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Zwitterionic sulfobetaine surfactants are used in pharmaceutical or biomedical applications for the solubilization and delivery of hydrophobic molecules in aqueous medium or in biological environments. In a screening on the biocidal activity of synthetic surfactants on microbial cells, remarkable results have emerged with sulfobetaine amphiphiles. The interaction between eight zwitterionic sulfobetaine amphiphiles and Saccharomyces cerevisiae model cells was therefore analyzed. S. cerevisiae yeast cells were chosen, as they are a widely used unicellular eukaryotic model organism in cell biology. Conductivity measurements were used to investigate the interaction between surfactant solution and cells. Viable counts measurements were performed, and the mortality data correlated with the conductivity profiles very well, in terms of the inflection points (IPs) observed in the curves and in terms of supramolecular properties of the aggregates. A Fourier transform infrared (FTIR)-based bioassay was then performed to determine the metabolomic stress-response of the cells subjected to the action of zwitterionic surfactants. The surfactants showed nodal concentration (IPs) with all the techniques in their activities, corresponding to the critical micellar concentrations of the amphiphiles. This is due to the pseudocationic behavior of sulfobetaine micelles, because of their charge distribution and charge densities. This behavior permits the interaction of the micellar aggregates with the cells, and the structure of the surfactant monomers has impact on the mortality and the metabolomic response data observed. On the other hand, the concentrations that are necessary to provoke a biocidal activity do not promote these amphiphiles as potential antimicrobial agents. In fact, they are much higher than the ones of cationic surfactants.

Novel diastereomeric anionic amphiphiles based on the rigid cyclobutane β-amino acid scaffold have been synthesized and deeply investigated with the aim of generating new functional supramolecular architectures on the basis of the rational design of original amphiphilic molecules and the control of their self-assembly. The main interest has been focused on the effect that cis/trans stereochemistry exerts on their molecular organization and recognition. In diluted solutions, the relative stereochemistry mainly influences the headgroup solvation and anionic-charge stabilization, i.e., better stabilized in the cis diastereoisomer due to intramolecular hydrogen-bonding and/or charge-dipole interactions. This provokes differences in their physicochemical behavior (pKa, cmc, conductivity) as well as in the structural parameters of the spherical micelles formed. Although both diastereoisomers form fibers that evolve with time from the spherical micelles, they display markedly different morphology and kinetics of formation. In the lyotropic liquid crystal domain, the greatest differences are observed at the highest concentrations and can be ascribed to different hydrogen-bonding and molecular packing imposed by the stereochemical constraints. Remarkably, the spherical micelles of the two anionic surfactants show dramatically diverse enantioselection ability for bilirubin enantiomers. In addition, both the surfactants form heteroaggregates with bilirubin at submicellar concentrations but with a different expression of supramolecular chirality. This points out that the unlike relative configuration of the two surfactants influences their chiral recognition ability as well as the fashion in which chirality is expressed at the supramolecular level by controlling the molecular organization in both micellar aggregates and surfactant/bilirubin heteroaggregates. All these differential features can be appropriate and useful for the design and development of new soft materials with predictable and tunable properties and reveal the cyclobutane motif as a valuable scaffold for the preparation of new amphiphiles.

Nanoporous electrified surfaces create a unique nonfaradaic electrochemical behavior that is sensitively influenced by pore size, morphology, ionic strength, and electric field modulation. Here, we report the contributions of ion concentration and applied ac frequency to the electrode impedance through an electrical double layer overlap and ion transport along the nanopores. Nanoporous Pt with uniform pore size and geometry (L2-ePt) responded more sensitively to conductivity changes in aqueous solutions than Pt black with poor uniformity despite similar real surface areas and enabled the previously difficult quantitative conductometry measurements at high electrolyte concentrations. The nanopores of L2-ePt were more effective in reducing the electrode impedance and exhibited superior linear responses to not only flat Pt but also Pt black, leading to successful conductometric detection in ion chromatography without ion suppressors and at high ionic strengths.

