results indicate that the three CyPLOS analogs show self-aggregation properties that depend on the different nature of the inserted tails.

The mutual diffusion coefficients, Dij, of the ternary system sodium cholate (NaC, component 1) + sodium deoxycholate (NadC, component 2) + water have been determined at five average compositions (c1, c2) keeping c1 constant and varying c2. The possibility to obtain expressions for the four diffusion coefficients in term of the micellization parameters and of the diffusivity of the species in solution is discussed. Data have been qualitatively interpreted. Results for the main term diffusion coefficients have been used in the much more difficult analysis of the cross term diffusion coefficients.

This chapter presents a summary of papers published in the period June 2008–May 2009 focusing on the use and implementation of NMR techniques to elucidate the microstructure and dynamics of self-assembled systems.

We have experimentally investigated multicomponent diffusion in a protein-polymer-salt-water quaternary system. Specifically, we have measured the nine multicomponent diffusion coefficients, D(ij), for the lysozyme-poly(ethylene glycol)-NaCl-water system at pH 4.5 and 25 degrees C using precision Rayleigh interferometry. Lysozyme is a model protein for protein-crystallization and enzymology studies. We find that the protein diffusion coefficient, D(11), decreases as polymer concentration increases at a given salt concentration. This behavior can be quantitatively related to the corresponding increase in fluid viscosity only at low polymer concentration. However, at high polymer concentration (250 g/L), protein diffusion is enhanced compared to the corresponding viscosity prediction. We also find that a protein concentration gradient induces salt diffusion from high to low protein concentration. This effect increases in the presence of poly(ethylene glycol). Finally, we have evaluated systematic errors associated with measurements of protein diffusion coefficients by dynamic light scattering. This work overall helps characterize protein diffusion in crowded environments and may provide guidance for further theoretical developments in the field of protein crystallization and protein diffusion in such crowded systems, such as the cytoplasm of living cells.

Natural polyamines (putrescine, spermidine, and spermine) self-assemble in a simulated physiological environment (50 mm sodium phosphate buffer, pH 7.2), generating in vitro nuclear aggregates of polyamines (ivNAPs). These supramolecular compounds are similar in structure and molecular mass to naturally occurring cellular nuclear aggregates of polyamines, and they share the ability of NAPs to interact with and protect the genomic DNA against nuclease degradation. Three main ivNAP compounds were separated by gel permeation chromatography. Their elution was carried out with 50 mm sodium phosphate buffer supplemented with 150 mm NaCl. Freezing and thawing of selected chromatographic fractions obtained by GPC runs in which the mobile phase was sodium phosphate buffer not supplemented with NaCl yielded three different microcrystallites, specifically corresponding to the ivNAPs, all of which were able to bind DNA. In this study, we demonstrated that in vitro self-assembly of polyamines and phosphates is a spontaneous, reproducible and inexpensive event, and provided the indications for the production of the ivNAPs as a new tool for manipulating the genomic DNA machinery.

A theoretical spinodal curve for the system water + chloroform + acetic acid at 25 °C is derived using a lattice model for ternary amphiphilic solutions: rod-like molecules covering the bonds of the honeycomb lattice with three-body interactions between the molecular ends associated to the same lattice site. The molecular model is equivalent to the standard Ising model on the same lattice; its mean-field solution is the most appropriate for reproducing, by local fitting, the experimental data for the binodal composition. The derived spinodal curve is in very good agreement with the spinodal composition determined also in the present work from the measured diffusion coefficients recently reported for the same system.

Self-complementary synthetic peptides, composed by 8 and 16 residues, were analyzed by CD, NMR and small angle neutron scattering (SANS) techniques in order to investigate the relevance of charge and hydrophobic interactions in determining their self-assembling properties. All the sequences are potentially able to form fibrils and membranes as they share, with the prototype EAK16, a strictly alternating arrangement of polar and nonpolar residues. We find that 16-mer peptides show higher self-assembling propensities than the 8-mer analogs and that the aggregation processes are favored by salts and neutral pH. Peptide hydrophobic character appears as the most relevant factor in determining self-assembling. Solution conformational analysis, diffusion and SANS measurements all together show that the sequences with a higher self-assemble propensity are distributed, in mild conditions, between light and heavy forms. For some of the systems, the light form is mostly constituted by monomers in a random conformation, while the heavy one is constituted by beta-aggregates. In our study we also verified that sequences designed to adopt extended conformation, when dissolved in alcohol-water mixtures, can easily fold in helix structures. In that media, the prototype of the series appears distributed between helical monomers and beta-aggregates. It is worth noticing that the structural conversion from helical monomer to beta-aggregates, mimics beta-amyloid peptide aggregation mechanisms.

