Glycation and drug binding by serum albumin.

Accumulation of glycation products in patients with hyperglycaemic conditions can lead to their reaction with the proteins in the human system such as serum albumin, haemoglobin, insulin, plasma lipoproteins, lens proteins and collagen among others which have important biological functions. Therefore, it is important to understand if glycation of these proteins affects their normal action not only qualitatively, but also importantly quantitatively. Glycation of human serum albumin can easily be carried out over period of weeks and its drug transportability may be examined, in addition to characterisation of the amadori products. A combination of ultrasensitive isothermal titration calorimetry, differential scanning calorimetry, spectroscopy and chromatography provides structure-property-energetics correlations which are important to obtain mechanistic aspects of drug recognition, conformation of the protein, and role of amadori products under conditions of glycation. The role of advance glycation end products is important in recognition of antidiabetic drugs. Further, the extent of glycation of the protein and its implication on drug transportability investigated by direct calorimetric methods enables unravelling mechanistic insights into role of functionality on drug molecules in the binding process, and hinderance in the recognition process, if any, as a result of glycation. It is possible that the drug binding ability of the protein under glycation conditions may not be adversely affected, or may even lead to strengthened ability. Rigorous studies on such systems with diverse functionality on the drug molecules is required which is essential in deriving guidelines for improvements in the existing drugs or in the synthesis of new molecular entities directed towards addressing diabetic conditions.

Binding and displacement study of gentamicin, 5-fluorouracil, oxytetracycline and rolitetracycline with (BSA: Drug2) complex using spectroscopic and calorimetric techniques: Biophysical approach.

Understanding of energetics of interactions between drug and protein is essential in pharmacokinetics and pharmacodynamics study. The binding affinity (K) helps in investigating how tightly or loosely drug is bound to protein. The binding, displacement, conformational change and stability study of drugs- gentamicin (GM), 5-fluorouracil (5FU), oxytetracycline (OTC) and rolitetracycline (RTC) with bovine serum albumin (BSA) has been carried out in presence of each other drug by fluorescence, UV-visible spectroscopy, molecular docking, circular dichroism techniques and thermal denaturation method. The site marker study and docking methods have confirmed that 5FU and GM are able to bind at site 1 and OTC and RTC at site II of BSA. The order of their binding affinities with BSA for the binary system were as GM <5FU < OTC < RTC with the order of 102 < 103 < 105 < 105-6 M-1. The displacement study has shown that higher affinity drug decreases the equilibrium constant of another drug already in bound state with BSA if both these drugs are having the same binding site. Therefore 5FU, GM (binding site 1) drugs were not able to displace OTC and RTC (binding site 2) and vice-versa as they are binding at two different sites. The binding constant values were found to be decreasing with increasing temperature for all the systems involved which suggests static or mixed type of quenching, however can only confirmed with the help of TCSPC technique. The ΔG0 (binding energy) obtained from docking method were in accordance with the ITC method. From molecular docking we have determined the amino acid residues involved in binding process for binary and ternary systems by considering first rank minimum binding energy confirmation. From CD it has been observed that RTC causes most conformational change in secondary and tertiary structure of BSA due to the presence of pyrrole ring. OTC-RTC with higher affinity showed highest melting temperature Tm values while low affinity drugs in (5FU-GM) combination showed lowest Tm value. 5FU showed large endothermic denaturation enthalpy ΔHd0 due to the presence of highly electronegative fluorine atom in the pyridine analogue.

Analytical Aspects of ANSA-BSA Association: A Thermodynamic and Conformational Approach.