The complex formation of Ni(ClO4)2 and Mg(ClO4)2 with 3-hydroxyflavone (HL, flavonol) in acetonitrile was studied using conductometric and spectroscopic methods. It was found that interaction of nickel cation with HL leads to formation of the doubly charged [Ni(HL)](2+) complex, whereas in solutions of magnesium perchlorate the complex with anion [MgClO4(HL)](+) is formed. Using the extended Lee-Wheaton equation, the limiting equivalent conductivities of [Ni(HL)](2+) and [MgClO4(HL)](+) and thermodynamic constants of their formation were obtained at 288, 298, 308, 318, and 328 K. Calculated Stoke's radii indicate weak solvation of the formed complexes and low temperature stability of their solvation shells. On the basis of the quantum chemical calculations and noncovalent interactions analysis, it is found that in the solvated [Ni(HL)](2+) and [MgClO4(HL)](+) complexes interaction of the Ni(2+) and Mg(2+) cations with flavonol occurs via the carbonyl group of HL. Complexation with Ni(2+) does not change the internal structure of HL greatly: in the [Ni(HL)](2+) complex, flavonol shows an intramolecular H-bond between 3-hydroxyl and carbonyl groups. When a complex with [MgClO4](+) is formed, the OH group turns out of the plane of the chromone moiety that leads to rupture of an intramolecular H-bond in the ligand molecule. Moreover, in the [MgClO4(HL)](+) complex, perchlorate anion possesses a strong ability to interact with HL, forming an intracomplex H-bond between hydrogen of the 3-hydroxyl group and oxygen of ClO4(-). Its strength is more pronounced than in the intramolecular one in both [Ni(HL)](2+) and uncomplexed 3-hydroxyflavone.

Conductometric monitoring of protein-protein and protein-sterol interactions is here proved feasible by coupling quartz crystal microbalance with dissipation monitoring (QCM_D) to nucleic acid programmable protein arrays (NAPPA). The conductance curves measured in NAPPA microarrays printed on quartz surface allowed the identification of binding events between the immobilized proteins and the query. NAPPA allows the immobilization on the quartz surface of a wide range of proteins and can be easily adapted to generate innumerous types of biosensors. Indeed multiple proteins on the same quartz crystal have been tested and envisaged proving the possibility of analyzing the same array for several distinct interactions. Two examples of NAPPA-based conductometer applications with clinical relevance are presented herein, the interaction between the transcription factors Jun and ATF2 and the interaction between Cytochrome P540scc and cholesterol.

In the present work, the effect of a surface modification protocol along with the electrode size has been investigated for developing an efficient, label-free electrochemical biosensing method for diagnosis of traumatic brain injury (TBI) biomarkers. A microdisk electrode array (MDEA) and a macroelectrode with a comb structure (MECS) were modified with an anti-GFAP (GFAP = glial fibrillary acidic protein) antibody using two protocols for optimum and label-free detection of GFAP, a promising acute-phase TBI biomarker. For the MDEA, an array of six microdisks with a 100 μm diameter and, for the MECS, a 3.2 mm × 5.5 mm electrode 5 μm wide with 10 μm spaced comb fingers were modified using an optimized protocol for dithiobis(succinimidyl propionate) (DSP) self-assembled monolayer formation. Anti-GFAP was covalently bound, and the remaining free DSP groups were blocked using ethanolamine (Ea). Sensors were exposed to solutions with different GFAP concentrations, and a label-free electrochemical impedance spectroscopy (EIS) technique was used to determine the concentration. EIS results confirmed that both types of Ea/anti-GFAP/DSP/Au electrodes modified with an optimized DSP-based protocol can accurately detect GFAP in the range of 1 pg mL(-1) to 100 ng mL(-1) with a detection limit of 1 pg mL(-1). However, the cross-use of the MDEA protocol on the MECS and vice versa resulted in very low sensitivity or poor signal resolution, underscoring the importance of proper matching of the electrode size and type and the surface modification protocol.