The chemical synthesis by solid-phase methods of a novel amphiphilic peptide, peptide-conjugate amphiphile (PCA), containing in the same molecule three different functions: (i) the N,N-bis[2-[bis(carboxy-ethyl)amino]ethyl]-L-glutamic acid (DTPAGlu) chelating agent, (ii) the CCK8 bioactive peptide, and (iii) a hydrophobic moiety containing four alkyl chains with 18 carbon atoms each, is reported. In water solution at pH 7.4, PCA self-assembles in very stable micelles at very low concentration [critical micellar concentration (cmc) values of 5 x 10(-7) mol kg(-1)] as confirmed by fluorescence spectroscopy. The structural characterization, obtained with small-angle neutron scattering (SANS) measurements, indicates that the aggregates are substantially represented by ellipsoidal micelles with an aggregation number of 39 +/- 2 and the two micellar axes of about 52 and 26 A.

The structural and relaxometric characterization of a novel class of supramolecular aggregates, as potential tumor-specific contrast agents in magnetic resonance imaging (MRI), is reported. The aggregates are based on a new monomer with an upsilon shape (MonY) that contains, in the same molecule, all three fundamental tasks that are required: 1) a hydrophobic moiety that allows the formation of supramolecular aggregates; 2) the bioactive CCK8 peptide for target recognition; and 3) a chelating agent able to give stable gadolinium complexes. As indicated by dynamic light scattering and small-angle neutron scattering (SANS) measurements, MonY and its gadolinium complex MonY(Gd) aggregate in aqueous solution to give ellipsoidal micelles with a ratio between the micellar axes of approximately 1.7 and an aggregation number N(agg) of approximately 30. There are no differences in the aggregation behavior of MonY and MonY(Gd), which indicates that the presence of metal ions, and therefore the reduction of the net charge, does not influence the aggregation behavior. When MonY or MonY(Gd) are blended with dioleoyl phosphatidylcholine (DOPC), the aggregation behavior is dictated by the tendency of DOPC to give liposomes. Only when the amount of MonY or MonY(Gd) is higher than 20 % is the coexistence of liposomes and micelles observed. The thickness d of the bilayer is estimated by SANS to be approximately 35-40 A, whereas cryogenic transmission electron microscopy images show that the diameter of the liposomes ranges from approximately 50 to 150 nm. Self-assembling micelles of MonY(Gd) present high relaxivity values (r(1p)=15.03 mM(-1) s(-1)) for each gadolinium complex in the aggregate. Liposomes containing MonY(Gd) inserted in the DOPC bilayer at a molar ratio of 20:80 present slightly lower relaxivity values (r(1p)=12.7 mM(-1) s(-1)), independently of their internal or external position in the liposome.

The diffusion coefficients, D ij , for the ternary system water + chloroform + acetic acid are reported at five compositions. This system presents a large solubility gap due to the almost complete insolubility between water and chloroform. The analyzed compositions have a fixed mole ratio of water and chloroform and a decreasing amount of acetic acid when approaching the binodal curve. The difficulty of interpreting the D ij is stressed, and the use of different choices of which component is the solvent and a different reference frame for the diffusive transport is suggested to extract all the possible information from the diffusion coefficients.

