Deuterium labeled peptides give insights into the directionality of class III lantibiotic synthetase LabKC

The biosynthesis of a considerable number of ribosomally synthesized peptide antibiotics involves the modification of Ser and Thr residues of a precursor peptide. This post-translational processing is performed by one or multiple modifying enzymes encoded in the biosynthetic gene cluster. We present a deuterium-label based enzyme assay, utilizing a series of peptide substrates with α-deuterated Ser, for the determination of the dehydration order during the biosynthesis of class III lantibiotic labyrinthopeptin A2. Remarkably, the data show that, in contrast to other modifying enzymes of class I and II lantibiotics, LabKC has a C- to N-terminal processing mode. This surprising finding, which we consider relevant for the biosyntheses of other class III lantibiotics, underlines significant differences of this class of modifying enzymes compared to other investigated systems.     

The Topological Gradient Method: From Optimal Design to Image Processing

The aim of this article is to review and extend the applications of the topological gradient to major image processing problems. We briefly review the topological gradient, and then present its application to the crack localization problem, which can be solved using the Dirichlet to Neumann approach. A very natural application of this technique in image processing is the inpainting problem, which can be solved by identifying the optimal location of the missing edges. Edge detection is of extreme importance, as edges convey essential information in a picture. A second natural application is then the image reconstruction. A class of image reconstruction problems is considered that includes restoration, demosaicing, segmentation and super-resolution. These problems are studied using a unified theoretical framework which is based on the topological gradient method. This tool is able to find the localization and orientation of the edges for blurred, low sampled, partially masked, noisy images. We review existing algorithms and propose new ones. The performance of our approach is compared with conventional image reconstruction processes.     

On-line version of Rabinovitch theorem for proper intervals

We analyze the on-line dimension of semi-orders as a two-person game between Algorithm and Spoiler, in a customary way. The game is played in rounds. Spoiler presents a collection of intervals representing a semi-order, one interval at a time. Algorithm maintains its realizer, i.e., the set of linear extensions intersecting the semi-order presented so far. Each time a new interval is presented, Algorithm inserts it into all maintained linear extensions and is not allowed to change the ordering of the previously introduced elements. Reading carefully the theorem of Rabinovitch on dimension of semi-orders one can prove that Algorithm needs only 3 linear extensions when Spoiler presents intervals of unit length. With the introduction of proper intervals, however, Algorithm can be forced to use one more extension. We prove that the value of the game on proper intervals is exactly 4.     

( S )-(?)-α-Methylbenzylamine as chiral auxiliary in the synthesis of (+)-lortalamine

Abstract  

(+)-Lortalamine was synthesised using (S)-(−)-α-methylbenzylamine as a chiral auxiliary. The stereochemistry of an intermediate compound was established on the basis of X-ray crystallography, allowing unambiguous assignment of the absolute configuration.     

Facile detection of proteins on a solid-phase membrane by direct binding of dextran-based luminol-biotin chemiluminescent polymer

Facile and non-radioactive methods are desired for the sensitive detection and quantification of various proteins. Herein we describe a novel chemiluminescence (CL)-detection method of particular proteins based on direct binding of a dextran-luminol-biotin (DLB) CL polymer to the proteins on a poly(vinylidene difluoride) membrane. Among 32 kinds of the proteins screened, several proteins such as drug-metabolizing enzymes, cytochrome p450 (CYP)1A2, CYP2E1, and CYP3A4 had the ability to bind directly to the DLB polymer. The binding site in the polymer was owing to the framework of the modified dextran, which underwent oxidation and reduction procedures. This interaction might be the comprehensive effect of both electrostatic interaction and steric complementarities. CL intensity of the proteins detected by the polymer could be further enlarged by the mediation of avidin. The proposed CL-imaging method possesses potential as a rapid, facile, inexpensive and selective detection of the proteins.     

Glycosylated Hematoporphyrins: A New Approach in Cancer Phototherapy?

ABSTRACT

Although the phenomenon is not fully understood, it is now well established that some porphyrins have a natural tendency to concentrate more in malignant tumors than in normal tissue. This property has found an application in photodynamic therapy of cancers in which a tumor, with an enriched concentration of porphyrin, can be selectively destroyed by applying light, without damage to surrounding cells.¹     

Alkylidenation of Sugar Lactones and Further Transformation to C-Glycosides

ABSTRACT

The Witting reaction of (carbethoxymethylene)triphenylphosphorane with perbenzylated sugar δ-lactones and their 2-acetamido-2-deoxy derivatives is described. It is shown that this olefination occurred readily with the galacto and gluco derivatives, leading stereoselectively to Z-C-glycosylidenes in good yields. However, the same reaction with the perbenzylated 2-deoxy-D-arabino-hexono-1,5-lactone and the mannonolactones worked poorly. Reduction over Pd/C followed by acetylation of the obtained C-glycosylidenes led stereoselectively to peracetylated β-C-glycosides and amino β-C-glycosides. The olefin function could also be reduced selectively by Raney nickel or NiCl₂/NaBH₄, affording the perbenzylated C-glycosides and amino β-C-glycosides. Other transformation of the enol ether function is also reported.     

The Mannich Reaction of Diethyl Phosphonoacetic Acid. A Novel Route to 1-(N,N-Dialkylamino)methylvinylphosphonates

The Mannich reaction of diethyl phosphonoacetic acid (4) provides a short and efficient approach to vinylphosphonates 6.     

EPR study of coke formed on alumina

This study was aimed at characterizing paramagnetic properties of cokes formed on aluminas of different origin (calcined at 400 and 800°C) during catalytic reactions of hexafluoro-2-propanol decomposition and, for the sake of comparison, 2-propanol decomposition at 300 and 400°C. No significant differences in coke-forming activities were found between alumina obtained by hydrolysis of aluminium isopropoxide and that prepared by precipitation with ammonia from aluminium sulfate solution at pH 6.1, although they differed substantially in their acidity patterns. On the other hand, clear differences were observed between intensities of electron paramagnetic resonance (EPR) spectra recorded for samples covered with coke produced by reactions of the two alcohols. When hexafluoro-2-propanol was the parent substance, spectral lines were stronger and narrower than those obtained for 2-propanol. The smaller linewidth (ΔB _pp=0.29-0.54 mT compared to ΔB _pp=0.51-0.92 mT) was most likely a result of exchange interactions between electrons of paramagnetic centers, whose concentrations were higher in the carbonaceous deposit formed from fluorine-containing alcohol. Higher temperature of coke formation (400°C) resulted in higher intensities of EPR spectra, whereas higher temperature of alumina calcination (800°C), prior to its use in alcohol decomposition reaction, brought about lower spectral intensities.