Colloidal dispersions of silver bromide (AgBr) in aqueous surfactant medium have been prepared using a surfactant-assisted synthesis approach with hexadecyltrimethylammonium bromide (CTAB). The surfactant acts both as source of bromide ion as well as the stabilizing agent. Upon progressive addition of silver nitrate to aqueous CTAB solution, stable AgBr dispersions were obtained. Formation of surfactant cation (CTA(+)) stabilized AgBr was confirmed by way of XRD, FTIR and NMR studies. Thermal behavior of the isolated nanoparticles was investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), where the occurrence of phase transition in the surfactant-stabilized nanoparticles was observed. Kinetics of the particle growth was investigated by dynamic light scattering measurements, which predicted the formation of surfactant bilayered structures associated with the nanoparticles of AgBr. Band gap of the nanoparticles was determined by suitably analyzing the UV-visible spectral data, which concluded that the particles behaved like insulators. Morphology of the particles, studied by TEM measurements, was found to be spherical. Finally, enthalpy of formation of surfactant-stabilized AgBr, determined calorimetrically, was found to be dependent on the concentration of the precursors.

A systematic study of osmotic coefficient, conductivity, volumetric and acoustic properties of solutions of ionic liquid 1-hexyl-3-methylimidazolium chloride ([C(6)mim][Cl]) in various molecular solvents has been made at different temperatures in order to study of ionic association and solvation behavior of [C(6)mim][Cl] in different solutions. Precise measurements on electrical conductances of solutions of [C(6)mim][Cl] in water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and acetonitrile at 293.15, 298.15, and 303.15 K are reported and analyzed with Barthel's low-concentration chemical model (lcCM) to obtain the limiting molar conductivities and association constants of this ionic liquid in the investigated solvents. Strong ion pairing was found for the ionic liquid in 2-propanol, 1-butanol, and 1-propanol, whereas ion association in acetonitrile, methanol and ethanol is rather weak and in water the ionic liquid is fully dissociated. In the second part of this work, the apparent molar volumes and isentropic compressibilities of [C(6)mim][Cl] in water, methanol, ethanol, acetonitrile, 1-propanol, 2-propanol, and 1-butanol are obtained at the 288.15-313.15 K temperature range at 5 K intervals at atmospheric pressure from the precise measurements of density and sound velocity. The infinite dilution apparent molar volume and isentropic compressibility values of the free ions and ion pairs of [C(6)mim][Cl] in the investigated solvents as well as the excess molar volume of the investigated solutions are determined and their variations with temperature and type of solvents are also studied. Finally, the experimental measurements of osmotic coefficient at 318.15 K for binary solutions of [C(6)mim][Cl] in water, methanol, ethanol, 2-propanol, and acetonitrile are taken using the vapor pressure osmometry (VPO) method and from which the values of the solvent activity, vapor pressure, activity coefficients, and Gibbs free energies are calculated. The results are interpreted in terms of ion association, ion-dipole interactions, and structural factors of the ionic liquid and investigated organic solvents. The ionic liquid is solvated to a different extent by the molecular solvents, and ionic association is affected significantly by ionic solvation.

In this contribution, we report studies on the nature of binding of a potent antituberculosis drug, Rifampicin (RF) with a model drug delivery system, sodium dodecyl sulfate (SDS) micelle. Temperature dependent dynamic light scattering (DLS), conductometry, and circular dichroism (CD) spectroscopy have been employed to study the binding interaction of the drug with the micelle. The absorption spectrum of the drug RF in the visible region has been employed to study Förster resonance energy transfer (FRET) from another fluorescent drug Hoechst 33258 (H33258), bound to the micelle. Picosecond-resolved FRET studies at room temperature confirm the simultaneous binding of the two drugs to the micelle and the distance between the donor-acceptor pair is found to be 34 Å. The temperature dependent FRET study also confirms that the location and efficiency of drug binding to the micelle changes significantly at the elevated temperature. The energy transfer efficiency of the donor H33258, as measured from time-resolved studies, decreases significantly from 76% at 20 °C to 60% at 55 °C. This reveals detachment of some amount of the drug molecules from the micelles and increased donor-acceptor distance at elevated temperatures. The estimated donor-acceptor distance increases from a value of 33 Å at 20 °C to 37 Å at 55 °C. The picosecond resolved FRET studies on a synthesized DNA bound H33258 in RF solution have been performed to explore the interaction between the two. Our studies are expected to find relevance in the exploration of a potential vehicle for the vital drug rifampicin.