The interactions between proteins/peptides and lipid bilayers are fundamental in a variety of key biological processes, and among these, the membrane fusion process operated by viral glycoproteins is one of the most important, being a fundamental step of the infectious event. In the case of the feline immunodeficiency virus (FIV), a small region of the membrane proximal external region (MPER) of the glycoprotein gp36 has been demonstrated to be necessary for the infection to occur, being able to destabilize the membranes to be fused. In this study, we report a physicochemical characterization of the interaction process between an eight-residue peptide, named C8, modeled on that gp36 region and some biological membrane models (liposomes) by using calorimetric and spectroscopic measurements. CD studies have shown that the peptide conformation changes upon binding to the liposomes. Interestingly, the peptide folds from a disordered structure (in the absence of liposomes) to a more ordered structure with a low but significant helix content. Isothermal titration calorimetry (ITC) and differential scanning calorimetry (DSC) results show that C8 binds with high affinity the lipid bilayers and induces a significant perturbation/reorganization of the lipid membrane structure. The type and the extent of such membrane reorganization depend on the membrane composition. These findings provide interesting insights into the role of this short peptide fragment in the mechanism of virus-cell fusion, demonstrating its ability to induce lipid segregation in biomembranes.

Nanostructured hydrogels composed by biocompatible molecules are formulated and characterized. They are based on a polymer network formed by hydrophobically modified chitosans (HMCHIT or CnCHIT) in which vesicles of monoolein (MO) and oleic acid or sodium oleate (NaO), depending on pH , are embedded. The best conditions for gel formation, in terms of pH , length of the hydrophobic moieties of chitosan, and weight proportion among the three components were estimated by visual inspection of a large number of samples. Among all possible combinations, the system C12CHIT–MO–NaO in the weight proportion (1:1:1) is optimal for the formation of a well-structured gel-like system, which is also confirmed by rheological experiments. Electron paramagnetic resonance (EPR) measurements unambiguously show the presence of lipid bilayers in this mixture, indicating that MO–NaO vesicles are stabilized by C12CHIT even at acid pH . A wide small angle neutron scattering investigation performed on several ternary systems of general formula CnCHIT–MO–NaO shows that the length of the hydrophobic tail Cn is a crucial parameter in stabilizing the polymer network in which lipid vesicles are embedded. Structural parameters for the vesicles are determined by using a multilamellar model that admits the possibility of displacement of the center of each shell. The number of shells tends to be reduced by increasing the polymer content. The thickness and the distance between consecutive lamellae are not influenced by either the polymer or MO–NaO concentration. The hydrogel presented in this work, being fully biocompatible and nanostructured, is well-suited for possible application in drug delivery.

A novel nanocomposite system composed of hydrophobically modified ethoxylated urethane (so-called HEUR) polymer, which is a telechelic polymer, and coated magnetite (Fe3O4) nanoparticles (MNp) is investigated. Two different kinds of nanoparticle coatings, are used: a hydrophobic coating composed of oleic acid and oleylamine and a hydrophilic coating having the cationic surfactant C(18)TAB as an additional layer to the hydrophobic nanoparticles. The structure of the nanocomposites as hydrogels with either MNp separately is analyzed using small angle neutron scattering (SANS). Furthermore, the dried state is studied in complementary SANS experiments. The magnetic response of the dried state is characterized by magnometry observing a superparamagnetic behavior.

We use accurate thermodynamic derivatives extracted from high-precision measurements of the four volume-fixed diffusion coefficients in ternary solutions of lysozyme chloride in aqueous NaCl, NH4Cl, and KCl at pH 4.5 and 25 degrees C to (a) assess the relative contributions of the common-ion and nonideality effects to the protein chemical potential as a function of salt concentration, (b) compare the behavior of the protein chemical potential for the three salts, which we found to be consistent with the Hofmeister series, and (c) discuss our thermodynamic data in relation to the dependence of the protein solubility on salt concentration. The four diffusion coefficients are reported at 0.6 mM lysozyme chloride and 0.25, 0.5, 0.9, 1.2, and 1.5 M KCl and extend into the protein-supersaturated region. The chemical potential cross-derivatives are extracted from diffusion data using the Onsager reciprocal relation and the equality of molal cross-derivatives of solute chemical potentials. They are compared to those calculated previously from diffusion data for lysozyme in aqueous NaCl and NH4Cl. We estimate the effective charge on the diffusing lysozyme cation at the experimental concentrations. Our diffusion measurements on the three salts allowed us to analyze and interpret the four diffusion coefficients for charged proteins in the presence of 1:1 electrolytes. Our results may provide guidance to the understanding of protein crystallization.

