Protein disulfide isomerase (PDI) catalyzes the rearrangement of nonnative disulfide bonds in the endoplasmic reticulum of eukaryotic cells, a process that often limits the rate at which polypeptide chains fold into a native protein conformation. The mechanism of the reaction catalyzed by PDI is unclear. In assays involving protein substrates, the reaction appears to involve the complete reduct...

Isomerization of glucose to fructose is a key reaction step in the efficient production valuable renewable chemical intermediates from biomass. Zeolites have been widely used promote isomerization, but only limited structure-activity relationship has established and applied optimize reaction. In this work, commercial Y zeolites were modified by alkaline-treatment their physicochemical propertie...

Post-translational modifications that do not result in a change in mass are particularly difficult to detect by mass spectrometry. For example, isomerization of aspartic acid or epimerization of any chiral residue within a peptide do not lead to mass shifts but can be identified by examination of independently acquired tandem mass spectra or by combination with another technique. For analysis o...

A new class of dendrons and dendrimers containing azobenzene units (bearing up to 29 azobenzene groups for four generations) were designed and synthesized with the convergent method, which uses azobenzene derivatives as monomers and benzyl ester groups as linkages leading to photoresponsive dendrons and dendrimers with azobenzene units throughout their architecture. Photochemical isomerization ...

Thermally induced gauche–trans isomerization and direct solute–solvent interactions of the solute, ethyl isocyanate ~EIC!, in the solvent, 2-methylpentane ~2MP!, are investigated using ultrafast infrared vibrational echo experiments and linear vibrational absorption spectroscopy of the isocyanate ~N5C5O! antisymmetric stretching mode ~2278 cm!. Both the EIC vibrational echo measured pure vibrat...

Photoisomerization of 11-cis-retinal to all-trans-retinal triggers phototransduction in the retinal photoreceptor cells and causes ultimately the sensation of vision. 11-cis-Retinal is enzymatically regenerated through a complex set of reactions in adjacent retinal pigment epithelial cells (RPE). In this study using all-trans-9-desmethylretinol (lacking the C(19) methyl group) and all-trans-13-...

The recovery reaction of the signaling state of photoactive yellow protein includes the following: (i) deprotonation of the p-coumaryl chromophore, (ii) refolding of the protein, and (iii) chromophore re-isomerization from the cis to the trans configuration. Through analysis of the pH dependence of this recovery reaction, we were able to provide proof for the existence of an additional photocyc...

Photoinduced conformational isomerization of formic acid has been studied in a low-temperature argon matrix. It is found that conformational isomerization occurs when the photon energy is below the energy barrier for this process. The quantum yield for the process near the top of the barrier is comparable with the quantum yield above the barrier and drops at lower energies. The isomerization ta...

The mono-metallic and bi-metallic catalysts have been prepared by impregnating with solutions containing a compound of H2PtCl6,WO3 and 1ml HCl (0.1 mol). It should be noted that the catalysts’ activity and selectivity have been determined under these conditions : 450-5000C ,and 15-25atm by H2. For converting n-heptane , the molar ratio H2/C7H16 is 5 , and LHSV is 1.5ml/h. It has been proved tha...

In unfolded RNase A there is an interconversion between slow-folding and fast-folding forms (U(S) right harpoon over left harpoon U(F)) that is known to show properties characteristic of proline isomerization in model peptides. Here, we accept the evidence that U(S) molecules contain nonnative proline isomers and we ask about the isomerization of these proline residues during folding. The U(S) ...