interaction of drugs with serum albumin, the most abundant protein in plasma, has a great significance in pharmaceutical sciences. it can affect the biological activity, toxicity, and pharmacokinetics of drugs and design of dosages. determination of the impact of chemical modifications of albumin and its structural changes upon interaction with drugs are very important when drugs bind with albu...

Hybrid-density functional theory (B3LYP/Def2-TZVPP) based method and NBOinterpretation were used to investigate the conformational behavior of 1,2-dihalodisilanes[halo=F (1), Cl (2), Br (3), I (4)]. The B3LYP/Def2-TZVPP results showed that the anticonformations of compounds 1-4 are more stable than their corresponding gaucheconformations. The stability of the anti conformation compared to the g...

Phycocyanobilin (PCB) binds with high affinity (2.2 x 106 M-1 at 25°C) to human serum albumin (HSA) at sites located in IB and IIA subdomains. The aim of this study was to examine effects of PCB binding on protein conformation and stability. Using 300 ns molecular dynamics (MD) simulations, UV-VIS spectrophotometry, CD, FT-IR, spectrofluorimetry, thermal denaturation and susceptibility to tryps...

The pK values of the histidine residues in ribonuclease T1 (RNase T1) are unusually high: 7.8 (His-92), 7.9 (His-40), and 7.3 (His-27) [Inagaki et al. (1981) J. Biochem. 89, 1185-1195]. In the RNase T1 mutant Glu-58----Ala, the first two pK values are reduced to 7.4 (His-92) and 7.1 (His-40). These lower pKs were expected since His-92 (5.5 A) and His-40 (3.7 A) are in close proximity to Glu-58 ...

Residue His119 acts as an acid/base during the cleavage/hydrolysis reactions catalyzed by bovine pancreatic ribonuclease A (RNase A). In the native enzyme, His119 forms a hydrogen bond with Asp121. This His...Asp dyad is conserved in all homologous pancreatic ribonucleases of known sequence. Yet, replacing Asp121 with an asparagine or alanine residue does not have a substantial effect on either...

The pH-induced conformational transition in the CuA domain of subunit II of cytochrome oxidase of Paracoccus denitrificans (PdII) has been investigated using various spectroscopic and stopped-flow kinetic methods. UV-visible absorption and circular dichroism studies showed that an increase in pH from 6 to 10 leads to a conformation change with pK(a) = 8.2 associated with the CuA site of the pro...

Unnatural amino acid mutagenesis, in combination with molecular modeling and simulation techniques, was used to probe the effect of side chain structure on protein stability. Specific replacements at position 133 in T4 lysozyme included (i) leucine (wt), norvaline, ethylglycine, and alanine to measure the cost of stepwise removal of methyl groups from the hydrophobic core, (ii) norvaline and O-...

α-Helices are the most frequently occurring elements of the secondary structure in water-soluble globular proteins. Their increased conformational stability is among the main reasons for the high thermal stability of proteins in thermophilic bacteria. In addition, α-helices are often involved in protein interactions with other proteins, nucleic acids, and the lipids of cell membranes. That is w...

In this study techniques based on measurement of intrinsic tryptophan (Trp) fluorescence were used to monitor the stability and conformational flexibility of the single tryptophan protein monellin which was entrapped in sol–gel derived glass monoliths formed from tetraethylorthosilicate. The monoliths were aged either in buffer (wet-aged) or in air (dry-aged). The steady-state fluorescence spec...