Many studies have demonstrated the manner in which ANS interacts with bovine serum albumin (BSA), although they are limited by the extremely low solubility of dye. The present study demonstrates the binding of ANSA dye with BSA, and since this dye can easily replace ANS, it not only simplifies research but also improves sensor accuracy for serum albumin. A combination of calorimetry and spectroscopy has been employed to establish the thermodynamic signatures associated with the interaction of ANSA with the protein and the consequent conformational changes in the latter. The results of differential scanning calorimetry reveal that when the concentration of ANSA in solution is increased, the thermal stability of the protein increases substantially. The fluorescence data demonstrated a decrease in the binding affinity of ANSA with the protein when pH increased but was unable to identify a change in the mode of interaction of the ligand. ITC has demonstrated that the mode of interaction between ANSA and the protein varies from a single set of binding sites at pH 5 and 7.4 to a sequential binding site at pH 10, emphasizing the potential relevance of protein conformational changes. TCSPC experiments suggested a dynamic type in the presence of ANSA. Molecular docking studies suggest that ANSA molecules are able to find ionic centers in the hydrophobic pockets of BSA. The findings further imply that given its ease of use in experiments, ANSA may be a useful probe for tracking the presence of serum albumin and partially folded protein states.

pH-dependent interactions of biologically important metal ions with hen egg white lysozyme based on its hydration properties: Thermodynamic and mechanistic insights.

Importance of metal ion selectivity in biomolecules and their key role in proteins are widely explored. However, understanding the thermodynamics of how hydrated metal ions alter the protein hydration and their conformation is also important. In this study, the interaction of some biologically important Ca2+, Mn2+, Co2+, Cu2+, and Zn2+ ions with hen egg white lysozyme at pH 2.1, 3.0, 4.5 and 7.4 has been investigated. Intrinsic fluorescence studies have been employed for metal ion-induced protein conformational changes analysis. Thermostability based on protein hydration has been investigated using differential scanning calorimetry (DSC). Thermodynamic parameters emphasizing on metal ion-protein binding mechanistic insights have been well discussed using isothermal titration calorimetry (ITC). Overall, these experiments have reported that their interactions are pH-dependent and entropically driven. This research also reports the strongly hydrated metal ions as water structure breaker unlike osmolytes based on DSC studies. These experimental results have highlighted higher concentrations of different metal ions effect on the protein hydration and thermostability which might be helpful in understanding their interactions in aqueous solutions.

Deep learning based diagnosis of Alzheimer's disease using FDG-PET images.

PURPOSE: The aim of this study is to develop a deep neural network to diagnosis Alzheimer's disease and categorize the stages of the disease using FDG-PET scans. Fluorodeoxyglucose positron emission tomography (FDG-PET) is a highly effective diagnostic tool that accurately detects glucose metabolism in the brain of AD patients. MATERIAL AND METHODS: In this work, we have developed a deep neural network using FDG-PET to discriminate Alzheimer's disease subjects from stable mild cognitive impairment (sMCI), progressive mild cognitive impairment (pMCI), and cognitively normal (CN) cohorts. A total of 83 FDG-PET scans are collected from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database, including 21 subjects with CN, 21 subjects with sMCI, 21 subjects with pMCI, and 20 subjects with AD. RESULTS: The method has achieved remarkable accuracy rates of 99.31% for CN vs. AD, 99.88% for CN vs. MCI, 99.54% for AD vs. MCI, and 96.81% for pMCI vs. sMCI. Based on the experimental results. CONCLUSION: The results show that the proposed method has a significant generalisation ability as well as good performance in predicting the conversion of MCI to AD even in the absence of direct information. FDG-PET is a well-known biomarker for the identification of Alzheimer's disease using transfer learning.

Thermodynamics of modulation of interaction of α-helix inducer 2, 2, 2-trifluoroethanol with lysozyme in presence of cationic, anionic and non-ionic surfactants.

