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Background A new G-quadruplex structure located in the B-cell CLL/lymphoma 2 (Bcl-2) P1 promoter and its physiological function related to Bcl-2 transcription have been studied to find a potential anticancer therapeutic target. Methods Absorption, polyacrylamide gel electrophoresis, fluorescence, circular dichroism, and nuclear magnetic resonance spectra have been employed to determine G-quadruplex structure and the interaction between G-quadruplex and phenanthrolin-dicarboxylate. Real time polymerase chain reaction and luciferase assay were done to assess the physiological function of the G-quadruplex structure. Results The UV-melting and polyacrylamide gel electrophoresis studies show that the p32 DNA sequence forms an intramolecular G-quadruplex structure. Circular dichroism and nuclear magnetic resonance spectra indicate that the G-quadruplex is a hybrid-type structure with four G-tetrads. Fluorescence spectra show that a phenanthroline derivative has a higher binding affinity for p32 G-quadruplex than duplex. Further circular dichroism and nuclear magnetic resonance studies indicate that the phenanthroline derivative can regulate p32 G-quadruplex conformation. Real time polymerase chain reaction and luciferase assays show that the phenanthroline derivative has down-modulated Bcl-2 transcription activity in a concentration-dependent manner. However, no such effect was observed when p32 G-quadruplex was denatured through base mutation. Conclusion The newly identified G-quadruplex located in the P1 promoter of Bcl-2 oncogene is intimately related with Bcl-2 transcription activity, which may be a promising anticancer therapeutic target. General significance The newly identified G-quadruplex in the Bcl-2 P1 promoter may be a novel anticancer therapeutic target.

A copper-catalyzed approach for the synthesis of 2-aryl-quinazolinones through a domino reaction involving C–C bond cleavage is described. This protocol involves intramolecular C–C bond cleavage to construct 2-aryl-quinazolinones, which may offer an alternative method to prepare medically important quinazolinone derivatives and a new strategy for C–C bond cleavage. Besides C–C bond cleavage, this domino reaction includes N-arylation and benzylic C–H amidation.

A colorimetric and fluorometric dual-modal supramolecular chemosensor has been fabricated by using the H- and J-aggregates of a cyanine dye, which has been successfully applied to detect human serum albumin (HSA) in urine with high specificity.

A simple technology to construct diverse DNA logic gates (OR and INHIBIT) has been designed utilizing a H(+) and/or Ag(+) induced i-motif structure. The logic gates are easily controlled and also show a real time response towards inputs. The research provides a new insight for designing DNA logic gates using an i-motif DNA structure.

Transferrin has been exploited as a potential drug carrier for targeted drug delivery into cancer cells, which express high levels of transferrin receptors. In the present study, we identified specific structural features in flavonoids that were critical for binding to transferrin. Flavanone naringenin and flavonoid apigenin, two flavonoids with characteristic flavonoid core structures were selected for the study of the effects of C2–C3 single bond in the C-ring on transferrin binding. We determined the binding affinities by fluorescence quenching experiments and investigated the binding modes by CD spectra and molecular modeling. Our results demonstrated that naringenin bound transferrin with an affinity almost 100 times higher than that of apigenin attributed to its higher structural flexibility and lower acidity compared with apigenin. Our docking study showed that naringenin had stronger van der Waals interactions with transferrin, which was believed to contribute to its higher binding affinity. We also found that naringenin-binding induced greater increase in the α-helix content in transferrin than apigenin, suggesting that transferrin became more compact upon association with naringenin. Our study demonstrated that naringenin was a ligand for transferrin with good affinity. The results reported herein can facilitate the design and development of drugs that bind transferrin with high affinity.

As its significant role, the selective recognition of G-quadruplex with specific structures and functions is important in biological and medicinal chemistry. Carbazole derivatives have been reported as a kind of fluorescent probe with many excellent optical properties. In the present study, the fluorescence of the dye (carbazole TO) increased almost 70 fold in the presence of bcl-2 2345 G4 compared to that alone in aqueous buffer condition with almost no fluorescence and 10-30 fold than those in the presence of other DNAs. The binding study results by activity inhibition of G4/Hemin peroxidase experiment, NMR titration and molecular docking simulation showed the high affinity and selectivity to bcl-2 2345 G4 arises from its end-stacking interaction with G-quartet. It is said that a facile approach with excellent sensitive, good selectivity and quick response for bcl-2 2345 G-quadruplex was developed and may be used for antitumor recognition or antitumor agents.