A new macrocyclic bolaamphiphile with thiocytosine fragments in the molecule (B1) has been synthesized and advanced as perspective platform for the design of soft supramolecular systems. Strong concentration-dependent structural behavior is observed in the water-DMF (20% vol) solution of B1 as revealed by methods of tensiometry, conductometry, dynamic light scattering, and atomic force microscopy. Two breakpoints are observed in the surface tension isotherms. The first one, around 0.002 M, is identified as a critical micelle concentration (cmc), whereas the second critical concentration of 0.01 M is a turning point between the two models of the association involved. Large aggregates of ca. 200 nm are mostly formed beyond the cmc, whereas small micelle-like aggregates exist above 0.01 M. The growth of aggregates between these critical points occurs, resulting in a gel-like behavior. An unusual decrease in the solution pH with concentration takes place, which is assumed to originate from the steric hindrance around the B1 head groups. Because of controllable structural behavior, B1 is assumed to be a candidate for the development of biomimetic catalysts, nanocontainers, drug and gene carriers, etc.

Interaction of gelatin (G) with room temperature ionic liquids (ILs), 3-methyl-1-octylimidazolium chloride [C(8)mim][Cl] and 1-butyl-3-methylimidazolium octylsulfate [C(4)mim][C(8)OSO(3)], have been investigated through tensiometry, conductivity, steady-state fluorescence, turbidity, and dynamic light scattering (DLS). We have observed that the nature of interactions in G-[C(8)mim][Cl] system are remarkably different as compared to G-[C(4)mim][C(8)OSO(3)] system. At low concentrations, much below the critical micelle concentration (cmc) of IL, the IL monomers are adsorbed at the native G at the interface forming G-IL (monomer) complex, whereas both the monomers and lower IL aggregates are interacted with G in bulk leading to G-IL (aggregate) complex. The increased hydrophobic character of the G-IL complexes is evidenced from pyrene fluorescence. Turbidity measurements showed interestingly distinguished coacervation characteristics in the investigated systems. In case of G-[C(4)mim][C(8)OSO(3)] system, the coacervates dissolve in the free micellar solution whereas G-[C(8)mim][Cl] coacervates remain stable up to very high concentration. DLS provided useful information about the changes in size of gelatin and the nature of interactions between gelatin and ILs. Thermodynamic parameters of micellization with and without gelatin have been derived and compared.

In emergency cases anticoagulant action of heparin needs to be stopped instantaneously, which is usually achieved by intravenous administration of protamine sulfate (PS). However, PS shows many adverse effects. The objective of the present work was to find out if chitosan (Ch) and a cationically modified chitosan, N-(2-hydroxypropyl)-3-trimethylammonium chitosan chloride (HTCC), may be applied for heparin reversal. For chitosan the efficiency of unfractionated heparin (UFH) binding decreases with increasing pH while for cationically modified chitosan heparin binding is efficient even for high pH values. Complexation of UFH and low-molecular-weight heparin (LMWH) by cationically modified chitosan in the aqueous solution at pH = 7.4 was studied. Complexes of the modified chitosan with UFH are smaller and of lower dispersity than those with PS. Cationically modified chitosan was found to bind both UFH and LMWH. The complex formation capability of cationically modified chitosan is comparable to that of PS.