The interactions of anionic sodium dodecyl sulphate (SDS), cationic cetyltrimethylammonium bromide (CTAB) and nonionic triton X-100 (TX-100) surfactants with lysozyme at pH = 2.4 have been studied individually as well as in combination with 2,2,2-trifluoroetanol (TFE). Urea has also been used in combination with surfactants. By using these combinations, efforts have been made to obtain partially folded conformations of the protein in the presence of surfactants and effect of α-helix inducer 2,2,2-trifluoroethanol on these intermediate states. Thermodynamic analysis of all these interactions has been done employing a combination of UV-visible, fluorescence and circular dichroism spectroscopies. The results have been correlated with each other and characterized qualitatively as well as quantitatively. At lower concentration of surfactant, the thermodynamic parameters indicated the destabilizing effect of SDS, stabilizing effect of CTAB and unappreciable destabilizing impact of TX-100 on lysozyme. The enhancement in destabilization effect or reduction in stabilization effect of surfactants on lysozyme in the presence of TFE and urea has also been indicated.Communicated by Ramaswamy H. Sarma.

Mode of interaction of altretamine with calf thymus DNA: biophysical insights.

Insights into drug-DNA interactions have importance in medicinal chemistry as it has a major role in the evolution of new therapeutic drugs. Therefore, binding studies of small molecules with DNA are of significant interest. Spectroscopy, coupled with measurements of viscosity and molecular docking studies were employed to obtain mechanistic insights into the binding of altretamine with calf thymus DNA (CT-DNA). The UV-visible spectroscopic measurements study confirmed altretamine-CT-DNA complex formation with affinity constant ([15.68 ± 0.04] × 103 M-1), a value associated with groove binding phenomenon. The associated thermodynamic signatures suggest enthalpically driven interactions. The values of standard molar free energy change (ΔGmo) -(23.93 ± 0.23) kJ mol-1, enthalpy change (ΔvHHmo) -(50.84 ± 0.19) kJ mol-1 and entropy change (ΔSmo) -(90.29 ± 0.12) JK-1 mol-1 indicate the binding is thermodynamically favorable and an important role of the hydrogen bonds and Van der Waals interactions in the binding of altretamine with CT-DNA. Circular dichroism spectroscopy indicated insignificant conformational changes in the DNA backbone upon interaction with altretamine suggesting no distortion and/or unstacking of the base pairs in the DNA helix. UV-melting study suggested that the thermal stability of the DNA backbone is not affected by the binding of the drug. Competitive displacement assays with ethidium bromide, Hoechst-33258 and DAPI established the binding of altretamine with CT-DNA in the minor groove. The mode of binding was further confirmed by viscosity and molecular docking studies. Molecular docking further ascertained binding of altretamine in the minor groove of the CT-DNA, preferably with the A-T rich sequences.[Formula: see text]HighlightsAltretamine binds CT-DNA which is enthalpically driven with Ka of the order of 103Insignificant conformational change is observed due to DNA-altretamine complexationAltretamine binds favorably with A-T rich sequences in the minor groove of CT-DNAMechanistic insights obtained based on thermodynamic signaturesCommunicated by Ramaswamy H. Sarma.

Prevention of insulin fibrillation by biocompatible choline-amino acid based ionic liquids: Biophysical insights.

We have synthesized biocompatible ionic liquids (ILs) with choline as cation and amino acids as anions to explore their potential towards prevention of fibrillation in insulin and the obtain corresponding mechanistic insights. This has been achieved by examining the effect of these ILs on insulin at the nucleation, elongation and maturation stages of the fibrillation process. A combination of high sensitivity isothermal titration calorimetry (ITC) and differential scanning calorimetry (DSC) have been employed along with spectroscopy and microscopy to evaluate interaction of the ILs at each stage of fibrillation quantitatively. Choline glycinate is observed to provide maximum stabilization to insulin compared to that provided by choline prolinate, choline leucinate, and choline valinate. This increased thermal stabilization has direct correlation with the extent of reduction in the fibrillation of insulin by ILs determined using Thioflavin T and 8-anilinonaphthalene sulfonate based fluorescence assays. ITC has permitted understanding nature of interaction of the ILs with the protein at different fibrillation stages in terms of standard molar enthalpy of interaction whereas DSC has enabled understanding the extent of reduction in thermal stability of the protein at these stages. These ILs are able to completely inhibit formation of insulin aggregates at a concentration of 50 mM. Stabilization of proteins by ILs could be explained based on involvement of preferential hydration process. The work provides biocompatible IL based approach in achieving stability and prevention of fibrillation in insulin.