G-quadruplexes attract more and more attention in recent years. Numerous small molecules which can induce or stabilize the formation of G-quadruplexes have been investigated on the purpose of anticancer drug development. As a motif existed in physiological condition, flanking sequences are an important part of G-quadruplexes but the study on the impact of flanking sequences on (G-quadruplex)-ligand binding is rarely reported. In this paper, the effects of flanking sequences on binding affinity between a series of unimolecular parallel-stranded G-quadruplex sequences derived from c-myc oncogene promoter (termed as c-myc G-quadruplexes) and their ligands are discussed in detail. The results showed that the flanking sequences on c-myc G-quadruplexes play key roles in (G-quadruplex)-ligand interaction. When a c-myc G-quadruplex is bound to its ligands, the flanking sequences might form a binding cavity above the terminal G-quartet, which could provide a suitable site for ligands to dock in. Moreover, the bases on flanking sequences could interact with ligand through π-π stacking, and finally form a sandwich-stacking mode (terminal G-quartet, ligand and bases on the flanking sequence). This mode could stabilize the (G-quadruplex)-ligand complex effectively and enhance the binding affinity dramatically. However, flanking sequences are also found to exhibit steric hindrance effect which could impede the (G-quadruplex)-ligand binding.

Here we report that an excess amount of aldehyde, in particular, aliphatic aldehyde, without any additives, efficiently facilitates the oxidation of aminal intermediates to quinazolinones in pure water.

Burkitt lymphoma (BL) is a rare and highly aggressive type of non-Hodgkin lymphoma. The mortality rate of BL patients is very high due to the rapid growth rate and frequent systemic spread of the disease. A better understanding of the pathogenesis, more sensitive diagnostic tools and effective treatment methods for BL are essential. Metabolomics, an important aspect of systems biology, allows the comprehensive analysis of global, dynamic and endogenous biological metabolites based on their nuclear magnetic resonance (NMR) and mass spectrometry (MS). It has already been used to investigate the pathogenesis and discover new biomarkers for disease diagnosis and prognosis. In this study, we analyzed differences of serum metabolites in BL mice and normal mice by NMR-based metabolomics. We found that metabolites associated with energy metabolism, amino acid metabolism, fatty acid metabolism and choline phospholipid metabolism were altered in BL mice. The diagnostic potential of the metabolite differences was investigated in this study. Glutamate, glycerol and choline had a high diagnostic accuracy; in contrast, isoleucine, leucine, pyruvate, lysine, α-ketoglutarate, betaine, glycine, creatine, serine, lactate, tyrosine, phenylalanine, histidine and formate enabled the accurate differentiation of BL mice from normal mice. The discovery of abnormal metabolism and relevant differential metabolites may provide useful clues for developing novel, noninvasive approaches for the diagnosis and prognosis of BL based on these potential biomarkers.

The indolizinones are synthesized from pyridine ketones and terminal alkynes following a propargylation/cyclization/1,2-migration sequence.

G-quadruplexes have attracted growing attention as a potential cancer-associated target for both treatment and detection in recent years. For detection purpose, high specificity is one of the most important factors to be considered in G-quadruplex probe design. It is well known that end stacking and groove binding are two dominated quadruplex-ligand binding modes, and currently most reported G-quadruplex probes are designed based on the former, which has been proven to show good selectivity between quadruplexes and non-quadruplexes. Because groove of G-quadruplex also has some unique chemical properties, it could be inferred that probes that can interact with both the groove and G-tetrad site of certain G-quadruplexes simultaneously might possess higher specificity in aspects of discriminating different quadruplexes. In this article, we report a cyanine dye as a potential novel probe scaffold that could occupy both the 5′-end external G-tetrad and the corresponding groove of the G-quadruplex simultaneously. By using various spectrum and nuclear magnetic resonance techniques, we give a detailed binding characterization for this dual-site simultaneous binding mode. A preliminary result suggests that this mode might provide highly specific recognition to a parallel-stranded G-quadruplex. These findings and the structural elucidation might give some clues in aspects of developing highly specific G-quadruplex probes.

The G-quadruplex ligands database (G4LDB, http://www.g4ldb.org) provides a unique collection of reported G-quadruplex ligands to streamline ligand/drug discovery targeting G-quadruplexes. G-quadruplexes are guanine-rich nucleic acid sequences in human telomeres and gene promoter regions. There is a growing recognition for their profound roles in a wide spectrum of diseases, such as cancer, diabetes and cardiovascular disease. Ligands that affect the structure and activity of G-quadruplexes can shed light on the search for G-quadruplex-targeting drugs. Therefore, we built the G4LDB to (i) compile a data set covering various physical properties and 3D structure of G-quadruplex ligands; (ii) provide Web-based tools for G-quadruplex ligand design; and (iii) to facilitate the discovery of novel therapeutic and diagnostic agents targeting G-quadruplexes. G4LDB currently contains >800 G-quadruplex ligands with ∼4000 activity records, which, to our knowledge, is the most extensive collection of its kind. It offers a user friendly interface that can meet a variety of data inquiries from researchers. For example, ligands can be searched for by name, molecular properties, structures, ligand activities and so on. Building on the reported data, the database also provides an online ligand design module that can predict ligand binding affinity in real time.

Inhibition of the α-glucosidase activity is a therapeutic approach for diabetes. In this study, an effective strategy for screening α-glucosidase inhibitors based on Nuclear magnetic resonance (NMR) techniques was developed to screen and identify α-glucosidase inhibitors from Mulberry leaf extract. As a result, deoxynojirimycin, as a potential α-glucosidase inhibitor, was found. The study suggested that our strategy was a powerful tool for screening and identification of α-glucosidase inhibitors in complex samples. Furthermore the interaction between α-glucosidase and its inhibitor was studied by NMR.

