The adsorption of cytochrome c onto a range of different mesoporous silicates (MPS) was studied. The materials used, templated using both cationic and nonionic surfactants, have average pore-size diameters in the range from 28 to 130 A. Cytochrome c was found to bind to all MPS investigated, with the pore diameter of the material, which was measured by N2 gas adsorption, being crucial to mesopore penetration. The adsorption of a range of proteins with isoelectric points between 1 and 10 was investigated. For adsorption to occur, the surface charges of the protein and of the MPS must be complementary, in addition to the requirement that the pore diameter be sufficiently large. Pepsin at pH 6.5, for example, is negatively charged and does not adsorb onto cyano-modified silicate whereas subtilisin, which is of a similar size and bears an overall positive charge, is adsorbed. Using resonance Raman spectroscopy, cytochrome c was observed to occur in both high spin and low spin states, in contrast to that in solution, where the protein is predominantly in the low spin state. The presence of the high spin state may account for the enhanced peroxidative activity of the adsorbed protein.

Mechanistic and Structural Features of Protein Adsorption onto Mesoporous Silicates

Recent studies have shown that various synthetic as well as therapeutically active naturally occurring flavonols possess novel luminescence properties that can potentially serve as highly sensitive monitors of their microenvironments in biologically relevant systems. We report a study on the interactions of bovine serum albumin (BSA) with the model flavonol 3-hydroxyflavone (3HF), using the excited-state proton-transfer (ESPT) luminescence of 3HF as a probe. Upon addition of BSA to the flavonoid solutions, we observe remarkable changes in the absorption, ESPT fluorescence emission and excitation profiles as well as anisotropy (r) values. Complexation of 3HF with protein results in a pronounced shift (20 nm) of the ESPT emission maximum of the probe (from lambda(max)(em) = 513 nm to lambda(max)(em) = 533 nm) accompanied by a significant increase in fluorescence intensity. The spectral data also suggest that, in addition to ESPT, the protein environment induces proton abstraction from 3HF leading to formation of anionic species in the ground state. Fairly high values of anisotropy are observed in the presence of BSA for the tautomer (r = 0.25) as well as anion (r = 0.35) species of 3HF, implying that both the species are located in motion-restricted environments of BSA molecules. Analysis of relevant spectroscopic data leads to the conclusions that two binding sites are involved in BSA-3HF interaction, and the interaction is slightly positively cooperative in nature with a similar binding constant of 1.1 - 1.3 x 10(5) M(-1) for both these sites. Proteins 2001;43:75-81.

Protein-flavonol interaction: fluorescence spectroscopic study.

Alginate coated chitosan core-shell nanoparticles for efficient oral delivery of naringenin in diabetic animals-An in vitro and in vivo approach.

Betulinic acid (BA) has anti cancer and anti-HIV activity and has been proved to be therapeutically effective against cancerous and HIV-infected cells. Human serum albumin (HSA) is the predominant protein in the blood. Most drugs that bind to HSA will be transported to other parts of the body. Using micro TOF-Q mass spectrometry, we have shown, for the first time that BA isolated from a plant (Tephrosia calophylla) binds to HSA. The binding constant of BA to HSA was calculated from fluorescence data and found to be KBA = 1.685 ± 0.01 × 106 M−1, indicating a strong binding affinity. The secondary structure of the HSA–BA complex was determined by circular dichroism. The results indicate that the HSA in this complex is partially unfolded. Further, binding of BA at nanomolar concentrations of BA to free HSA was detected using micro TOF-Q mass spectrometry. The study revealed a mass increase from 65199 Da (free HSA) to 65643 Da (HSA + drug), where the additional mass of 444 Da was due to bound BA. Based on the results of this study, it is suggested that micro TOF-Q mass spectrometry is useful technique for drug binding studies.

Betulinic acid binding to human serum albumin: A study of protein conformation and binding affinity

Effect of nonenzymatic glycation on functional and structural properties of hemoglobin.

Interaction of chlorpromazine with myoglobin and hemoglobin: A comparative study

Structural organisations of hemoglobin and myoglobin influence their binding behaviour with phenothiazines

The extent of oxygen release from two heme proteins, haemoglobin and myoglobin have been studied in the presence of trifluoperazine and chlorpromazine (5–1000 μM).



At a molar ratio (drug: protein) of 1.5, the release of oxygen from haemoglobin was 4 and 15% in the presence of chlorpromazine and trifluoperazine respectively, while from myoglobin the corresponding values were 20 and 40%.



The findings were attributed to the greater extent of local conformational change around tryptophan moieties of each of the proteins induced by trifluoperazine.

Jaya Bhattacharyya

Papers

Interaction of chlorpromazine with myoglobin and hemoglobin: A comparative study

Structural organisations of hemoglobin and myoglobin influence their binding behaviour with phenothiazines

Trifluoperazine is more effective than chlorpromazine in releasing oxygen from haemoglobin and myoglobin.