Organic solvents may induce non-native structures of proteins that mimic folding intermediates and/or conformations that occur in proximity to biological membranes. Here we systematically investigate the effects of simple (i.e., MeOH and EtOH) and fluorinated (i.e., trifluoroethanol, TFE) alcohols on the secondary structure and thermodynamic stability of two complementary model proteins using a combination of circular dichroism, fluorescence, and Fourier transform infrared (FTIR) detection methods. The selected proteins are alpha-helical Borrelia burgdorferi VlsE and beta-sheet human mitochondrial co-chaperonin protein 10 (cpn10). We find that switches between VlsE's native and non-native superhelical and beta-sheet structures readily occur (pH 7, 20 degrees C). The pathway depends on the alcohol: addition of MeOH induces a transition to a superhelical structure that is followed by conversion to beta-structure, whereas EtOH only unfolds the protein. TFE unfolds VlsE at low percentages but promotes the formation of a superhelical state upon further additions. For cpn10, both MeOH and TFE additions govern initial unfolding; however, further additions of MeOH result in the formation of a non-native beta-structure, whereas subsequent additions of TFE induce a superhelical structure. EtOH additions promptly unfold and precipitate cpn10. Both VlsE's and cpn10's non-native structures exhibit high stability toward chemical and thermal perturbations. This study demonstrates that in response to different alcohols, polypeptides can readily adopt both alpha- and beta-enriched conformations. The biological significance of these findings is discussed.

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As the study on microbiology deepens, human microorganism, especially intestinal microflora, has been proved to be closely related to the occurrence of many diseases. Cranial nerve injury diseases, especially large artery atherosclerosis, have a high incidence in China, which makes it the focus of disease prevention and control in China. However, no studies have been conducted on the intestinal microflora and plasma TMAO levels in patients with cranial nerve injury. In this study, the changes of intestinal microflora and its metabolites are analyzed by comparing blood and fresh stool samples from stroke patients and healthy people. The results of the study show that there are obvious disturbances in the intestinal microflora in patients with stroke, the proportion of harmful flora increases, and plasma TMAO levels decreases.