Skull osteology and osteological phylogeny of the Western whip snake Hierophis viridiflavus (Squamata,Colubridae)

The skull osteology of Hierophis viridiflavus is here described and figured in detail on the basis of 18 specimens. The sample includes specimens from the ranges of both H. viridiflavus viridiflavus and H. viridiflavus carbonarius as well as specimens not identified at sub-specific level. The main characters that define H. viridiflavus in comparison to the parapatric congeneric species Hierophis gemonensis are wide maxillary diastema, basioccipital crest well distinct in three lobes and basioccipital process well marked. The foramina of the otoccipital and prootic, and the basioccipital process of the basioccipital are among the most ontogenetically variable characters, as indicated by two juvenile specimens included in the sample. A specimen-level phylogenetic analysis including H. gemonensis and other outgroups (overall 6 species, 26 specimens, 64 skull characters) recovered all H. viridiflavus specimens in one clade, indicating the presence of a clear phylogenetic signal in the applied characters. However, the resolution within the H. viridiflavus clade is poor the monophyly of H. viridiflavus carbonarius was retrieved, but not that of Hierophis v. viridiflavus. Probably due to the relatively high variability, the skull morphology does not support the recently proposed specific status of the two subspecies.     

Developmental phenotypic plasticity: Where ecology and evolution meet molecular biology

The plastic response of phenotypic traits to environmental change is a common research focus in several disciplines - from ecology and evolutionary biology to physiology and molecular genetics. The use of model systems such as the flowering plant Arabidopsis thaliana has facilitated a dialogue between developmental biologists asking how plasticity is controlled (proximate causes) and organismal biologists asking why plasticity exists (ultimate causes). Researchers studying ultimate causes and consequences are increasingly compelled to reject simplistic, ‘black box’ models, while those studying proximate causes and mechanisms are increasingly obliged to subject their interpretations to ecological ‘reality checks.’ We review the successful multidisciplinary efforts to understand the phytochrome-mediated shade-avoidance and light-seeking responses of flowering plants as a pertinent example of convergence between evolutionary and molecular biology. In this example, the two-way exchange between reductionist and holist camps has been essential to rapid and sustained progress. This should serve as a model for future collaborative efforts towards understanding the responses of organisms to their constantly changing environments.     

Identification, sequencing and mutagenesis of the gene for a d-carbamoylase from Agrobacterium radiobacter

Abstract A clone positive for d-carbamoylase activity (2.7 kb Hin dIII- Bam H1 DNA fragment) was obtained by screening a genomic library of Agrobacterium radiobacter in Escherichia coli . This DNA fragment contains an open reading frame of 912 bp which is predicted to encode a peptide of 304 amino acids with a calculated molecular mass of 34247 Da. The d-carbamoylase gene. named cauA , was placed under the control of T7 RNA-dependent promoter and expressed in E. coli BL21 (DE3). After induction with isopropyl-thio-β-d-galactopyranoside, the synthesis of d-carbamoylase in E. coli reached about 40% of the total protein. The expressed protein was shown to possess a molecular mass, on SDS-PAGE, of 36 kDa and showed an enhanced allowed us to establish that a Pro¹⁴→Leu¹⁴ exchange leads to an inactive enzyme species, while a Cys²⁷⁹→Ser²⁷⁹ exchange did not impair the functional properties of the enxyme.     

Studies on light absorption and photochemical activity changes in chloroplast suspensions and leaves due to light scattering and light filtration across chloroplast and vegetation layers

An experimental analysis is presented concerning the effect on relative light absorption by the two photosystems caused by (a) a highly light scattering environment (the detour effect) and (b) light filtration across successive chloroplast layers (the light attenuation effect). Both suspensions of isolated chloroplasts and leaves were employed.It is concluded that within a single spinach leaf these phenomena are likely to lead to only rather small increases in relative photosystem I absorption and activity with respect to photosystem II and will thus not exert a significant effect on non cyclic electron transport. On the contrary when light is filtrated across successive vegetation layers (shade light) significant increases in the relative PSI absorption and activity may be encountered.It is determined that the detour effect in mature leaves from a variety of plants increases overall photosynthetically useful light absorption by 35–40%.Abbreviations F_M maximal fluorescence - LHCP₂ light-harvesting chlorophyl a/b protein complex II - Q_A-primary quinone acceptor of photosystem II     

Thermodynamic modeling of internal equilibria involved in the activation of trypsinogen

The effect of activating dipeptides, sequentially homologous to the Ile16-Val17N-terminus of bovine beta-trypsin (beta-trypsin), on equilibria involved in the binding of strong ligands (i.e., n-butylamine, the bovine basic pancreatic trypsin inhibitor (Kunitz-type inhibitor; BPTI) and the porcine pancreatic secretory trypsin inhibitor (Kazal-type inhibitor, type I; PSTI)) to bovine trypsinogen (trypsinogen) was investigated at pH 5.51 (I = 0.1 M) and T = 21.0 +/- 0.5 degrees C; under the same experimental conditions, thermodynamics for the binding of strong ligands to beta-trypsin was also obtained. The equilibria involved in the binding of activating dipeptides and/or inhibitors to beta-trypsin and to its zymogen are described according to an induced-fit formalism, taking into account ligand-linked interaction(s) between different functional and structural domains of the (pro)enzyme possibly involved in the trypsinogen-to-beta-trypsin activation pathway. The analysis of data is focussed on parameters describing interactions between the so-called Ile-Val pocket (where the Ile16-Val17 N-terminus of beta-trypsin or activating dipeptides bind) and the primary and/or secondary recognition subsite(s) (where strong ligands associate) present in the (pro)enzyme. Such an analysis allows to dissect the contributions due to the primary recognition subsite, where small mono-functional ligands (e.g., n-butylamine) bind, from those of the secondary subsite(s), which are additional recognition clefts for macromolecular inhibitors (e.g., BPTI and PSTI).