Quantitative assessment of peptide-lipid interactions.: Ubiquitous fluorescence methodologies

Peptide-membrane interactions have been gaining increased relevance, mainly in biomedical investigation, as the potential of the natural, nature-based and synthetic peptides as new drugs or drug candidates also expands. These peptides must face the cell membrane when they interfere with or participate in intracellular processes. Additionally, several peptide drugs and drug leads actions occur at the membrane level (e.g., antimicrobial peptides, cell-penetrating peptides and enveloped viruses membrane fusion inhibitors). Here we explore fluorescence spectroscopy methods that can be used to monitor such interactions. Two main approaches are considered, centered either on the peptide or on the membrane. On the first, we consider mainly the methodologies based on the intrinsic fluorescence of the aminoacid residues tryptophan and tyrosine. Regarding membrane-centric approaches, we review methods based on lipophilic probes sensitive to membrane potentials. The use of fluorescence constitutes a simple and sensitive method to measure these events. Unraveling the molecular mechanisms that govern these interactions can unlock the key to understand specific biological processes involving natural peptides or to optimize the action of a peptide drug.     

Male dispersal patterns in white-faced capuchins, Cebus capucinus: Part 2: patterns and causes of secondary dispersal

Male dispersal from the birth group is common in the majority of social mammals, and in many species, males also engage in secondary or breeding dispersal following natal emigration. However, the patterns and causes of secondary dispersal are poorly understood due to the difficulty in following emigrants. Here, we detail the patterns and causation of male secondary dispersal in several groups of white-faced capuchins observed between 1985 and 2000 in Santa Rosa National Park, Costa Rica. Subsequent to natal emigration, which occurs between 2 and 8 years of age (median 4.5 years), male white-faced capuchins embark on a life of continual movement. Although males of all age classes engage in voluntary secondary dispersal, the ways by which males enter groups varies according to their age class. Adult males (≥10 years old) are more likely to enter groups aggressively, and they display longer tenure than either subadult males (7-10 years of age) or juvenile males (1-7 years of age). Given our finding that adult males face the highest risks in terms of aggressive interactions with conspecifics, we examined several explanations as to why they continue to disperse throughout their lives. Our data best support the intragroup mating competition hypothesis for secondary dispersal, whereby males move frequently between groups as a means of increasing their reproductive opportunities. Males may also engage in frequent secondary dispersal to avoid mating with their maturing daughters, although this hypothesis was not strongly supported by the current data. Males of all age classes displayed very high levels of parallel dispersal, which probably serves to offset the high costs of dispersal (predation, starvation and/or aggression from conspecifics) and it may also serve as a means of retaining kinship among group males.     

Fluorinated carbohydrates : Part XIII. 2-deoxy-2-fluoro-D-galactose

Reaction of trifluoro(fluoroxy)methane at ca. −80° with 3,4,6-tri-O-acetyl-D-galactal affords trifluoromethyl 3,4,6-tri-O-acetyl-2-deoxy-2-fluoro-α-D-galactopyranoside (2, 39%), 3,4,6-tri-O-acetyl-2-deoxy-2-fluoro-α-D-galactopyranosyl fluoride (3, 37%), trifluoromethyl 3,4,6-tri-O-acetyl-2-deoxy-2-fluoro-α-D-talopyranoside (4, 3%), and 3,4,6-tri-O-acetyl-2-deoxy-2-fluor-α-D-talopyranosyl fluoride (5, 2%). The structures of compounds 2–5 have been established by n.m.r. spectroscopy. Acid hydrolysis of 2 or 3 allords 2-deoxy-2-fluoro-D-galactose.