Chiral recognition of metalaxyl enantiomers by human serum albumin: evidence from molecular modeling and photophysical approach.

Metalaxyl is an acylamine fungicide, belonging to the most widely known member of the amide group. This task is aimed to scrutinize binding region and spatial structural change of principal vector human serum albumin (HSA) complex with (R)-/(S)-metalaxyl by exploiting molecular modeling, steady-state and time-resolved fluorescence, and circular dichroism (CD) approaches. According to molecular modeling, (R)-metalaxyl is situated within subdomains IIA and IIIA and the affinity of site I with (R)-metalaxyl is greater than site II, whereas (S)-metalaxyl is only located at subdomain IIA and the affinity of (S)-metalaxyl with site I is superior compared with that with (R)-metalaxyl. This coincides with the competitive ligand binding, guanidine hydrochloride-induced unfolding of protein, and hydrophobic 8-anilino-1-naphthalenesulfonic acid experiments; the acting forces between (R)-/(S)-metalaxyl and HSA are hydrophobic, π-π interactions, and hydrogen bonds, as derived from molecular modeling. Fluorescence emission manifested that the complex of (R)-/(S)-metalaxyl to HSA is the formation of adduct with an affinity of 10(4) M(-1), which corroborates the time-resolved fluorescence that the static type was operated. Furthermore, the changes of far-UV CD spectra evidence the polypeptide chain of HSA partially unfolded after conjugation with (R)-/(S)-metalaxyl. Through this work, we envisage that it can offer central clues on the biodistribution, absorption, and bioaccumulation of (R)-/(S)-metalaxyl.

Human serum albumin stability and toxicity of anthraquinone dye alizarin complexone: an albumin-dye model.

The complexation between the primary vector of ligands in blood plasma, human serum albumin (HSA) and a toxic anthraquinone dye alizarin complexone, was unmasked by means of circular dichroism (CD), molecular modeling, steady state and time-resolved fluorescence, and UV/vis absorption measurements. The structural investigation of the complexed HSA through far-UV CD, three-dimensional and synchronous fluorescence shown the polypeptide chain of HSA partially destabilizing with a reduction of α-helix upon conjugation. From molecular modeling and competitive ligand binding results, Sudlow's site I, which was the same as that of warfarin-azapropazone site, was appointed to retain high-affinity for alizarin complexone. Moreover, steady state fluorescence displayed that static type and Förster energy transfer is the operational mechanism for the vanish in the tryptophan (Trp)-214 fluorescence, this corroborates time-resolved fluorescence that HSA-alizarin complexone adduct formation has an affinity of 10(5) M(-1), and the driving forces were found to be chiefly π-π, hydrophobic, and hydrogen bonds, associated with an exothermic free energy change. These data should be utilized to illustrate the mechanism by which the toxicological action of anthraquinone dyes is mitigated by transporter HSA.

Potential toxicity and affinity of triphenylmethane dye malachite green to lysozyme.

Malachite green is a triphenylmethane dye that is used extensively in many industrial and aquacultural processes, generating environmental concerns and health problems to human being. In this contribution, the complexation between lysozyme and malachite green was verified by means of computer-aided molecular modeling, steady state and time-resolved fluorescence, and circular dichroism (CD) approaches. The precise binding patch of malachite green in lysozyme has been identified from molecular modeling and ANS displacement, Trp-62, Trp-63, and Trp-108 residues of lysozyme were earmarked to possess high-affinity for this dye, the principal forces in the lysozyme-malachite green adduct are hydrophobic and π-π interactions. Steady state fluorescence proclaimed the complex of malachite green with lysozyme yields quenching through static type, which substantiates time-resolved fluorescence measurements that lysozyme-malachite green conjugation formation has an affinity of 10(3)M(-1). Moreover, via molecular modeling and also CD data, we can safely arrive at a conclusion that the polypeptide chain of lysozyme partially destabilized upon complexation with malachite green. The data emerged here will help to further understand the toxicological action of malachite green in human body.

Features of the complex of food additive hesperidin to hemoglobin.

The purpose of the current work was to examine the complexation of a mammalian protein, hemoglobin (Hb) with a food additive hesperidin at physiological conditions. Molecular modeling, fluorescence, and circular dichroism (CD) methods were exploited to analyze the binding domain, affinity, and the effects of hesperidin conjugation on Hb spatial structure. From molecular modeling, central cavity of Hb was assigned to retain high-affinity for hesperidin, this corroborates the steady state fluorescence and hydrophobic ANS probe results. The association of hesperidin with Hb emerges fluorescence quenching via static type, this phenomenon display that the ground state complex formation with an affinity of 10(4)M(-1), and hypsochromic effect transpires. Additionally, the alterations of synchronous fluorescence, CD, and three-dimensional fluorescence suggest that the polypeptide chain of Hb partially folding after conjugation with hesperidin. The above data suggest that Hb plays a significant role in the plasma distribution and transportation of hesperidin and related dietary flavonoids.

A cyanopropyl reversed phase chromatography enables resolution of huperzine A and B on analytical and preparative scales.

Huperzine A (HupA) and huperzine B (HupB) are two medically important components of Huperzia serrata. It is difficult to obtain high yields of the separation from the plant using conventional liquid extraction and chromatography. However, this study has found that RP chromatography with cyanopropyl (CN) medium was able to separate these two analogs simultaneously from the plant extract with higher resolution. Comparison between a CN medium and a popular C18 medium demonstrated the superiority of the CN over the C18 in resolution for both analytical and preparative separation of HupA and HupB. A preparative process was developed for simultaneous purification of HupA and HupB from H. serrata. The yields on the basis of the mass of the herbal powder for HupA and HupB were 0.019 and 0.008% respectively, which were about 1.9 and 10 times of those reported in the literature.