RP-HPLC and spectroscopic characterization of Suwannee River water NOM after concentrated urea treatment and dialysis

International audienceSuwannee River natural organic matter (SRNOM) was treated by 7 M urea and then purified by dialysis on 10 kDa membrane. The untreated SRNOM and treated (USRNOM) samples were examined using UV–visible and fluorescence spectroscopies and reversed-phase high-performance liquid chromatography (RP-HPLC) with online absorbance and fluorescence detection. USRNOM was 1.5-fold more absorbing at 280 nm than SRNOM and four fold less fluorescent than SRNOM upon excitation at 270 nm. RP-HPLC analyses of the two samples revealed that USRNOM was somewhat more hydrophobic than SRNOM and both samples contained at least two groups of HS-like fluorophores with different hydrophobicity and protein-like fluorophore(s). Data indicate that protein-like fluorophores were not lost during dialysis. They showed hydrophobic properties and seemed highly fluorescent. HS-like and protein-like fluorophores from water NOM could be successfully separated by RP-HPLC. This raises the prospect of their further research and identification and could be significant for future NOM chemical structure characterization

Relationship between Changes in the Protein Folding Pathway and the Process of Amyloid Formation: The Case of Bovine Carbonic Anhydrase II

Many proteins form amyloid fibrils only under conditions when the probability of transition from a native (structured, densely packed) to an intermediate (labile, destabilized) state is increased. It implies the assumption that some structural intermediates are more convenient for amyloid formation than the others. Hence, if a mutation affects the protein folding pathway, one should expect that this mutation could affect the rate of amyloid formation as well. In the current work, we have compared the effects of amino acid substitutions of bovine carbonic anhydrase II on its unfolding pathway and on its ability to form amyloids at acidic pH and an elevated temperature. Wild-type protein and four mutant forms (L78A, L139A, I208A, and M239A) were studied. We analyzed the change of the protein unfolding pathway by the time-resolved fluorescence technique and the process of amyloid formation by thioflavin T fluorescence assay and electron microscopy. It was revealed that I208A substitution accelerates amyloid formation and affects the structure of the late (molten globule-like)-intermediate state of carbonic anhydrase, whereas the other mutations slow down the growth of amyloids and have either no effect on the unfolding pathway (L78A, L139A) or alter the conformational states arising at the early unfolding stage (M239A)

X-ray diffraction and electron microscopy data for amyloid formation of Aβ40 and Aβ42

The data presented in this article are related to the research article entitled “One of the possible mechanisms of amyloid fibrils formation based on the sizes of primary and secondary folding nuclei of Aβ40 and Aβ42” (Dovidchenko et al., 2016) [1]. Aβ peptide is one of the most intensively studied amyloidogenic peptides. Despite the huge number of articles devoted to studying different fragments of Aβ peptide there are only several papers with correct kinetics data, also there are a few papers with X-ray data, especially for Aβ42. Our data present X-ray diffraction patterns both for Aβ40 and Aβ42 as well for Tris–HCl and wax. Moreover, our data provide kinetics of amyloid formation by recombinant Аβ40 and synthetic Аβ42 peptides by using electron microscopy