Mechanistic physicochemical insights into glycation and drug binding by serum albumin: Implications in diabetic conditions.

The drug binding ability of serum albumin might get affected as a result of its glycation under diabetic conditions. It requires not only an understanding of the effect of glycation of the protein upon association with the drug, but also calls for an assessment of structure-property-energetics relationships. A combination of ultrasensitive calorimetric, spectroscopic and chromatographic approach has been employed to correlate thermodynamic signatures with recognition, conformation and mechanistic details of the processes involved. An important observation from this work is that 3-(dansylamino) phenyl boronic acid (DnsPBA) assay cannot always determine the extent of glycation as evidenced by MALDI-TOF mass spectra of glycated HSA due to its selectivity for 1,2 or 1,3 cis-diol structures which may be absent in certain AGEs. Protein gets modified post glycation with the formation of advanced glycation end products (AGEs), which are monitored to be targeted by the guanidine group present in anti-diabetic drugs. AGEs formed in the third and fourth week of glycation are significant in the recognition of anti-diabetic drugs. The results with metformin and aminoguanidine suggest that the extent of binding depends upon the number of guanidine group(s) in the drug molecule. Open chain molecules having guanidine group(s) exhibit stronger affinity towards glycated HSA than closed ring entities like naphthalene or pyridine moiety. The observation that the drug binding ability of HSA is not adversely affected, rather strengthened upon glycation, has implications in diabetic conditions. A rigorous structure-property-energetics correlation based on thermodynamic signatures and identification of functional groups on drugs for recognition by HSA are essential in deriving guidelines for rational drug design addressing diabetes.

Potential of tetradecyltrimethylammonium bromide in preventing fibrillation/aggregation of lysozyme: biophysical studies.

A key step in the prevention of neurodegenerative disorders is to inhibit protein aggregation or fibrillation process. Functionality recognition is an essential strategy in developing effective therapeutics in addressing the treatment of amyloidosis. Here, we have focused on an approach based on structure-property energetics correlation associated with tetradecyltrimethylammonium bromide (TTAB), a cationic surfactant that acts as an inhibitor targeting different stages of hen egg-white lysozyme fibrillation. Characterization of amyloid fibrils and the inhibitory capability of 16 mM TTAB surfactant on fibrillation were investigated with the calorimetric, spectroscopic and microscopic techniques. ThT binding fluorescence studies inferred that micellar TTAB exerts its maximum inhibitory effect against amyloid fibrillation than monomer TTAB. The TEM measurements also confirmed complete absence of amyloid fibrils at micellar TTAB. At the same time, the transformation of ß-sheet to α-helix under the action of TTAB was confirmed by the Far-UV CD spectroscopy. Although there have been some reports suggesting that cationic surfactants can induce aggregation in proteins, this work suggests that polar interactions between head groups of TTAB and amyloid fibrils are the predominant factors that cause retardation in fibrillation by interrupting/disturbing the intermolecular hydrogen bond of ß-sheets. The present finding has explored the knowledge-based details in developing efficient potent inhibitors and provides a platform to treat diseases associated with protein misfolding.Communicated by Ramaswamy H. Sarma.

HSA nanoparticles in drug recognition: mechanistic insights with naproxen, diclofenac and methimazole.

Protein-based nanoparticles offer a suitable targeted delivery platform to drugs in terms of biocompatibility, biodegradability and abundance in nature. Physicochemical understanding of drug encapsulation by protein nanoparticles and their impact on protein aggregation is essential. In this work, we have examined quantitative aspects of encapsulation of non-steroidal anti-inflammatory drugs naproxen and diclofenac sodium, and anti-thyroid drug methimazole in nanoparticles of human serum albumin (HSA NPs) by using ultrasensitive calorimetry. Thermodynamic signatures accompanying the interactions revealed that the partitioning of all these drugs in HSA NPs is primarily driven via contributions from desolvation of highly hydrated nanoparticles surface. Furthermore, the effect of these nanoparticles on fibrillation of HSA has also been studied. HSA NPs are determined to be ineffective towards inhibition of fibrillation under employed conditions. However, the extent of inhibition by HSA NPs varies depending upon the structural characteristics of the drugs. Such studies help to gain mechanistic aspects on drug loading into protein-based nanoparticles and are expected to provide useful insights into improving existing nano-drug carriers and their efficiency in preventing protein fibrillation.Communicated by Ramaswamy H. Sarma.