Calixaromatics have attracted much attention on molecular recognition owing to their flexible conformations, cavity structures, versatile recognition properties, and functions. However, conformational control of calixaromatics is still a challenging topic in the field of calixaromatics. Therefore, we explore the possibility to control the chirality of achiral calixaromatics, methylazacalix[6]pyridine (abbreviated as MACP6), by templating of DNA. We have found that MACP6 with opposite chirality can be achieved by controlling the secondary structure of bcl-2 2345 DNA. Furthermore, MACP6 with different chirality has been used to recognize fullerene derivatives in aqueous solution. Our results have provided a possible approach to construct chiral calixaromatics.

Telomeres are important multifunctional nucleoprotein structures located at the ends of eukaryotic chromosomes. Telomerase regulates telomere elongation, and its activity is associated with tumorigenesis. Because the activity of telomerase can be inhibited by G-quadruplex (G4) formation (a four-stranded DNA with stacks of G-quartets formed by four guanines in a planar structure), the role of G4 in cancer therapy has attracted many research interests. We studied the effects of three natural alkaloids-tetrandrine, fangchinoline, and berbamine-on the stability and formation of telomere DNA G4 with circular dichroism melting spectroscopy (melting-CD), variable temperature ultraviolet (melting-UV), proton nuclear magnetic resonance spectroscopy ((1)H NMR), and molecular docking, and examined the relationships among the alkaloid structure and their activities. We further investigated their cytotoxicity with the 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide assay (MTT) and flow cytometry (FCM). The results demonstrated that alkaloids increased G4 stability and induced its formation, which added structure diversity of G4-ligands. The results showed that -OH at R(1), -OCH(3) at R(2), and [Formula: see text] at R(3) had higher stability than other substituent groups for these alkaloids. We also found a transition of antiparallel to parallel G4 as the temperature increased. The result indicated the possible advantage of parallel G4 in adversity. In addition, the alkaloids demonstrated a moderate cytotoxicity and proved to be cell cycle blocker in the G(1) phase. These alkaloids have revealed promising potentials to be the agents for antitumor therapy.

A novel trend in G-quadruplex ligand design is to build a binder that is able to not only discriminate G-quadruplex from duplex-DNA, but also among various G-quadruplex structures. Methylazacalix[6]pyridine (MACP6), a new type of azacalixarene with flexible conformation, exhibits induced circular dichroism signals when interacted with most of G-quadruplexes. The intensities of the induced signals are strongly dependent on the topology of G-quadruplexes. Further evidence has shown that these signals can be ascribed to the preferred binding of MACP6 to the loops of G-quadruplexes, which rely on the nature of nucleotides in the loops.

Screening G-quadruplex ligands from natural plants is important because the ligands may be potential antitumor drugs. A new screening strategy is proposed based on the combination of dialysis and G-quadruplex recognition technique which could separates G-quadruplex ligand from natural extracts and elucidate the structure of this ligand. This result offers a novel approach to obtain active antitumor compounds.

In order to investigate the effect of PEO-PPO-PEO copolymers on the glutathione (GSH)/glutathione-S-transferase (GST) detoxification system, interaction between the copolymers and GSH is studied by NMR measurements. Selective rotating-frame nuclear Overhauser effect (ROE) experiment confirms that glutamyl (Glu) alpha-H of GSH has spatial contact with EO methylene protons. Spin-lattice relaxation times of GSH Glu alpha-H show a decrease when PEO-PPO-PEO copolymers are added, and the decrease is greater with copolymers possessing more EO units. Other protons of GSH show little change in the presence of the copolymers. The addition of GSH promotes the dehydration of PEO-PPO-PEO copolymers. This results from the breaking of hydrogen bonds between water and the polymers and the forming of hydrogen bonds between Glu alpha-carboxylate protons and oxygen atoms of EO units. The dissociation constant between GSH and P85 copolymer is determined by spin-lattice relaxation measurements, which shows the binding is Of low affinity and the two molecules are in fast dissociation kinetics. This study suggests that GSH transporting or utilizing systems may be affected by treatment of PEO-PPO-PEO copolymers.

Single-stranded telomeric DNA tends to form a four-base-paired planar structure termed G-quadruplex. Although kinds of G-quadruplex structures in vitro have been documented in the presence of potassium or sodium, recognition of these DNA motifs (both in vitro and in vivo) is still an important issue in understanding the biological function of the G-quadruplex structures in telomeres as well as developing anticancer agents. Herein we address this important question through the distinctive properties of a supramolecular system of cyanine dye 3,3′-di(3-sulfopropyl)-4,5,4′,5′-dibenzo-9-methyl-thiacarbocyanine triethylammonium salt (MTC) upon binding to different DNA motifs. Interaction of MTC with hybrid/mixed G-quadruplex results in a set of unique spectrophotometric signatures which are completely different from those arising from binding to other DNA motifs. Furthermore, such feature could be extended to map the locations of DNAs on interface. Linear duplex and mixed G-quadruplex in human telomeres assembled on Au film and stained by MTC were directly recognized by confocal laser scanning microscopy (CLSM). All results suggested that MTC supramolecular system may be a good probe of specific G-quadruplex structure.

