Differential assembly of polypeptides of the light-harvesting 2 complex encoded by distinct operons during acclimation of Rhodobacter sphaeroides to low light intensity

In order to obtain an improved understanding of the assembly of the bacterial photosynthetic apparatus, we have conducted a proteomic analysis of pigment-protein complexes isolated from the purple bacterium Rhodobacter sphaeroides undergoing acclimation to reduced incident light intensity. Photoheterotrophically growing cells were shifted from 1,100 to 100?W/m(2) and intracytoplasmic membrane (ICM) vesicles isolated over 24-h were subjected to clear native polyacrylamide gel electrophoresis. Bands containing the LH2 and reaction center (RC)-LH1 complexes were excised and subjected to in-gel trypsin digestion followed by liquid chromatography (LC)-mass spectroscopy (MS)/MS. The results revealed that the LH2 band contained distinct levels of the LH2-α and -β polypeptides encoded by the two puc operons. Polypeptide subunits encoded by the puc2AB operon predominated under high light and in the early stages of acclimation to low light, while after 24?h, the puc1BAC components were most abundant. Surprisingly, the Puc2A polypeptide containing a 251 residue C-terminal extension not present in Puc1A, was a protein of major abundance. A predominance of Puc2A components in the LH2 complex formed at high light intensity is followed by a >2.5-fold enrichment in Puc1B levels between 3 and 24?h of acclimation, accompanied by a nearly twofold decrease in Puc2A levels. This indicates that the puc1BAC operon is under more stringent light control, thought to reflect differences in the puc1 upstream regulatory region. In contrast, elevated levels of Puc2 polypeptides were seen 48?h after the gratuitous induction of ICM formation at low aeration in the dark, while after 24?h of acclimation to low light, an absence of alterations in Puc polypeptide distributions was observed in the upper LH2-enriched gel band, despite an approximate twofold increase in overall LH2 levels. This is consistent with the origin of this band from a pool of LH2 laid down early in development that is distinct from subsequently assembled LH2-only domains, forming the LH2 gel band.     

Hatching late in the season requires flexibility in the timing of song learning

Most songbirds learn their songs from adult tutors, who can be their father or other male conspecifics. However, the variables that control song learning in a natural social context are largely unknown. We investigated whether the time of hatching of male domesticated canaries has an impact on their song development and on the neuroendocrine parameters of the song control system. Average age difference between early- and late-hatched males was 50 days with a maximum of 90 days. Song activity of adult tutor males decreased significantly during the breeding season. While early-hatched males were exposed to tutor songs for on average the first 99 days, late-hatched peers heard adult song only during the first 48 days of life. Remarkably, although hatching late in the season negatively affected body condition, no differences between both groups of males were found in song characteristics either in autumn or in the following spring. Similarly, hatching date had no effect on song nucleus size and circulating testosterone levels. Our data suggest that late-hatched males must have undergone accelerated song development. Furthermore, the limited tutor song exposure did not affect adult song organization and song performance.     

Co-Inheritance of alpha-thalassemia and sickle cell disease in a cohort of Angolan pediatric patients

Molecular Biology Reports - The aim of this study was to explore the association between alpha-thalassemia, fetal hemoglobin, hematological indices, and clinical adverse events in Angolan sickle...     

Steady-state luminescence investigation of the binding of Eu(III) and Tb(III) ions with synthetic peptides derived from plant thionins

This work reports Eu(III) and Tb(III) luminescence titrations in which the lanthanide ions were used as spectroscopic probes for Ca(II) ions to determine the metal binding ability of Ac-NESVKEEGGW-NH(2) and Ac-NESVKEDGGW-NH(2). These decapeptides correspond to the putative calcium binding region of the plant antifungal proteins SI-alpha1 from Sorghum bicolor and of Zeathionin from Zea mays, respectively. The luminescence spectra for the Eu(III)-decapeptide system (red emission) with the excitation at the Trp band at 280 nm showed an enhancement of the intensities of the 5D(0)-->7F(J) transitions (where J=0-4) with increments of Eu(III) ion concentration. The photoluminescence titration data of the terbium ion (green emission) in the decapeptide solutions showed intensification of the 5D(4)-->7F(J) transitions (J=0-6), similar to that observed for the Eu(III) ion. Thus, energy transfer from Ac-NESVKEEGGW-NH(2) and Ac-NESVKEDGGW-NH(2) to the trivalent lanthanide ions revealed that these peptides are capable of binding to these metal ions with association constants of the order of 10(5) M(-1). The amino acid derivative Ac-Trp-OEt also transferred energy to Tb(III) and Eu(III) ions as judged from the quenching of tryptophan luminescence. However, the energy transfers were significantly lower. Taken together the luminescence titration data indicated that Ac-NESVKEEGGW-NH(2) and Ac-NESVKEDGGW-NH(2) bind efficiently to both trivalent lanthanide ions and that these ions may be used as probes to distinguish an anionic peptide from a neutral amino acid derivative.