Unusual human serum albumin fibrillation inhibition by ketoprofen and fenoprofen: Mechanistic insights.

Development of efficient therapeutic strategies to combat protein misfolding and fibrillation is of great clinical significance. In the current study, efforts have been made to obtain qualitative and quantitative insights into interactions of anti-inflammatory drugs; ketoprofen and fenoprofen with the transport protein HSA and their inhibitory action on fibrillation by employing a combination of calorimetric, spectroscopic, microscopic, and molecular docking methods. Interestingly, both ketoprofen and fenoprofen are able to completely inhibit fibrillation of HSA when added at a concentration of 0.5 mM for fenoprofen or 1 mM ketoprofen. Further, no amorphous aggregates are formed. Isothermal titration calorimetric studies highlight the predominant role of polar interactions of these drugs with protein in prevention of fibrillation. The role of conformational flexibility of benzoyl and phenoxy groups of drugs has been correlated with inhibition efficiency. Such studies highlight the role of functionality required for an inhibitor in addressing neurodegenerative diseases.

Correlating the Properties of Antibiotics with the Energetics of Partitioning in Colloidal Self-Assemblies and the Effect on the Binding of a Released Drug with a Target Protein.

The bioavailability of drugs and the monitoring of efficient dosage requires drug delivery through suitable vehicles. The partitioning characteristics of the drugs in the delivery vehicles is determined by their molecular features and structure. A quantitative understanding of the partitioning of drugs into delivery media and its subsequent release and binding to the target protein is essential to deriving guidelines for rational drug design. We have studied the partitioning of aminoglycosides and macrolide antibiotic drugs kanamycin, gentamicin, azithromycin, and erythromycin in cationic, nonionic, and the mixture of cationic and nonionic self-assemblies. The quantitative aspects of drug partitioning followed by the monitoring of its interaction with target model protein bovine serum albumin on subsequent release have been performed by using a combination of spectroscopy and high-sensitivity calorimetry. The mechanisms of partitioning have been analyzed on the basis of the values of standard molar enthalpy, entropy, the Gibbs free-energy change, and stoichiometry of interaction. The integrity of the binding sites and the effects of the components of the self-assemblies and the released drug on the serum albumin were analyzed by using differential scanning calorimetry and circular dichroism spectroscopy. The thermodynamic signatures of drug partitioning and subsequent binding to target protein have enabled an in-depth correlation of the structure-property-energetics relationships which are crucial for the broader objective of rational drug design.

Self-assemblies of pluronic micelles in partitioning of anticancer drugs and effectiveness of this system towards target protein.

Micelles formed by pluronic triblock copolymers are known to be a promising class of drug delivery vehicles. Quantitative mechanistic insights into the ability of pluronic micelles to improve the solubility of poorly water soluble drugs, encapsulation and delivery of hydrophilic drugs are not available. The current study evaluated the energetics of encapsulation of chemotherapeutic drugs gemcitabine, cytarabine, and hydroxyurea in pluronic F127 and F68 micelles. In addition, the interactions of the drugs released from pluronic micellar media with serum albumin, which is a major circulatory transport protein, and subsequent conformational changes have also been analyzed with the help of calorimetry and spectroscopy. All the drugs showed improved partitioning in F127 micelles, the extent of which slightly increased with temperature rise. Interestingly, drug-protein binding is enhanced upon delivery from pluronic micelles without affecting the conformational integrity of the protein. This study highlights the role of drug functionalities, hydrophobicity, and steric factors towards their partitioning in pluronic micelles. Such studies are important in understanding physicochemical aspects of drug encapsulation and release, and lead to establishing structure-property-energetics correlations for developing suitable nano-drug delivery vehicles.