The ligands which can facilitate the formation and stabilize G-quadruplex structures have attracted enormous attention due to their potential ability of inhibiting the telomerase activity and halting tumor cell proliferation. It is noteworthy that the abilities of the quaternary benzophenanthridine alkaloids (QBAs), the very important G-quadruplex binders, in inducing the formation of human telomeric DNA G-quadruplex structures, have not been reported. Herein, the interaction between single-strand human telomeric DNA and three QBAs: Sanguinarine (San), Nitidine (Nit) and Chelerythrine (Che), has been investigated. Although these molecules are very similar in structure, they exhibit significantly different abilities in inducing oligonucleotide d(TTAGGG)4 (HT4) to specific G-quadruplex structures. Our experimental results indicated that the best ligand San could convert HT4 into antiparallel G-quadruplex structure completely, followed by Nit, which could transform to mixed-type or hybrid G-quadruplex structure partially, whereas Che could only transform to antiparallel G-quadruplex structure in small quantities. The relative QBAs' inducing abilities as indicated by the CD data are in the order of San>Nit>Che. Further investigation revealed that the G-quadruplex structures from HT4 induced by QBAs are of intramolecular motif. And only sequences with certain length could be induced by QBAs because of their positive charges which could not attract short chain DNA molecules to close to each other and form intermolecular G-quadruplex. In addition, the factors that affect the interaction between HT4 and QBAs were discussed. It is proposed that the thickness of the molecular frame and the steric hindrance are the primary reasons why the subtle differences in QBAs' structure lead to their remarkable differences in inducing the formation of the G-quadruplex structures.

Cancer threatens human health, thus research focusing on oncology has great significance. Metabonomics is the global quantitative assessment of the dynamic metabolic response of a biological system to some exogenous or genetic pathophysiological perturbation. The metabolites are detected in tissues or fluids by various analytical methods, such as nuclear magnetic resonance (NMR) and mass spectroscopy. Metabonomics, as a tool, can provide a link between the laboratory and clinic. NMR-based metabonomics offers a useful tool to understand tumour biochemistry and may also has some potentials for tumour diagnosis and prognosis, even when some other disease processes are present. Here, we review NMR-based metabonomics principles and their applications in oncology research.

The supramolecular assembly of a novel cyanine dye, 3,3'-di(3-sulfopropyl)-4,5,4',5'-dibenzo-9-ethyl-thiacarbocyanine triethylammonium salt (ETC) was designed to verify specific intramolecular G-quadruplexes from duplex and single-strand DNAs. Spectral results have shown that ETC presented two major distinct signatures with specific intramolecular G-quadruplexes in vitro: (i) dramatic changes in the absorption spectra (including disappearance of absorption peak around 660 nm and appearance of independent new peak around 584 nm); (ii) approximately 70 times enhancement of fluorescence signal at 600 nm. Furthermore, based on (1)H-nuclear magnetic resonance and circular dichroism results, the preferring binding of ETC to specific intramolecular G-quadruplexes probably result from end-stacking, and the loop structure nearby also plays an important role.

Human DNA sequences consisting of tandem guanine (G) nucleotides can fold into a four-stranded structure named G-quadruplex via Hoogsteen hydrogen bonding. As the sequences forming G-quadruplex exist in essential regions of eukaryotic chromosomes and are involved in many important biological processes, the study of their biological functions has currently become a hotspot. Compounds selectively binding and stabilizing G-quadruplex structures have the potential to inhibit telomerase activity or alter oncogene expression levels and thus may act as antitumor agents. Most of reported G-quadruplex ligands generally have planar structures which stabilize G-quadruplex by pi-pi stacking. However, based on a pharmacophore-based virtual screening two non-planar G-quadruplex ligands were found. These two ligands exhibit good capability for G-quadruplex stabilization and prefer binding to paralleled G-quadruplex rather than to duplex DNA. The binding of these ligands to G-quadruplex may result from groove binding at a 2:1 stoichiometry. These results have shown that planar structures are not essential for G-quadruplex stabilizers, which may represent a new class of G-quadruplex-targeted agents as potential antitumor drugs.

A single-stranded G-tract human telomere DNA sequence is able to fold into intramolecular G-quadruplex structures which may be important for a number of biological processes and disease-related mechanisms. Poly(L-lysine) (PLL) polymer is linear polypeptides with lysine as the repeat unit and has been employed as a gene carrier in achieving targeted delivery of DNA to cancer cells. To explore the influence of PLL on the conformation of Hum24 DNA, we have investigated the interaction of PLL with Hum24 by biophysical methods, mainly CD, ESI-MS, and polyacrylamide gel electrophoresis for the first time. The CD data have shown that PLL can induce single-stranded Hum24 to form an intramolecular parallel G-quadruplex structure, further confirmed by ESI-MS analysis and gel electrophoresis results. The formation of an intramolecular G-quadruplex is strongly dependent on the Hum24/PLL molar ratios and the length of both the polypeptides and oligonucleotide. Such phenomena may be interpreted by electrostatically attracting negative-charged Hum24 by positive-charged PLL which facilitates the close contact between the guanines and formation of hydrogen bonding, thus leading the final shape of a G-quadruplex structure.