The compaction of calf thymus DNA (CT-DNA) by cationic liposomes constituted by a 1:1 mixture of a cationic lipid, 1,2-distearoyl-3-(trimethylammonio)propane chloride (DSTAP), and a zwitterionic lipid, 1,2-dioleoyl-sn-glycero-3-phosphatidylethanolamine (DOPE, null net charge at pH = 7.4), has been evaluated in aqueous buffered solution at 298.15 K by means of conductometry, electrophoretic mobility, cryo-TEM, and fluorescence spectroscopy techniques. The results reveal that DSTAP/DOPE liposomes are mostly spherical and unilamelar, with a mean diameter of around 77 +/- 20 nm and a positively charged surface with a charge density of sigmazeta = (21 +/- 1) x 10(-3) C m(-2). When CT-DNA is present, the genosomes DSTAP/DOPE/CT-DNA, formed by means of a surface electrostatic interaction, are generally smaller than the liposomes. Furthermore, they show a tendency to fuse forming cluster-type structures when approaching isoneutrality, which has been determined by the electrochemical methods at around (L/D)phi = 5.6. The analysis of the decrease on the fluorescence emission of the fluorophore ethidium bromide, EtBr, initially intercalated between DNA base pairs, as long as the genosomes are formed has permitted us to confirm the electrostatic character of the DNA-liposome interaction.

Neuropathy target esterase (NTE) is a membrane protein found in human neurons and other cells, including lymphocytes. Binding of certain organophosphorus (OP) compounds to NTE is believed to cause OP-induced delayed neuropathy (OPIDN), a type of paralysis for which there is no effective treatment. Mutations in NTE have also been linked with serious neurological diseases, such as motor neuron disease. This paper describes development of the first nanostructured biosensor interface containing a catalytically active fragment of NTE known as NEST. The biosensor was fabricated using the layer-by-layer assembly approach, by immobilizing a layer of NEST on top of multilayers consisting of a polyelectrolyte (poly-L-lysine) and an enzyme (tyrosinase). The biosensor has a response time on the order of seconds and gives a concentration-dependent decrease in sensor output in response to a known NEST (and NTE) inhibitor. Potential applications of the biosensor include screening OP compounds for NTE inhibition and investigating the enzymology of wild-type and mutant forms of NTE. Although the development of a NEST biosensor was the primary purpose of this study, we found that the approach developed for NEST could also be extended to measure the activity of other esterases involved in neural processes, such as acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). On the basis of measured sensitivities, phenyl valerate was the preferred substrate for NEST and BChE, whereas phenyl acetate was better for AChE.

The electrochemistry of a series of dendrimers was examined at the interface between two immiscible electrolyte solutions (ITIES), enabling study of non-redox-active dendrimers. Different generations of poly(propylenimine) (DAB-AM-n) and poly(amidoamine) (PAMAM) dendrimers were studied. In their protonated states, the dendrimers were transferred across the ITIES, with the electrochemical behavior observed depending on the dendrimer family, the generation number, and the experimental pH. The electrochemistry of the lower generations studied was characterized by well-defined peaks for both dendrimer families and with small peak-peak separations in the case of the PAMAM family. The voltammetry of the higher generations was more complex, showing distorted voltammograms and instability of the interface. The charges of the transferring dendrimers were calculated by convolution of the voltammetric data and were similar to the theoretical charges for DAB-AM-n. For PAMAM, only the lowest generation exhibited reversible behavior, with higher generations having irreversible behavior. Using cyclic voltammetry, low micromolar concentrations of the dendrimers were detected. The results show that electrochemistry at the ITIES can be a useful method for characterization of ionizable dendrimers and that voltammetry can be a simple method for detection of low concentrations of these multicharged species.