Mechanistic insights into encapsulation and release of drugs in colloidal niosomal systems: biophysical aspects.

Vesicular systems such as niosomes provide an alternative to improve drug delivery systems. The efficiency of a drug delivery vehicle is strongly dependent on its components which decide its interaction with partitioned drug(s) and locus of site of partitioning. A quantitative understanding of the physical chemistry underlying partitioning of drugs in complex systems of self-assemblies such as niosomes is scarcely available. In order to obtain quantitative mechanistic insights into partitioning and release of drugs [mitoxantrone (MTX) and ketoprofen (KTP)] in systems of niosomes, we have employed ultrasensitive calorimetry, spectroscopy and microscopy to establish correlations between functionality and energetics which could provide guidance towards rational drug design and choice of suitable non-ionic surfactant-based drug delivery vehicles. Electron microscopy and dynamic light scattering (DLS) methods were used for characterization and assessing the morphology of niosomes. We present here a calorimetry-based approach in assessing the partitioning of the anticancer drugs mitoxantrone and ketoprofen in niosomes and their release to human serum albumin (HSA) employing isothermal titration calorimetry (ITC), differential scanning calorimetry (DSC) and comparison with equilibrium dialysis. The thermodynamic signatures and kinetics of release were analyzed to obtain insights into the role of the functional groups on the drugs in the partitioning process. The assessment of thermal and conformational stability of proteins during drug binding and the effect of drug delivery vehicles on proteins is also crucial. To assess these effects, DSC studies on HSA in the presence and absence of drugs and niosomes were also performed. Finally, the efficacy of the system to impact the cell viability of the MDA-MB-231 triple-negative breast carcinoma cell line was analysed using MTT assay.

Unraveling diverse action of triton X-100 and methimazole on lysozyme fibrillation/aggregation: Physicochemical insights.

Identification of functionalities responsible for prevention of fibrillation in proteins is important to design effective drugs in addressing neurodegenerative diseases. We have used nonionic surfactant triton X-100 (TX-100) and antithyroid drug methimazole (MMI) to understand mechanistic aspects of action of these molecules having different functionalities on hen egg-white lysozyme at different stages of fibrillation. After establishing the nucleation, elongation and maturation stages of fibrillation of protein at 57 °C, energetics of interactions with these molecules have been determined by using isothermal titration calorimetry. Differential scanning calorimetry has permitted assessment of thermal stability of the protein at these stages, with or without these molecular entities. The enthalpies of interaction of TX-100 and MMI with protein fibrils suggest importance of hydrogen bonding and polar interactions in their effectiveness towards prevention of fibrils. TX-100, in spite of several polar centres, is unable to prevent fibrillation, rather it promotes. MMI is able to establish polar interactions with interacting strands of the protein and disintegrate fibrils. A rigorous comparison with inhibitors reported in literature highlights importance -OH and >CO functionalities in fibrillation prevention. Even though MMI has hydrogen bonding centres, its efficiency as inhibitor falls after the inhibited lysozyme fibrils further interact and form amorphous aggregates.

Physicochemical Insights into the Role of Drug Functionality in Fibrillation Inhibition of Bovine Serum Albumin.

To revert amyloid fibrils to their native state is a challenge in finding a solution to prevent neurodegenerative diseases. We have adopted a structure-property-energetics correlation-based approach with drugs (5-fluorouracil and hydroxyurea) having multiple hydrogen-bond donors and acceptors as inhibitors targeting different stages of bovine serum albumin fibrillation. We present here a quantitative comprehensive biophysical approach for identifying functionalities in molecules, which offers this feature in terms of polarity and hydrogen bonding. Our objective of identifying the functionality on a drug molecule that establishes effective intermolecular hydrogen bonding with ß-strands of protein fibrils was achieved by combined calorimetric, spectroscopic, volumetric, and microscopic correlations. Relationships have been established among thermodynamic signatures, F19-NMR chemical shifts, hydrodynamic diameters, and thermal expansion coefficients to demonstrate that the open-chain molecule is a better inhibitor of fibrillation, but its efficiency decreases with the formation of amorphous aggregates, as compared to the molecule having a uracil ring. The results have provided quantitative insights into the role of polarity and hydrogen bonding in prevention of the fibrillation process. The approach adopted here highlights the physical chemistry underlying such biologically important processes and hence has significance in deriving guidelines for rational drug design.