Based on the recognition of bio-target molecules, screening novel anti-cancer drugs has become one of the research focuses. The revealing of the relationship between the G-quadruplex and cancer by modern molecular biology techniques provides a new opportunity to the anti-cancer drugs research. A general consensus is that organic molecules that induce or stabilize G-quadruplex structures could pave the way for the discovery of novel anti-cancer agents. Therefore, it attracts the interest of chemists and biologists in the research on anticancer drug structure screening and rational design target in G-quadruplex. The present article aims to highlight recent advances in the screening and design of G-quadruplex ligands and development of the anticancer drugs. Firstly, two screening ap-proaches based on the recognition of G-quadruplex are introduced, one is fast screening of G-quadruplex ligands from natural plant extracts based on NMR, the other is screening anticancer compounds by molecular docking techniques. Secondly, the numerous ligands can be classified into four different categories on the basis of their cationic nature, (1) in situ protonation of an amine ap-pendage, (2) N-methylation of an aza-aromatic moiety, (3) the presence of a metal centre, and (4) noncationic ligands. Finally, two quadruplex-related drug candidates CX3543 and AS1411 have en-tered phase I clinical trial, and the mechanism of them has been explored.

A series of gemini amphiphiles (bis(2'-heptadecyl-3'-ethylimidazolium)-1,n-alkane dibromide, abbreviated as Gn, n = 2, 4, 6, 8, 10) was found to form vesicles under ultrasonication in aqueous solution at very low concentration (5 microM), which was confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The adsorption and interaction of a cyanine dye (3,3'-disulfopropyl-4,5,4',5'-dibenzo-9-methyl-thiacarbocyanine triethylammonium salt, abbreviated as MTC) on the vesicles was investigated. It was found that the cyanine dye could exhibit different colors when interacting with the vesicles. The UV-vis spectral measurements revealed the formation of the H or J aggregates of the cyanine dye on the vesicles, which is spacer length dependent: the short spacer length prefers the formation of the H-aggregate, whereas the longer spacer favors the J-aggregate formation. In addition, these aggregates showed different absorption positions from those on the planar films. Furthermore, by mixing the G2 and G10 vesicles in different ways, the selective aggregation of the cyanine dye on the vesicles was realized.

The studies on the interaction between HSA and drugs have been an interesting research field in life sciences, chemistry and clinical medicine. There are also many metal ions present in blood plasma, thus the research about the effect of metal ions on the interaction between drugs and plasma proteins is crucial. In this study, we have investigated the effect of a familiar metal ion-Cu 2+ on the interaction between an antitumor drug–mitoxantrone (MTO) and human serum albumin (HSA) by using fluorescence spectroscopy, ultraviolet–visible absorption spectroscopy and circular dichroism spectroscopy, for the first time. The results showed that the quenching efficiency of MTO to HSA is higher with Cu 2+ than that without Cu 2+ . In the presence of Cu 2+ , the secondary structure of HSA was changed and the α-helix content was increased. The apparent association constant ( K A ), the binding sites ( n ) and the spatial-distance ( r ) between MTO and HSA decreased. These results indicated that Cu 2+ could affect the interaction between MTO and HSA by altering HSA molecular conformation. Further calculation indicated that the binding mode of Cu 2+ in MTO–HSA system was likely to form Cu 2+ –HSA complex.

Aloe dihydroisocoumarin, one of new components isolated from Aloe vera, can scavenge reactive oxygen species. In order to explore the mechanism of drug action at a molecular level, the binding of Aloe dihydroisocoumarin with human serum albumin (HSA) has been investigated by using fluorescence, ultraviolet (UV), circular dichroism (CD) and Fourier transform infrared (FT-IR) spectroscopy, fluorescence dynamics, and molecular dynamic docking for the first time. We observed a quenching of fluorescence of HSA in the presence of Aloe dihydroisocoumarin and also analyzed the quenching results using the Stern–Volmer equation and obtained high affinity binding to HSA. An isoemissive point at 414 nm is seen, indicating that the quenching of HSA fluorescence depends on the formation of Aloe dihydroisocoumarin-HSA complex, which is further confirmed by fluorescence dynamic result. From the CD and FT-IR results, it is apparent that the interaction of Aloe dihydroisocoumarin with HSA causes a conformational change of the protein, with the gain of α-helix, β-sheet and random coil stability and the loss of β-turn content. Data obtained by fluorescence spectroscopy, fluorescence dynamics, CD, and FTIR experiments along with the docking studies suggest that Aloe dihydroisocoumarin binds to residues located in subdomain IIA of HSA.