Poly(asparagine) (pAsn) at 0.1wt % in the presence of dodecyltrimethylammonium bromide (DTAB) and pentaoxyethylene octyl ether (C(8)E(5)) at 1:1 molar ratio leads to the formation of mixed DTAB/C(8)E(5) micelle-like aggregates onto the polypeptide as a total surfactant critical association concentration (cac) is reached, as revealed by surface tension measurements and NMR chemical shifts. Two-dimensional nuclear Overhauser enhancement spectroscopy (NOESY) capable of revealing spatial relationships among proximal protons has been performed on the pAsn-DTAB-C(8)E(5)-water system to study structural details of the surfactant-polypeptide aggregates. NOESY cross-peaks at sample temperature of 298.15 K indicate that the polypeptide interacts with the DTAB/C(8)E(5) micelle-like aggregates. The NOE intermolecular effects also show direct interactions between surfactant and polypeptide in the pAsn-DTAB-water system, whereas no interaction has been revealed in the pAsn-C(8)E(5)-water system. Furthermore, the experimental evidence suggest that the DTAB-polypeptide complex is mainly driven by the polar attraction between the two molecules.

The structural organization of matter in poly(vinyl alcohol) (PVA) hydrogels obtained by repeatedly freezing and thawing dilute solutions of PVA in D2O is investigated by use of small-angle neutron scattering measurements (SANS). This study is the first systematic and quantitative investigation in the medium range of length scales on PVA hydrogels obtained by freezing and thawing techniques. The studied gels have a complex hierarchical structure, extending over a wide range of length scales. The structural organization on the micron length scale originates from the presence of two separated phases constituted by polymer-rich and polymer-poor regions. The network structure may be interpreted in terms of the connectivity of the regions occupied by the polymer-rich phase, which extend over the macroscopic dimensions of the sample. The organization on the medium length scale is provided by the presence of small crystallites, fringed micelle-like, within the polymer-rich phase. In these regions, the crystals are highly connected by swollen amorphous tie chains. The presence of these tie chains ensures the connectivity of the macroscopic network. The structural organization on the short length scale is essentially provided by the relative arrangement of chains within the crystallites and in the swollen amorphous zones. The PVA hydrogel structure has been modeled as a collection of polydisperse and homogeneous spherical crystallites, interacting via hard-spheres potential. SANS experiments permitted us to obtain values of the crystallite size of about 33 Angstrom, of the volume fraction of polymer-rich phase of the order of 1% and a value of the average crystallite-crystallite correlation distances of the order of a few tens of nanometers, independent of the imposed number of freeze/thaw cycles (n), for n > 1. The present analysis also indicates that the structure of the gel obtained imposing a single freeze/thaw cycle is somehow intermediate between the structure of the homogeneous starting solution and the structure of the already well-formed sample obtained by imposing two consecutive cycles.

Small angle neutron scattering (SANS) has been used to study the interaction of sodium decyl sulfate (C100S) and sodium decanesulfonate (C10S) with poly(vinylpyrrolidone) (PVP). The measurements were performed on aqueous solutions of C100S and C10S in the presence and absence of PVP. In all ternary systems the polymer concentration was kept constant at I wt%, and the surfactant molal concentration ranged from 0.002 to 0.150 mol kg(-1). The analysis of the collected SANS profiles confirms the absence of any appreciable interaction between PVP and C10S in contrast with what observed for the PVP-C100S-D2O system. In this latter system, in fact, a clear interaction peak in the scattering pattern appears well below the cmc of the surfactant, which suggests a complex formation between PVP and C100S. The preferential interaction of poly(vinylpyrrolidone) toward sodium decyl sulfate with respect to sodium decanesulfonate reflects the difference in the chemical structure of the two surfactants that produces meaningful differences in the values of their cmc and aggregation number, as shown by the results here presented.

