Further studies on associations between leprosy and genetic markers in human serum

Summary Seven serum proteins were typed on a sample of 910 individuals from Angola, Africa. The sample consisted of both leprosy patients and healthy controls from the same geographical area. Significant associations with leprosy were found for the Hp and Pi systems. The results are discussed.

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Zusammenfassung An einer Stichprobe von 910 Individuen aus Angola (Afrika) wurden sieben Serumprotein-Systeme untersucht. Diese Stichprobe umfaßt Leprakranke und gesunde Kontrollen aus dem gleichen geographischen Raum. Signifikante Assoziationen wurden nur zwischen Lepra und den Systemen Haptoglobin und Pi gefunden. Die Ergebnisse werden im einzelnen diskutiert.

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Supported by the Deutsche Forschungsgemeinschaft.     

Spectroscopic studies of the interaction between hypocrellin B and human serum albumin

Previous work has proved that hypocrellin B (HB) binds to human serum albumin (HSA) at a specific site instead of distributed randomly on the surface of a protein. In the current work, further investigation by using bilirubin as a site I marker indicates that HB can compete for the same site with bilirubin, suggesting that the HB binding site is located at sub-domain IIA (site I) of HSA. Moreover, bound to HSA, the HB fluorescence was found to be pH sensitive in physiological range (pH 6.0-8.0). The increasing of binding constant of HB to HSA in the pH range 6-8 also indicates that the N<-->B transition modulates the microenvironment changes of the binding site and influences considerably the binding between HB and HSA. Furthermore, picosecond time-resolved fluorescence spectra of HB-HSA complex in PBS indicate an additional short-lived component compared to that for HB in benzene, which may be assigned to the process of electron transfer from Trp-214 to HB.     

Further studies on the resolution of human mercapt- and nonmercaptalbumin and on human serum albumin in the elderly by high-performance liquid chromatography

High-performance liquid chromatographic (HPLC) analysis of human serum albumin (HSA) on Asahipak GS-520 showed at least two peaks, the principal component corresponding to human mercaptalbumin (HMA) and the secondary one to nonmercaptalbumin (HNA). HPLC analysis of HSA on Asahipak ES-520 N showed three peaks, the principal component corresponding to HMA, the secondary one to HNA having mixed disulfide with cysteine or glutathione and the tertiary one to HNA oxidized higher than mixed disulfide. Two kinds of rapid HPLC for the resolution of HSA into HMA and HNA were developed by the present authors. Using these HPLC, the present authors found a significant decrease in the fraction of HMA in the elderly.     

The interaction between cholesterol and human serum albumin

The interaction between cholesterol and Human Serum Albumin (HSA) was studied by fluorescence technique. Addition of cholesterol causes decreasing of the fluorescence intensity of HSA and the mechanism can be attributed to static quenching. Both negative enthalpy and entropy change indicate this binding was an "enthalpy-driven" reaction. The number of binding site and distance between residues and ligands were also calculated: n = 0.98, r = 3.84 nm. UV-vis spectra showed HSA molecules unfolded to some extent and the hydrophobicity was decreased in the presence of cholesterol.     

Interactions between antimalarial indolone-N-oxide derivatives and human serum albumin

The binding affinity of human serum albumin (HSA) to three antimalarial indolone-N-oxide derivatives, INODs, was investigated under simulated physiological conditions using fluorescence spectroscopy in combination with UV-vis absorption and circular dichroism (CD) spectroscopy. Analysis of fluorescence quenching data of HSA by these compounds at different temperatures using Stern-Volmer and Lineweaver-Burk methods revealed the formation of a ground state indolone-HSA complex with binding affinities of the order 10(4) M(-1). The thermodynamic parameters ΔG, ΔH, and ΔS, calculated at different temperatures, indicated that the binding reaction was endothermic and hydrophobic interactions play a major role in this association. The conformational changes of HSA were investigated qualitatively using synchronous fluorescence and quantitatively using CD. Site marker competitive experiments showed that the binding process took place primarily at site I (subdomain IIA) of HSA. The number of binding sites and the apparent binding constants were also studied in the presence of different ions.     