Aloe dihydrocoumarin is an antioxidant and a candidate of immunomodulatory drug on the immune system and can balance physiological reactive oxygen species (ROS) levels which may be useful to maintain homeostasis. In order to explore the mechanism of drug action at a molecular level, the binding of Aloe dihydrocoumarin with human serum albumin (HSA) has been investigated by fluorescence, ultraviolet (UV), circular dichroism (CD) and Fourier transform infrared (FT-IR) spectroscopy, fluorescence dynamics, and molecular dynamic docking for the first time. We observed a quenching of fluorescence of HSA in the presence of Aloe dihydrocoumarin and also analyzed the quenching results using the Stern–Volmer equation and obtained high affinity binding to HSA. A Forster type fluorescence resonance energy transfer mechanism is involved in this quenching of Trp fluorescence by Aloe dihydrocoumarin. From the CD and FT-IR results, it is apparent that the interaction of Aloe dihydrocoumarin with HSA causes a conformational change of the protein, with the loss of α-helix stability and the gain of β-sheet and β-turn content. Data obtained by fluorescence spectroscopy, fluorescence dynamics, CD, and FT-IR experiments along with the docking studies suggest that Aloe dihydrocoumarin binds to residues located in subdomain IIA of HSA.

The interaction of a novel pesticide, NMD (spiro[(2 R ,3 R ,4 S )-4-benzyloxy-2,3-iso-propylidenedioxy-1-oxacyclopentane-5,5′-(2-nitromethylene-1,3-diazacyclohexane)]), with bovine serum albumin (BSA) has been investigated by using absorption, fluorescence, and circular dichroism (CD) spectroscopy methods. Quenching of the fluorescence of BSA has been observed in the presence of NMD. The binding parameters were determined using Stern–Volmer equation. From the thermodynamic parameters calculated according to the van’t Hoff equation, the enthalpy change Δ H , and entropy change Δ S were found to be −2.71 kJ mol −1 and 82.56 J mol −1 K −1 , respectively. These values suggested that, apart from an initial hydrophobic association, the complex is held together by van der Waals interactions and hydrogen bonding. These results provided a quantitative understanding of the binding of NMD to BSA, which is important in understanding its toxicity in vertebrates.

A potential targeting drug delivery system consisting of folate (FA), the targeting molecule, human serum albumin (HSA), the carrier, and mitoxantrone (MTO), the medicine, has been designed. Data obtained by UV absorption, fluorescence, and NMR techniques indicated the formation of ternary complexes and possible application to building a targeting drug delivery system by using FA, MTO and HSA. Furthermore, cytotoxicity assay indicated that the toxicity of the FA-HSA-MTO against PC-3 cell line was 79.95%, which was much higher than that of free MTO tested in totally the same conditions. About 30% increase of the toxicity should be owed to the targeting effect of FA. Thus, the feasibility and validity of a novel targeting drug delivery system, FA-HSA-MTO, was confirmed.

The effects of conformational changes to transferrin induced by the binding of flavonoids with different numbers and positions of hydroxyl groups were explored using spectroscopic and molecular modeling methods. The flavonoid hydroxyl group is not necessary for conformation changes of transferrin. However, the binding ability was found to increase with increasing numbers of hydroxyl groups and further conformational changes were observed. By molecular modeling calculations, intermolecular energy including van der Waals and electrostatic interactions, together with hydrogen bonding are found to have important roles in binding of flavonoids to transferrin. Additionally, the positions of the hydroxyl groups also affect the binding ability because they can alter the relative acidity of the hydroxyl groups, thereby changing the hydrogen bonding ability. Our results have indicated a mechanism for the interactions between flavonoids and transferrin, and provide information for possible flavonoid modification and design of methods to deliver drug molecules via transferrin to target tissues and cells effectively.

The interactions of a cyanine dye with human serum albumin (HSA) and bovine serum albumin (BSA) have been investigated by using absorption and fluorescence spectra. Absorption spectral studies show that binding to the serum albumins leads to a bathochromic shift of the monomer band together with a notable intensity change. Furthermore, the number of binding sites (n) was identified by the absorption spectra. There is a constant enhancement of fluorescence quantum yield when the cyanine dye complexes with HSA or BSA. The apparent binding constant (Ka) and the free energy changes (ΔG) were obtained by analysis of fluorescence data of the cyanine dye in the absence and presence of HSA and BSA. Compared to BSA, HSA associates with the dye in a stronger way.

Single-crystal Sb doped ZnO nanowires were fabricated on Si (1 0 0) substrate by a chemical vapor deposition method. The photoluminescence properties of ZnO nanowires were studied with the temperature ranging from 81 to 306 K. At 81 K, the recombination of the acceptor-bound exciton was predominant in PL spectrum, which was attributed to the transition of the (SbZn–2VZn) complex bound exciton. The activation of A0X and the acceptor binding energy had been calculated to be 16.8 and 168 meV, respectively.