Partitioning of anticancer drug 5-fluorouracil in micellar media explored by physicochemical properties and energetics of interactions: Quantitative insights for implications in drug delivery.

Drug delivery vehicles such as micelles, vesicles and other nanoemulsions are necessary for enhanced bioavailability of drugs in the body. We have measured and correlated physicochemical properties of an anticancer drug 5-fluorouracil in the micelles of anionic surfactant sodium dodecyl sulfate. cationic surfactant hexadecyltrimethylammonium bromide, and non-ionic surfactant triton X-100 with the energetics of interactions. Thermodynamic signatures accompanying the partitioning of drug into surfactant micelles along with standard partial molar volume and standard partial molar compressibilities of transfer from water to the micelles have been interpreted in terms of strength, nature and extent of partitioning. Functional groups on the drug responsible for interaction/partitioning in micelles have been identified. Interaction of 5-fluorouracil in two or three sequential partitioning behavior depending on the nature of the surfactant micelles has enabled detailed mechanistic analysis of the partitioning process. Structure-property-energetics relationship to obtain deeper insights into the nature of interaction between the drug and micelles has been addressed. Such studies provide information on the significance of functional groups on the drug molecule which can be modified for optimum partitioning in drug delivery vehicles to account for effective target oriented release.

Anticancer altretamine recognition by bovine serum albumin and its role as inhibitor of fibril formation: Biophysical insights.

Binding of anticancer drug altretamine with bovine serum albumin (BSA) and its inhibitory effect on fibrillation of the protein has been studied by using a combination of spectroscopic and calorimetric methods. Altretamine is observed to bind with BSA with a moderate binding affinity of the order of 105, which is weakly temperature dependent. Circular dichroism, fluorescence spectroscopic and dynamic light scattering methods have been employed to monitor the conformational change in the protein. Time correlated single photon counting measurements have confirmed ground state complexation of the drug with the protein. Docking studies have led to identification of binding sites on BSA at site III in domain IB. Thioflavin T (ThT) fluorescence emission has been used as a tool to monitor the formation of fibrils/aggregates in BSA. It is observed that anticancer drug altretamine can also act as an inhibitor of fibrillation in BSA and hence can be useful in the treatment of neuro-degenerative diseases. Differential scanning calorimetry has been employed to study the thermal transitions of BSA at different stages of the fibrillation process with and without altretamine to obtain insights into the extent of stabilisation provided by the drug to the protein in native, nucleation/elongation and matured state in the fibrillation process.

A look back at the molten globule state of proteins: thermodynamic aspects.

Interest in protein folding intermediates lies in their significance to protein folding pathways. The molten globule (MG) state is one such intermediate lying on the kinetic (and sometimes thermodynamic) pathway between native and unfolded states. Development of our qualitative and quantitative understanding of the MG state can provide deeper insight into the folding pathways and hence potentially facilitate solution of the protein folding problem. An extensive look at literature suggests that most studies into protein MG states have been largely qualitative. Attempts to obtain quantitative insights into MG states have involved application of high-sensitivity calorimetry (differential scanning calorimetry and isothermal titration calorimetry). This review addresses the progress made in this direction by discussing the knowledge gained to date, along with the future promise of calorimetry, in providing quantitative information on the structural features of MG states. Particular attention is paid to the question of whether such states share common structural features or not. The difference in the nature of the transition from the MG state to the unfolded state, in terms of cooperativity, has also been addressed and discussed.