Study of the Spectral Characteristics of L-Lysine and L-Arginine Using UV-VIS Spectroscopy and Steady-State and Synchronous Fluorescence Spectroscopy

Biophysics - The recently discovered luminescent properties of nonaromatic amino acids with excitation-dependent photoluminescence in the absence of conjugation within individual molecules have...     

European checkerspots (Melitaeini: Lepidoptera,Nymphalidae) are not aposematic – the point of view of great tits (Parus major)

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A new synthetic all-D-peptide with high bacterial and low mammalian cytotoxicity

Using the synthetic alpha-helical peptide ((RLA)(2)R)(2) as a model the effect of net charge, helicity, and epimeric nature of the peptide on bactericidal potency has been examined. Both the nature and the extent of the net charge were shown to be relatively important for antibacterial activity. The loss of the structured character of the peptide resulted in reducing the activity. The all-D-peptide appeared to be a remarkably strong bacteriostatic agent with MIC <1 microM against Escherichia coli. The peptide was neither hemolytic nor cytotoxic, which in conjunction with data on its stability to enzymatic degradation makes this peptide very attractive in terms of designing new bactericidal agents on the basis of (D)((RLA)(2)R)(2).     

FTIR Emission Spectra of Bacteriorhodopsin in a Vibrational Excited-State

Vibrational IR-emission spectra of bacteriorhodopsin (bR) were recorded under continuous illumination with visible light at room temperature. They contain selective information about the chromophore, Schiff base, and opsin. The spectral bands were identified by comparing the data with resonance Raman and IR absorption data. The IR-emission spectra were shown to contain a set of bands characteristic for both all-trans (bR₅₆₈) and 13-cis conformations (K₆₁₀-like intermediate) simultaneously. Variation of spectral composition and the intensity of visible light illumination influenced the spectral traces and intensity distribution between them. Greater intensity of deformational vibrations suggests distorted retinal structure in the vibrationally excited ground electronic state. The origin of the emitting species of bR is discussed.     

Microwave-Induced Structural Changes in Bacteriorhodopsin: Studies by Optical and Fourier Transform Infrared Difference Spectroscopy

Biophysics - Abstract—Using optical and Fourier transform infrared (FTIR) difference spectroscopy, microwave radiation was found to affect the bacteriorhodopsin (BR) structure in films at a...     

ONTOGENETIC NICHE SHIFT IN THE BRACHIOPOD TEREBRATALIA TRANSVERSA: RELATIONSHIP BETWEEN THE LOSS OF ROTATION ABILITY AND ALLOMETRIC GROWTH

Abstract: Many articulated brachiopods experience marked life habit variations during ontogeny because they experience their fluid environment at successively higher Reynolds numbers, and they can change the configuration of their inhalant and exhalant flows as body size increases. We show that the extant brachiopod Terebratalia transversa undergoes a substantial ontogenetic change in reorientation governed by rotation around the pedicle. T. transversa′s reorientation angle (maximum ability to rotate on the pedicle) decreases during ontogeny, from 180 degrees in juveniles to 10–20 degrees in individuals exceeding 5 mm, to complete cessation of rotation in individuals larger than 10 mm. Rotation ability is substantially reduced after T. transversa achieves the adult lophophore configuration and preferred orientation with respect to ambient water currents at a length of 2.5–5 mm. We hypothesize that the rotation angle of T. transversa is determined mainly by the position of ventral and dorsal points of attachment of dorsal pedicle muscles relative to the pedicle. T. transversa shows a close correlation between the ontogenetic change in reorientation angle and ontogeny of morphological traits that are related to points of attachment of dorsal pedicle muscles, although other morphological features can also limit rotation in the adult stage. The major morphological change in cardinalia shape and the observed reduction of rotation affect individuals 2.5–10 mm in length. The position of ventral insertions of dorsal pedicle muscles remains constant, but contraction of dorsal pedicle muscles is functionally handicapped because dorsal insertions shift away from the valve midline, rise above the dorsal valve floor, and become limited by a wide cardinal process early in ontogeny (<5 mm). The rate of increase of cardinal process width and of distance between dorsal pedicle muscle scars substantially decreases in the subadult stage (5–10 mm), and most of the cardinalia shell traits grow nearly isometrically in the adult stage (>10 mm). T. transversa attains smaller shell length in crevices than on exposed substrates. The proportion of small‐sized individuals and population density is lower on exposed substrates than in crevices, indicating higher juvenile mortality on substrates prone to grazing and physical disturbance. The loss of reorientation ability can be a consequence of morphological changes that strengthen substrate attachment and maximize protection against biotic or physical disturbance (1) by minimizing torques around the pedicle axis and/or (2) by shifting energy investments into attachment strength at the expense of the cost involved in reorientation.     

Do Female Western Mosquitofish,Gambusia affinis,Prefer Ornaments That Males Lack?

Some species in the family Poeciliidae are known for extravagant male ornaments and courtship behavior (e.g., guppies), but the majority of poeciliids are characterized by coercive male copulation attempts that seem to circumvent female choice. In some lineages with male ornaments, female sensory bias may have preceded the evolution of corresponding male signals. We examined female preferences for colorful ornaments in Western mosquitofish, Gambusia affinis, in which males lack ornamentation and reproduce primarily through coercive mating attempts. We found that females exhibited a positional affinity for males that were artificially ornamented with blue coloration over males that had been treated with a transparent ornament. Females exhibited the opposite effect for males treated with red ornaments. In contrast, focal females did not exhibit behavioral discrimination between two live stimulus females or two models (silver fishing lures) with blue vs. transparent ornaments. This suggests a sexual context for female discrimination between males based on ornament color and whether an ornament was present. Because tribe Gambusiini is the basal branch of family Poeciliidae, the results of this study are consistent with the hypothesis that female responsiveness to male coloration is the ancestral poeciliid character state.     

Genetic factors affecting the impact of DNA polymerase delta proofreading activity on mutation avoidance in yeast

Base selectivity, proofreading, and postreplication mismatch repair are important for replication fidelity. Because proofreading plays an important role in error correction, we have investigated factors that influence its impact in the yeast Saccharomyces cerevisiae. We have utilized a sensitive mutation detection system based on homonucleotide runs of 4 to 14 bases to examine the impact of DNA polymerase delta proofreading on mutation avoidance. The contribution of DNA polymerase delta proofreading on error avoidance was found to be similar to that of DNA polymerase epsilon proofreading in short homonucleotide runs (A4 and A5) but much greater than the contribution of DNA polymerase epsilon proofreading in longer runs. We have identified an intraprotein interaction affecting mutation prevention that results from mutations in the replication and the proofreading regions, resulting in an antimutator phenotype relative to a proofreading defect. Finally, a diploid strain with a defect in DNA polymerase delta proofreading exhibits a higher mutation rate than a haploid strain. We suggest that in the diploid population of proofreading defective cells there exists a transiently hypermutable fraction that would be inviable if cells were haploids.