The J-aggregation behaviour of two cyanine dyes (3,3′-disulfopropyl-4,5,4′,5′-dibenzo-9-methyl-thiacarbocyanine triethylammonium salt ( MTC ) and 3,3′-disulfopropyl-4,5,4′,5′-dibenzo-9-phenyl-thiacarbocyanine triethylammonium salt ( PTC )) has been investigated in the presence of dication chloride using absorption spectroscopy, 1 H and multinuclear NMR methods. The promotion efficiency on J-aggregation of the dye molecule and the magnitude of the effective coherence length of the J-aggregate were found to be dependent on the dyes' structure and their ability to coordinate with the metal ions. The interaction between the metal ions and the J-aggregates could be explained by the association between metal ions and J-aggregates, and the apparent association constants were obtained from the chemical shifts in NMR spectra of the metal ions.

The interaction between a novel promising drug (spiro[(2 R ,3 R ,4 S )-4-benzyloxy-2,3-isopropylidene-dioxy-1-oxa-cyclopentane-5,5′-(2-benzoylmethylene-1,3-diaza-cyclohexane)] (SBDC)) and human serum albumin (HSA) under physiological conditions has been investigated by using fluorescence, absorption, and circular dichroism (CD) spectroscopic techniques in combination with protein–ligand docking study. It was observed that SBDC has a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. The association constants of SBDC with HSA were determined at different temperatures based on fluorescence quenching results. The negative Δ H and positive Δ S values in case of SBDC–HSA complex showed that apart from an initial hydrophobic association, both van der Waals interactions and hydrogen bonding play a vital role in the binding of SBDC to HSA. The quantitative analysis data of CD spectra showed that the binding of SBDC to HSA induced conformational changes in HSA and the α-helix of 52.1% in free HSA increased to 55.7% in HSA–SBDC complex. The distance between donor (HSA) and acceptor (SBDC) was obtained according to the Forster's theory of non-radiation energy transfer. Data obtained by spectroscopic techniques and protein–ligand docking study suggested that SBDC binds to residues located in subdomain IIA of HSA.

The action mechanism of vanadocene dichloride, Cp2VCl2 (Cp=eta5-C5H5), has been investigated by interaction with human serum transferrin for its promising antitumor activities. Our results have shown that Cp2VCl2 binds to transferrin and form a new complex, and the calculated apparent association constant is 1.37 x 10(5)M(-1) from the fluorescence quenching. Simultaneously, the variation of the secondary structure of transferrin occurs, most probably due to the coordination of the amino residues of protein with VIV. It was evidenced that Cp is released free in solution after VIV binding to transferrin by 1H NMR measurements. These results have shown that Cp2VCl2 forms a complex with transferrin, which may provide a possible pathway in the transport and targeted delivery of the antitumor agent.

Metabonomics analysis of the urine of rats with Qi deficiency and blood stasis syndrome has been performed by comparison with those of normal rats based on NMR techniques. The relative contents of formate, creatinine, 2-oxoglutarate (2-OG), citrate, taurine, trimethylamine-N-oxide(TMAO), succinate and hippurate in the urine of the rats with Qi deficiency and blood stasis syndrome have been changed. These results have provided evidence for understanding the mechanism and the therapy of Qi deficiency and blood stasis syndrome.

Water-soluble fullerene derivatives have attracted great attention in biological and medical applications. In particular, for any potential in vivo application, the interaction of water-soluble fullerene nanoparticles with human serum albumin (HSA) is crucial. In this study, we synthesized a novel organophosphate-containing water-soluble derivative of C60 (C60Om(OH)n(C(PO3Et2)2)l (m ≈ 8, n ≈ 12, and l ≈ 1), abbreviated as TEMDP-CF). To explore the influence of an organophosphate-containing water-soluble derivative of C60 nanoparticles on the conformational changes of HSA, we have investigated the interaction of TEMDP-CF with HSA by biophysical methods, mainly 31P NMR, MALDI-TOF mass spectroscopy, fluorescence, fluorescence dynamics, UV spectroscopy, FT-IR, and CD, for the first time. 31P NMR and MALDI-TOF MS analysis have proven the formation of the HSA−TEMDP-CF complex, which is further confirmed by fluorescence and fluorescence dynamics results. We observed a quenching of fluorescence of HSA in the pres...

H-1 nuclear magnetic resonance (NMR) spectroscopy has been applied to study the temperature and concentration-induced micellization of a poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) triblock copolymer, Pluronic P105, in D2O solutions in the temperature range from 5 to 45 degrees C and the concentration range from 0.01 to 15% (w/v). The intrinsic probes, the chemical shift, and the half-height width of the PO -CH3 signal are very sensitive to the local environment and can be used to characterize the temperature and concentration-dependent aggregation process. When the temperature approaches the critical micellization temperature or the polymer concentration reaches the critical micellization concentration, the chemical shift of the PO -CH3 signal moves toward lower ppm values and the half-height width of the PO -CH3 signal shows a sudden increase. It indicates that the methyl groups are experiencing a progressively less polar environment and transferring from water to the hydrophobic micellar core. The hydrodynamic radius of the unimers and the micelles are determined as be 1.8 and 5.0 nm by means of pulsed-field gradient spin-echo (PGSE) NMR. They were independent of temperature and concentration. The drastic shortening of spin-lattice relaxation time T-1 for the PO -CH3/-CH2- protons in the transition region suggested that the PPO blocks are located in a "liquid-like" micellar core, whereas the exponential increase of T-1 for the PEO -CH2- protons implied that the PEO blocks are still keeping in contact with surrounding water. Thermodynamics analysis according to a closed association model shows that the micellization process is entropy-driven and has an endothermic micellization enthalpy. (c) 2007 Elsevier Inc. All rights reserved.

