A holomorphic characterization of compact sets in Banach spaces

An extension of Lempert’s result about non approximability by entire functions of analytic functions on some open subsets of ?_∞ is obtained for Banach spaces having a bounding non relatively compact set.We also prove that subsets A that are bounding for analytic functions defined in any of its neighborhoodswhose boundary lies at positive distance from A are relatively compact.     

Complexity of "A-a" knob-hole fibrin interaction revealed by atomic force spectroscopy

During blood vessel injury, fibrinogen is converted to fibrin, a polymer that serves as the structural scaffold of a blood clot. The primary function of fibrin is to withstand the large shear forces in blood and provide mechanical stability to the clot, protecting the wound. Understanding the biophysical forces involved in maintaining fibrin structure is of great interest to the biomedical community. Previous reports have identified the "A-a" knob-hole interaction as the dominant force responsible for fibrin's structural integrity. Herein, biochemical force spectroscopy is used to study knob-hole interactions between fibrin fragments and variant fibrinogen molecules to identify the forces occurring between individual fibrin molecules. The rupture of the "A-a" knob-hole interaction results in a characteristic profile previously unreported in fibrin force spectroscopy with two distinct populations of specific forces: 110 +/- 34 and 224 +/- 31 pN. In the absence of a functional "A" knob or hole "a", these forces cease to exist. We propose that the characteristic pattern represents the deformation of the D region of fibrinogen prior to the rupture of the "A-a" knob-hole bond.     

How does the coupling of secondary and tertiary interactions control the folding of helical macromolecules?

The authors study how the simultaneous presence of short-range secondary and long-range tertiary interactions controls the folding and collapse behavior of a helical macromolecule. The secondary interactions stabilize the helical conformation of the chain, while the tertiary interactions govern its overall three-dimensional shape. The authors have carried out Monte Carlo simulations to study the effect of chain length on the folding and collapse behavior of the chain. They have calculated state diagrams for four chain lengths and found that the physics is very rich with a plethora of stable conformational states. In addition to the helix-coil and coil-globule transitions, their model describes the coupling between them which takes place at low temperatures. Under these conditions, their model predicts a cascade of continuous, conformational transitions between states with an increase in the strength of the tertiary interactions. During each transition the chain shrinks, i.e., collapses, in a rapid and specific manner. In addition, the number of the transitions increases with increasing chain length. They have also found that the low-temperature regions of the state diagram between the transition lines cannot be associated with specific structures of the chain, but rather, with ensembles of various configurations of the chain with similar characteristics. Based on these results the authors propose a mechanism for the folding and collapse of helical macromolecules which is further supported by the analysis of configurational, configurational, and thermodynamic properties of the chain.     

Sample classification for improved performance of PLS models applied to the quality control of deep-frying oils of different botanic origins analyzed using ATR-FTIR spectroscopy

The selection of an appropriate calibration set is a critical step in multivariate method development. In this work, the effect of using different calibration sets, based on a previous classification of unknown samples, on the partial least squares (PLS) regression model performance has been discussed. As an example, attenuated total reflection (ATR) mid-infrared spectra of deep-fried vegetable oil samples from three botanical origins (olive, sunflower, and corn oil), with increasing polymerized triacylglyceride (PTG) content induced by a deep-frying process were employed. The use of a one-class-classifier partial least squares-discriminant analysis (PLS-DA) and a rooted binary directed acyclic graph tree provided accurate oil classification. Oil samples fried without foodstuff could be classified correctly, independent of their PTG content. However, class separation of oil samples fried with foodstuff, was less evident. The combined use of double-cross model validation with permutation testing was used to validate the obtained PLS-DA classification models, confirming the results. To discuss the usefulness of the selection of an appropriate PLS calibration set, the PTG content was determined by calculating a PLS model based on the previously selected classes. In comparison to a PLS model calculated using a pooled calibration set containing samples from all classes, the root mean square error of prediction could be improved significantly using PLS models based on the selected calibration sets using PLS-DA, ranging between 1.06 and 2.91% (w/w).     

Biholomorphic Functions in Dual Banach Spaces

We present an infinite-dimensional version of Cartan-Carathéodory-Kaup-Wu theorem about the analyticity of the inverse of a given analytic mapping. It is valid for a class of domains in separable Banach dual spaces that includes all bounded convex domains.     

Synthesis and X-ray structure of a fluorinated 1,1-dialkoxy-3-iminoisoindoline acetal,an elusive phthalocyanine precursor

The synthesis of a fluoroalkylated 1,1-dimethoxy-3-iminoisoindoline acetal, the first representative of the halogenated 3-imino-amino-1-acetal class is reported. In contrast to the protio compound, fluoroalkyl groups make the presence of a base unnecessary for its synthesis while stabilizing the amino tautomer as revealed by an X-ray structural analysis - the first atomic-level structural characterization of the 1,1-alkoxy-3-amino(imino) isoindoline scaffold. Dimers present in solid-state are H-bonded and define a motif similar to the stabilizing, reverse wobble one encountered in adenine-cytosine pairs of tRNA. The fluoro acetal forms easily both metallo- and metal-free phthalocyanines, supporting the proposal that acetals might be phthalocyanine intermediates.     

Comportement sous impact electronique d'allenes ω-fonctionnels et des acetyleniques isomeres. Mise en evidence du transfert d'un chlore et d'un hydroxyle par un rearrangement de type mclafferty a l'aide de la spectrometrie cid-mike.

This paper describes the use of collision induced dissociation spectra in structural elucidation of C₄H₅X^+. ions, formed by chlorine or hydroxyl group migration in a McLafferty type rearrangement of the molecular ion of (ω-functionnalized allenes and their isomeric acetylenes.     

The C-terminal domain of pancreatic lipase: functional and structural analogies with c2 domains

The 3D structure of pancreatic lipase (PL) consists of two functional domains. The N-terminal domain belongs to the alpha/beta hydrolase fold and contains the active site, which involves a catalytic triad analogous to that present in serine proteases. The beta-sandwich C-terminal domain of PL plays an important part in the binding process between the lipase and colipase, the specific PL cofactor. Recent structure-function studies have suggested that the PL C-terminal domain may have an extra role apart from that of binding colipase. This domain contains an exposed hydrophobic loop (beta5') which was found to be located on the same side as the hydrophobic loops surrounding the active site, and it may be involved in the lipid binding process. Indirect evidence for this new function of the PL C-terminal domain has been provided by studies with monoclonal antibodies directed against the beta5' loop. The catalytic activity of the PL-antibody complexes on water insoluble substrates decreased drastically, whereas their esterase activity on a soluble substrate remained unchanged. During the last few years, a number of protein structures (15-lipoxygenase, alpha-toxin from Clostridium perfringens) have been determined that contain domains with close structural homologies with the beta-sandwich C-terminal domain of PL. Generally speaking, these domains show structural homologies with the C2 domains occurring in a wide range of proteins involved in signal transduction (e.g. phosphoinositide-specific phospholipase C, protein kinase C, cytosolic phospholipase A2), membrane traffic (e.g. synaptotagmin I, rabphilin) and membrane disruption (e.g. perforin). Here it is proposed to review the structure and function of the C2 domains, based on the recent 3D structures and improved sequence alignments.