Measurements of osmotic coefficients, mutual diffusion coefficients, and conductivity were performed on the binary system sodium n-octyl sulfonate (C8SO3Na)-water at 25degreesC both below and above the micellar composition range. The osmotic coefficient data were obtained through vapor-pressure osmometry, while the Taylor dispersion method was used to measure diffusion coefficients. The mass equilibrium model was applied to this self-aggregating system, taking into account the deviation of the activity coefficients from the Debye-Huckel limiting law by using the Guggenheim corrective terms for mixed electrolyte solutions. The expressions derived from the model fit the experimental osmotic and diffusion coefficient data well, when the same values of aggregation number, fraction of condensed counterions, and equilibrium constant are used. Osmotic coefficients were also used to determine the thermodynamic factor required to compute the solute mobility from diffusion data. Conductivity data were used to test two theoretical models, namely, the Onsager-Fuoss and the Mean Spherical Approximation theories. Both models have been found to yield unsatisfactory fits to our experimental data and some arbitrary terms had to be applied to the theoretical expressions to obtain good agreement between experiment and theory.

The transport properties of NaCl in poly(ethylene glycol)-water (PEG-water) mixtures are presented, with special regard to the dielectric and hydrodynamic effects. We report experimental data of mutual diffusion, viscosity, and conductivity for the aqueous ternary system containing PEG with an average molecular weight of 2000 a.m.u. (PEG2000, component 1) and sodium chloride (NaCl, component 2). Both PEG2000 and NaCl are used extensively as protein-crystallizing agents. The four diffusion coefficients ( D11, D12, D21, and D22) that are required to describe the diffusive properties of a ternary system correctly were determined by the precise Gouy interferometric method. We also report measurements of the dielectric constant for several aqueous binary systems containing PEG with three different molecular weights (200, 400, and 2000 a.m.u.), which significantly decreases the dielectric constant of aqueous solutions. The experimental values of the four diffusion coefficients are discussed in terms of obstruction, excluded volume, and dielectric effects. The dependence of the PEG main-term diffusion coefficient, D11, on the salt concentration is quantitatively described by the corresponding change of viscosity. The cross-term diffusion coefficients, D12 and D21, are described in terms of excluded volume effects and PEG-salt nonpreferential interactions. The dependence of the salt main term diffusion coefficient, D22, on PEG concentration is essentially due to obstruction effects. Moreover, a remarkable agreement between D22 and the salt equivalent conductivity has been determined. This correlation suggests that, even though the dielectric constant significantly changes in the presence of PEG, the electrostatic ion-ion interactions (the summation of the extent of ion-pairing and electrophoretic contributions) are not significantly modified by the polymer. This analysis of the diffusive and conductivity properties of electrolytes in the presence of PEG have allowed us to clarify important aspects of the electrostatic properties of aqueous PEG-salt systems and supplies valuable information for salt properties in “mixed solvents”. A useful classification of mixed solvents is proposed, distinguishing between “viscous” and “dielectric” mixed solvents.

We investigate the precision of Rayleigh interferometry in evaluating the nine mutual diffusion coefficients Dij defining a four-component system by investigating the system lysozyme−tetra(ethylene glycol)−NaCl−H2O. We believe our results to be the most successful experimental determination of diffusion coefficients in quaternary systems. This choice of system is motivated by its relevance to protein crystal growth. The comparison of the Dij coefficients of the quaternary system and the Dij coefficients from the corresponding ternary and binary systems enables us to extract some information about the hydrodynamics and thermodynamics in solutions where protein crystals grow.

The ternary system water–pentaethyleneglycol monooctyl ether (C8E5)–octyltrimethyl ammonium bromide (C8TAB) has been studied at 25 °C. Accurate c.m.c. values have been determined through spectrofluorimetric measurements, by using DL-tryptophan as a molecular probe. The surfactant intradiffusion coefficients have been measured through the PGSE-NMR technique. Experimental data show the formation of mixed micelles. The compositions of the aqueous and micellar pseudo-phase have been computed over the whole micellar composition range; they indicate that C8E5 has a larger tendency to form aggregates than C8TAB. The aggregation number and the Gibbs energy of mixed micelle formation are calculated and interpreted in terms of interactions among the surfactants in the micellar aggregates. The experimental results have been compared with those predicted by the regular solution model finding reasonable agreement.