The formation of spontaneous mixed prevesicles and vesicles consisting of a cationic double-chain surfactant, didecyldimethylammonium bromide (di-C(10)DMAB), and a cationic single-chain alkyltrimethylammonium bromide with 10 and/or 14 carbon atoms (decyltrimethylammonium bromide, C(10)TAB, and/or tetradecyltrimethylammonium bromide, C(14)TAB) has been investigated by means of a series of (i) highly precise experimental techniques, such as conductometry, transmission electronic microscopies (TEM and cryo-TEM), laser Doppler electrophoresis (LDE), and steady-state fluorescence spectroscopy and (ii) theoretical models, such as the DLVO theory and two of its main further modifications, Inoues's and Sogami's models. Two new potentials, based on the combination of DLVO or Inoue potentials with that of Sogami, have been proposed and checked. This theoretical analysis has been carried out not only for the aggregates studied in this work but also for other di-C(m)DMAB + C(n)TAB (m = 10, 12 and n = 10, 12, 14) systems previously reported by us. In respect to the experimental study, special emphasis has been devoted to the prevesicle domain. We have confirmed the existence of two critical aggregation concentrations in the very diluted concentration domain, where the conductivity plot shows a zigzag pattern: the so-called mixed critical aggregate concentration, CAC* and the mixed critical vesicle concentration, CVC*. Contrarily, only CVC* is detected. The pre-CAC* nanoaggregates, with a variety of sizes and shapes, do not show a clear aggregation pattern, but even at such low concentrations a small number of nanoaggregates with a clear and ordered aggregation pattern has been visualized. In the postvesicle domain, the aggregates (vesicles) are unilamellar and spherical with a medium polidispersity and a net averaged surface density charge of around 14 x 10(-3) (pure vesicles) and 24 x 10(-3) C m(-2) (mixed vesicles). The hydrophobicities of the lipidic bilayer and the surface of the vesicles resemble those of media with dielectric constants of around 30 and 75, respectively. Finally, theoretical predictions confirm the stability of the pure and mixed vesicles studied in this work and in other works previously reported.

Standard solution Gibbs energies, DeltasG degrees, of the resorcarene-based receptor 5,11,17,23-ethylthiomethylated calix[4]resorcarene, (characterized by 1H NMR and X-ray diffraction studies) in its monomeric state (established through partition experiments) in various solvents are for the first time reported in the area of resorcarene chemistry. Transfer Gibbs energies of from hexane (reference solvent) to other medium are calculated. Agreement between DeltatG degrees (referred to the pure solvents) and standard partition Gibbs energies, DeltapG degrees (solvent mutually saturated) is found. Cation-ligand interactions were investigated through 1H NMR (CD3CN and CD3OD) and conductometric titrations in acetonitrile and methanol. 1H NMR data revealed the sites of interaction of with the metal cation. The composition of the metal-ion complexes (Ag+ and Pb2+ in acetonitrile and Ag+ and Cu2+ in methanol) was established through conductometric titrations. Thus, complexes of 1:1 stoichiometry were formed between and Ag+ and Pb2+ in acetonitrile and Cu2+ in methanol. However, in moving from acetonitrile to methanol, the composition of the silver complex was altered. Thus, two metal cations are hosted by a unit of the ligand. As far as Cu2+ and in acetonitrile is concerned, conductance data suggest that metalates are formed in which up to four units of Cu2+ are taken up per unit of resorcarene. The contrasting behavior of with Cu2+ in acetonitrile relative to methanol is discussed. As far as mercury (II) is concerned, the unusual jump in conductance observed in the titration of Hg2+ with in acetonitrile and methanol after the formation of a multicharged complex (undefined composition) is attributed to the presence of highly charged smaller units (higher mobility) resulting from the departure of pendant arms from the resorcarene backbone. Isolation of these species followed by X-ray diffraction studies corroborated this statement. The thermodynamic characterization of metal-ion complexes of Ag+ and Pb2+ in acetonitrile and Cu2+ and Ag+ in methanol is reported. Final conclusions are given.

The interaction of calix[3]thieno[1]pyrrole, 1, and halide and dihydrogen phosphate anions in a variety of solvents (acetonitrile, propylene carbonate, N,N-dimethylformamide, and dimethyl sulfoxide) has been investigated through 1H NMR, conductance measurements, and titration calorimetry. 1H NMR measurements reveal the sites of interaction of the ligand with the anions in CD3CN while the composition of the complex was determined through conductance measurements. A quantitative assessment of anion-ligand interactions is provided. Thus the thermodynamics of complexation of 1 with halide and dihydrogen phosphate anions in dipolar aprotic media at 298.15 K is reported. These data are interpreted in terms of the thermodynamics of transfer of reactants and product from a reference solvent (acetonitrile) to other solvents. The crucial role played by the solvent on the ability of the ligand to interact with anions and on the composition of the complex is demonstrated.