Studies on the interaction between Ag(+) and human serum albumin

The interaction between Ag(+) and human serum albumin (HSA) has been intensively studied by means of equilibrium dialysis, ligand-to-metal charge transition (LMCT) bands, circular dichroism (CD) and Raman spectroscopy. Scatchard analysis of the results of equilibrium dialysis indicates the presence of two types of binding sites for Ag(+) on HSA, and the orders of magnitude of binding stability constants are found to be 10(5) and 10(4), respectively. During the binding process, a gradual increase in absorbance values of LMCT bands is observed with time-scanning UV absorption spectra, implying the Ag(I) centers are continually formed in HSA. The time-scanning CD spectra provide evidence that the binding of Ag(+) induces HSA to undergo a slow rearrangement of tertiary structure, and to change from the original conformation in the absence of Ag(+) (B-state) to conformation binding with Ag(+) (A-state). The rate constants and activation free energy of A-B transition are calculated. The Raman spectrum of Ag(I)-HSA system shows distinct vibration bands at 224 and 246 cm(-1) in the low-frequency region, which significantly reveal the formation of Ag-S and Ag-N bonds. In addition, the electrostatic interaction between Ag(+) and negatively charged oxygen is also detected with Raman spectroscopy.     

Structure of human serum cholinesterase

Human cholinesterase has recently been sequenced and cloned. It is a glycoprotein of 4 identical subunits, each subunit containing 9 carbohydrate chains and 3.5 disulfide bonds. Protein folding is likely to be very similar in human cholinesterase and Torpedo acetylcholinesterase. The cholinesterases have no significant sequence homology with the serine proteases and seem to belong to a separate serine esterase family.     

Experimental and computational studies on the binding of diazinon to human serum albumin

In the present research, the binding properties of diazinon (DZN), as an organophosphorus herbicide, to human serum albumin (HSA) were investigated using combination of spectroscopic, electrochemistry, and molecular modeling techniques. Changes in the UV–Vis and FT-IR spectra were observed upon ligand binding along with a significant degree of tryptophan fluorescence quenching on complex formation. The obtained results from spectroscopic and electrochemistry experiments along with the computational studies suggest that DZN binds to residues located in subdomains IIA of HSA with binding constant about 1410.9 M^?1 at 300 K. From the thermodynamic parameters calculated according to the van’t Hoff equation, the enthalpy change ΔH° and entropy change ΔS° were found to be ?16.695 and 0.116 KJ/mol K, respectively. The primary binding pattern is determined by hydrophobic interaction and hydrogen binding occurring in so-called site I of HSA. DZN could slightly alter the secondary structure of HSA. All of experimental results are supported by computational techniques such as docking and molecular dynamics simulation using a HSA crystal model.     

Spectroscopic studies of interaction between CuO nanoparticles and bovine serum albumin

Recently, the great interests in manufacturing and application of metal oxide nanoparticles in commercial and industrial products have led to focus on the potential impact of these particles on biomacromolecules. In the present study, the interaction of copper oxide (CuO) nanoparticles with bovine serum albumin (BSA) was studied by spectroscopic techniques. The zeta potential value for BSA and CuO nanoparticles with average diameter of around 50 nm at concentration of 10 μM in the deionized (DI) water were ?5.8 and ?22.5 mV, respectively. Circular dichroism studies did not show any changes in the content of secondary structure of the protein after CuO nanoparticles interaction. Fluorescence data revealed that the fluorescence quenching of BSA by CuO nanoparticles was the result of the formed complex of CuO nanoparticles – BSA. Binding constants and other thermodynamic parameters were determined at three different temperatures. The hydrogen bond interactions are the predominant intermolecular forces to stabilize the CuO nanoparticle – BSA complex. This study provides important insight into the interaction of CuO nanoparticles with proteins, which may be of importance for further application of these nanoparticles in biomedical applications.