The interactions of three cyanine dyes, which exhibit different meso substituent in polymethine chain, with human serum albumin (HSA) have been investigated by the means of absorption, fluorescence and circular dichroism (CD) spectra. In phosphate buffer solution (PBS), the mentioned dyes exist not as isolated monomers but rather in the formation of J-aggregation. In the presence of HSA, the absorption and fluorescence emission spectra indicated that the J-aggregation was decomposed to monomer because of the strong affinity between dye molecules and HSA. Besides the association of cyanine dyes with HSA, binding to HSA gave rise to the J-aggregation CD signals. The meso substituent in the polymethine plays an important role in the interaction of HSA and the J-aggregation. Spectral studies showed that the dye bound with HSA in a 1:1 formation. The apparent constant (K(a)) value was roughly identified by analysis of the corresponding fluorescence data at various HSA concentrations. The higher affinity of the molecule with meso phenyl towards HSA with respect to molecules with meso ethyl or methyl can be attributed to the arrangement of molecules in J-aggregation and the hydrophobic force between the molecules and HSA.

The effects of three diosgenyl saponins isolated from Paris polyphylla on the immuno-stimulating activity in relation to phagocytosis, respiratory burst, and nitric oxide production in mouse macrophage cells RAW 264.7 have been investigated. Our results showed that all three diosgenyl saponins significantly enhanced phagocytic activity that increased with the concentration of saponins to reach a maximum, and then tended to decrease with higher concentrations. Saponins with sugar moiety directly induced respiratory burst response in RAW 264.7 cells that increased with the concentrations and reached a maximum, then decreased with higher concentrations after 2-h incubations, however, diosgenin had no PMA-triggered respiratory burst response. Treatment of RAW 264.7 cells with saponins with sugar moiety for 24-h caused a significant increase in the production of nitric oxide, while diosgenin had no effect at all. Consequently, relationship between molecular structures of three diosgenyl saponins and their immunomodulatory activities was discussed, and a possible mechanism of immuno-stimulating function of diosgenyl saponins was accordingly explored.

Solution H-1 NMR techniques were used to characterize the interaction of urea with poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers. The urea was established to interact selectively with the PEO blocks of the block copolymer, and the interaction sites were found not to change with increasing temperature. Such interactions influence the self-assembly properties of the block copolymer in solution by increasing the hydration of the block copolymers and stabilizing the gauche conformation of the PPO chain. Therefore, urea increases the critical micellization temperature (CMT) values of PEO-PPO-PEO copolymers, and the effect of urea on the CMT is more pronounced for copolymers with higher PEO contents and lower for those with increased contents of PPO segments.

Sinomenine, an herbal ingredient isolated from Sinomenium acutum, is used for the amelioration of arthritis. It has been found that this molecule could bind to human serum transferrin (Tf), the iron (III) transport protein in the blood, by using fluorescence, circular dichroism (CD) spectroscopy, and molecular modeling methods. The results provide possible usage of transferrin to transport sinomenine.

An aqueous micellar solution of a PEO-PPO-PEO triblock copolymer, pluronic F88 (EO103PO39EO103), in the presence of salt (KCl) has been investigated by H-1 NMR spectroscopy. The hydrogen-bonding structure in water is directly changed by the strong polarization effect of added salt, which indirectly weakens the interaction of polymer molecules with water. Both EO and PO blocks are dehydrated by the addition of salt in a similar way, whereas the solubility of the PO blocks may be affected in a more pronounced way, which results in the decrease of the critical micellization temperature (CMT). It is found that the addition of salt favors a more compact micellar core, where the water content is decreased and an effective PO-PO interaction is increased. Increasing the salt concentration would result in a decrease in the number of gauche conformers in the PPO chain, which may be the deeper reason for the decreasing solubility of PPO segments in aqueous salt solution. The temperature region over which the micellization occurs is broad, indicating that micelles and unimers coexist over an extended temperature range, whereas this transition region is significantly narrowed by the addition of salt. The addition of salt offers a good substitute way of changing the temperature to induce micellization. The critical micellization salt concentration (CMSC) is determined to be 1.0 mol l(-1) for KCl in 2.5% aqueous pluronic F88 solution at 25 degrees C, and the transition region in which both free and associated copolymer molecules coexist is defined to range from 1 to 2 mol L-1.