Potassium Ions are More Effective than Sodium Ions in Salt Induced Peptide Formation

Prebiotic peptide formation under aqueous conditions in the presence of metal ions is one of the plausible triggers of the emergence of life. The salt-induced peptide formation reaction has been suggested as being prebiotically relevant and was examined for the formation of peptides in NaCl solutions. In previous work we have argued that the first protocell could have emerged in KCl solution. Using HPLC-MS/MS analysis, we found that K(+) is more than an order of magnitude more effective in the L-glutamic acid oligomerization with 1,1'-carbonyldiimidazole in aqueous solutions than the same concentration of Na(+), which is consistent with the diffusion theory calculations. We anticipate that prebiotic peptides could have formed with K(+) as the driving force, not Na(+), as commonly believed

Fluorescence of the retinal chromophore in microbial and animal rhodopsins

Fluorescence of the vast majority of natural opsin-based photoactive proteins is extremely low in accordance with their functions that depend on efficient transduction of absorbed light energy. However, recently proposed several classes of engineered rhodopsins with enhanced fluorescence along with the discovery of a new natural highly fluorescent rhodopsin, NeoR, opened a way to exploit these transmembrane proteins as fluorescent sensors and draw more attention to studies on this untypical rhodopsins property. Here we review available data on the fluorescence of the retinal chromophore in microbial and animal rhodopsins and their photocycle intermediates as well as different isomers of the protonated retinal Schiff base in different solvents and the gas phase

Ruthenium-Based Electrode Modified by Gold Particles as Voltammetric Sensor for Non-Enzymatic Epinephrine Detection

A simple and efficient technique for voltammetric enzymeless detection of epinephrine (EP) is proposed. The technique applies hierarchical Ru-based electrodes modified by Au nano- to micro-sized particles, which were produced with laser-assisted synthesis. The cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were employed to characterize electrochemical properties of the electrodes. For EP detection, we obtained two DPV calibration curves that are linear in the range of 0.01-5 μM and 5-500 μM. The highest sensitivity (46.9 μA μM−1 cm−2) and the lowest detection limit (6.1 nM) are observed for the first linear range, whereas the estimated sensitivity and limit of detection for the second linear range are 2.1 μA μM−1 cm−2 and 17.8 nM, respectively. We also demonstrated that the proposed technique can be used for selective EP determination in the presence of such common interfering analytes as ascorbic acid and dopamine. The results of this study can be employed for development of low-cost voltammetric sensor platforms for non-enzymatic epinephrine detection in a physiological environment

Molecular mechanisms of adaptation to the habitat depth in visual pigments of A. subulata and L. forbesi squids: on the role of the S270F substitution

Revealing the mechanisms of animal adaptation to different habitats is one of the central tasks of evolutionary physiology. A particular case of such adaptation is the visual adaptation of marine species to different depth ranges. Because water absorbs more intensively longer wavelengths than shorter wavelengths, the increase of habitat depth shifts the visual perception of marine species towards the blue region. In this study, we investigated the molecular mechanisms of such visual adaptation for two squid species – Alloteuthis subulata and Loligo forbesi. These species live at different depths (200 m and 360 m, respectively) and the absorption maximum of A. subulata visual rhodopsin is slightly red-shifted compared to L. forbesi rhodopsin (499 and 494 nm, respectively). Previously, the amino acid sequences of these two species were found to differ in 22 sites with only seven of them being non-neutral substitutions, and the S270F substitution was proposed as a possible candidate responsible for the spectral shift. In this study, we constructed computational models of visual rhodopsins of these two squid species and determined the main factors that cause the 5 nm spectral shift between the two proteins. We find that the origin of this spectral shift is a consequence of a complex reorganization of the protein caused by at least two mutations including S270F. Moreover, the direct electrostatic effect of polar hydroxyl-bearing serine that replaces non-polar phenylalanine is negligible due to the relatively long distance to the chromophore