Reaction of N-methylbenzothiazole-2-thione (C8H7NS2 or NMBZT) with diiodine produced the charge-transfer (ct) complex [(NMBZT).I2] (1). NMBZT reacts with diiodine in the presence of FeCl3 in a molar ratio of 3:6:1 and forms the ionic complex [[(NMBZT)2I+].[FeCl4]-] (2) together with [[(NMBZT)2I+].[I7]-] (2a) iodonium salt. The reaction of benzimidazole-2-thione (C7H6N2S or MBZIM) with diiodine on the other hand results in the formation of the ct [[(MBZIM)2I]+[I3]-].[(MBZIM).I2] (3) compound. The compounds have been characterized by elemental analyses, DTA-TG, FT-Raman, FT-IR, UV-vis, and 1H NMR spectroscopies, and X-ray crystal structure determinations. Compound 1, C8H7I2NS2, is orthorhombic with a space group Pna2(1) and a = 12.5147(13) angstroms, b = 22.536(3) angstroms, c = 4.2994(5) angstroms, and Z = 4. Compound 2, C16H14Cl4FeIN2S4, is monoclinic, space group C2/c, a = 35.781(2) angstroms, b = 7.4761(5) angstroms, c = 18.4677(12) angstroms, beta = 107.219(1) degrees, and Z = 8. Compound 3, C21H18I6N6S3, monoclinic, space group P2(1)/n, a = 14.0652(11) angstroms, b = 22.536(3) angstroms, c = 4.2994(5) angstroms, beta = 99.635(7) degrees, and Z = 4, consists of two component moieties cocrystallized, one neutral which contains the benzimidazole-2-thione (MBIZM) ligand bonded with an iodine atom through sulfur, forming a compound with a "spoke" structure [(MBZIM)I2] 3a, while the other is the ionic complex [[(MBZII)2I+].[I3]-] (3b). The X-ray crystal structure of 1 shows a bond between the thione-sulfur atom and one of the iodine atoms in an essentially planar arrangement. In the cation of 2, an iodine is coordinated by two thione-sulfur atoms in a linear arrangement but the molecule is not planar. For the first time in the solid state a spoke-ionic mixed complex has been characterized in 3. One component of the structure is a molecular diiodine adduct, i.e., [(MBZIM)I2] (3a), with a linear coordination geometry in a decidedly planar arrangement, and the other component is an ionic adduct [[(MBZIM)2I]+.[I3]-] (3b) with the cation having an arrangement similar to that found for 1. Theoretical calculations using density functional (DFT) and ab initio Hartree-Fock theory have been carried out for 1 and 3a,b. The results are consistent with the experimental data. Conclusions on the behavior of a thioamide, when used as an antithyroid drug, have also been made.

Interaction of sodium dodecyl sulfate (SDS) with a globular protein, trypsin, has been physicochemically studied in aqueous medium in detail using tensiometric, conductometric, calorimetric, fluorimetric, viscometric, and circular dichroism techniques. The results indicate that SDS-trypsin aggregates start to form at a surfactant concentration higher than the critical micelle concentration of pure SDS micelle. In contrast, the counterion binding decreases in the presence of trypsin. The free energies and enthalpies of micellization, interfacial adsorption, and entropy of micellization associated with the interaction have also been calculated. The values show that the interaction phenomenon is entropy controlled and endothermic in nature. The increase in viscosity is observed for the system of SDS-trypsin cluster above the critical micelle concentration of SDS micelle only. The aggregation number and interface polarity decrease compared to the values of micelles without protein. Circular dichroism spectra show the high alpha-helical content and unfolded structure of trypsin in the presence of SDS due to strong electrostatic repulsion leading to a probable "necklace and bead" model in the case of biopolymer-surfactant complexes.