Analysis of Colubroidea snake venoms by liquid chromatography with mass spectrometry: evolutionary and toxinological implications

The evolution of the venomous function of snakes and the diversification of the toxins has been of tremendous research interest and considerable debate. It has become recently evident that the evolution of the toxins in the advanced snakes (Colubroidea) predated the evolution of the advanced, front-fanged delivery mechanisms. Historically, the venoms of snakes lacking front-fanged venom-delivery systems (conventionally grouped into the paraphyletic family Colubridae) have been largely neglected. In this study we used liquid chromatography with mass spectrometry (LC/MS) to analyze a large number of venoms from a wide array of species representing the major advanced snake clades Atractaspididae, Colubrinae, Elapidae, Homalopsinae, Natricinae, Psammophiinae, Pseudoxyrhophiinae, Xenodontinae, and Viperidae. We also present the first sequences of toxins from Azemiops feae as well as additional toxin sequences from the Colubrinae. The large body of data on molecular masses and retention times thus assembled demonstrates a hitherto unsuspected diversity of toxins in all lineages, having implications ranging from clinical management of envenomings to venom evolution to the use of isolated toxins as leads for drug design and development. Although definitive assignment of a toxin to a protein family can only be done through demonstrated structural studies such as N-terminal sequencing, the molecular mass data complemented by LC retention information, presented here, do permit formulation of reasonable hypotheses concerning snake venom evolution and potential clinical effects to a degree not possible till now, and some hypotheses of this kind are proposed here. The data will also be useful in biodiscovery.     

Electrochemistry of coordination compounds: XIII. Ruthenium(I) and ruthenium(0) complexes generated by electrochemical reduction of chlorodi-(1,3-bisdiphenylphosphinopropane)ruthenium(II)-hexafluorophosphate

The electrochemical reduction of chlorodi-(1,3-bisdiphenylphosphinopropane)ruthenium(II)hexafluorophosphate, [RuCl(DPP)₂](PF₆), has been studied on the mercury electrode in 1,2-dimethoxyethane +0.1 M TBAP. The polarogram shows two reversible one-electron waves corresponding to the formation of [RuCl(DPP)₂] and [RuCl(DPP)₂]. Both products are unstable and decay through a disproportionation pathway and a fast internal metalation via Cl^? elimination with formation of HRu(C₆H₄PPh·CH₂CH₂ CH₂·PPh₂)(DPP), respectively. The hypothesis is put forward that the geometry of a metal-complex can be one of the factors which allow us to obtain d⁷ monomeric complexes by electrochemical methods.     

Color centres in crystalline Lif films

Abstract

Policrystalline LiF thin films were produced on amorphous substrates at different temperatures. Preliminary optical measurements on F₂ and F₃ ⁺ aggregate color centres produced by electron irradiation were performed.     

Solvent-Free Microwave-Assisted Organic Reactions Preparation of β-Keto Esters

Microwave technique has been utilised in the preparation of β-keto esters. Two different procedures are described: transesterification of β-keto esters and ring opening of 2,2,6-trimethyl-1,3-dioxin-4-one.     

Enrichments of post‐translational modifications in proteomic studies

More than 300 different protein post‐translational modifications are currently known, but only a few have been extensively investigated because modified proteoforms are commonly present in sub‐stoichiometry amount. For this reason, improvement of specific enrichment techniques is particularly useful for the proteomic characterization of post‐translationally modified proteins. Enrichment proteomic strategies could help the researcher in the challenging issue to decipher the complex molecular cross‐talk existing between the different factors influencing the cellular pathways. In this review the state of art of the platforms applied for the enrichment of specific and most common post‐translational modifications, such as glycosylation and glycation, phosphorylation, sulfation, redox modifications (i.e. sulfydration and nitrosylation), methylation, acetylation, and ubiquitinylation, are described. Enrichments strategies applied to characterize less studied post‐translational modifications are also briefly discussed.     

Protein structure prediction and biomolecular recognition: from protein sequence to peptidomimetic design with the human beta3 integrin

Computational tools can bridge the gap between sequence and protein 3D structure based on the notion that information is to be retrieved from the databases and that knowledge-based methods can help in approaching a solution of the protein-folding problem. To this aim our group has implemented neural network-based predictors capable of performing with some success in different tasks, including predictions of the secondary structure of globular and membrane proteins, the topology of membrane proteins and porins and stable alpha-helical segments suited for protein design. Moreover we have developed methods for predicting contact maps in proteins and the probability of finding a cysteine in a disulfide bridge, tools which can contribute to the goal of predicting the 3D structure starting from the sequence (the so called ab initio prediction). All our predictors take advantage of evolution information derived from the structural alignments of homologous (evolutionary related) proteins and taken from the sequence and structure databases. When it is necessary to build models for proteins of unknown spatial structure, which have very little homology with other proteins of known structure, non-standard techniques need to be developed and the tools for protein structure predictions may help in protein modeling. The results of a recent simulation performed in our lab highlights the role of high performing computing technology and of tools of computational biology in protein modeling and peptidomimetic design.     

Radiative recombination associated with a two-dimensional space charge layer in silicon

We present photoluminescence measurements in Si-MOS structures in presence of a two-dimensional space charge layer. A unique feature is observed: the electron-hole droplet and exciton recombinations are quenched, and a new radiative recombination channel appears, in presence of an electron space charge layer at the (1 1 1) and the (1 1 0) surfaces and of a hole space charge layer in the (1 0 0) surface. The dependence of the energy of this new band on the two-dimensional carrier concentrations is given and a simple model to explain the observed features is proposed.     

Stereoselective iodocyclization of 3-acylamino-2-methylene alkanoates: synthesis of analogues of N-benzoyl-syn-phenylisoserine

[reaction: see text] A convenient approach to racemic analogues of N-benzoyl-syn-phenylisoserine was realized via the stereoselective iodocyclization of amides obtained from Baylis-Hillman adducts.