Thermal analysis (TG-DTA) and drift spectroscopy applied to investigate the evolution of humic acids in forest soil at different vegetation stages

Humic acids (HAs) extracted from soils developed under two Norwegian spruce (Picea abies, (L.) Karst) subalpine forests of northern Italy were characterized using chemical, thermal (TG-DTA) and spectroscopic (DRIFT) analyses. The samples were taken from five sites which differed in orientation (northern and southern exposure) and vegetal cover at different old age: grassland, regeneration, immature and mature stands. In general, the thermal patterns of HAs were similar (three exothermic reactions appeared around at 300, 400 and 500°C) in both sites in grasslands and regeneration while a considerable modification appeared in HA from stands of different age at northern and southern exposure site. DRIFT spectroscopy confirmed the differences observed through TG-DTA analysis. In particular the main structural changes were ascribed to modification of carbonyl group and of CH stretching in aliphatic components in each HAs from different sites.     

Exponentially long time stability near an equilibrium point for non–linearizable analytic vector fields

We study the orbit behaviour of a germ of an analytic vector field of We prove that if its linear part is semisimple, non–resonant and verifies a Bruno–like condition, then the origin is effectively stable: stable for finite but exponentially long times.Received: July 5, 2004; revised: December 9, 2004     

Aging of cholinesterases phosphylated by tabun proceeds through O-dealkylation

Human butyrylcholinesterase (hBChE) hydrolyzes or scavenges a wide range of toxic esters, including heroin, cocaine, carbamate pesticides, organophosphorus pesticides, and nerve agents. Organophosphates (OPs) exert their acute toxicity through inhibition of acetylcholinesterase (AChE) by phosphorylation of the catalytic serine. Phosphylated cholinesterase (ChE) can undergo a spontaneous, time-dependent process called "aging", during which the OP-ChE conjugate is dealkylated. This leads to irreversible inhibition of the enzyme. The inhibition of ChEs by tabun and the subsequent aging reaction are of particular interest, because tabun-ChE conjugates display an extraordinary resistance toward most current oxime reactivators. We investigated the structural basis of oxime resistance for phosphoramidated ChE conjugates by determining the crystal structures of the non-aged and aged forms of hBChE inhibited by tabun, and by updating the refinement of non-aged and aged tabun-inhibited mouse AChE (mAChE). Structures for non-aged and aged tabun-hBChE were refined to 2.3 and 2.1 A, respectively. The refined structures of aged ChE conjugates clearly show that the aging reaction proceeds through O-dealkylation of the P(R) enantiomer of tabun. After dealkylation, the negatively charged oxygen forms a strong salt bridge with protonated His438N epsilon2 that prevents reactivation. Mass spectrometric analysis of the aged tabun-inhibited hBChE showed that both the dimethylamine and ethoxy side chains were missing from the phosphorus. Loss of the ethoxy is consistent with the crystallography results. Loss of the dimethylamine is consistent with acid-catalyzed deamidation during the preparation of the aged adduct for mass spectrometry. The reported 3D data will help in the design of new oximes capable of reactivating tabun-ChE conjugates.     

Measuring velocity of speckle fields with digital speckle pattern interferometry

We investigate a digital method for detecting the velocity of a diffusing object. The technique is based on Digital Speckle Pattern Interferometry (DSPI). A set of reference fringes is generated externally through the reference beam in a digital interferometer. As the object moves, subsequent frames are acquired and subtracted according to the normal DSPI procedure and stored. By means of the theory of first order speckle statistics applied to speckle intensity correlation, we relate the visibility variations in the reference fringes with the object velocity. Thus, by measuring the fringe visibility variation in the resulting DSPI stored frames the mean object velocity can be obtained. The theoretical results are experimentally verified.     

Engineered biosynthesis of hybrid macrolide polyketides containing D-angolosamine and D-mycaminose moieties

The glycosylation of natural product scaffolds with highly modified deoxysugars is often essential for their biological activity, being responsible for specific contacts to molecular targets and significantly affecting their pharmacokinetic properties. In order to provide tools for the targeted alteration of natural product glycosylation patterns, significant strides have been made to understand the biosynthesis of activated deoxysugars and their transfer. We report here efforts towards the production of plasmid-borne biosynthetic gene cassettes capable of producing TDP-activated forms of D-mycaminose, D-angolosamine and D-desosamine. We additionally describe the transfer of these deoxysugars to macrolide aglycones using the glycosyl transferases EryCIII, TylMII and AngMII, which display usefully broad substrate tolerance.     

Quantum computation with programmable connections between gates

A new model of quantum computation is considered, in which the connections between gates are programmed by the state of a quantum register. This new model of computation is shown to be more powerful than the usual quantum computation, e.g. in achieving the programmability of permutations of N different unitary channels with 1 use instead of N uses per channel. For this task, a new elemental resource is needed, the quantum switch, which can be programmed to switch the order of two channels with a single use of each one.     

Open tubular liquid chromatography: Recent advances and future trends

Nano-liquid chromatography (nanoLC) is gaining significant attention as a primary analytical technique across various scientific domains. Unlike conventional high-performance LC, nanoLC utilizes columns with inner diameters (i.ds.) usually ranging from 10 to 150 μm and operates at mobile phase flow rates between 10 and 1000 nl/min, offering improved chromatographic performance and detectability. Currently, most exploration of nanoLC has focused on particle-packed columns. Although open tubular LC (OTLC) can provide superior performance, optimized OTLC columns require very narrow i.ds. (< 10 μm) and demand challenging instrumentation. At the moment, these challenges have limited the success of OTLC. Nevertheless, remarkable progress has been made in developing and utilizing OTLC systems featuring narrow columns (< 2 μm). Additionally, significant efforts have been made to explore larger columns (10–75 μm i.d), demonstrating practical applicability in many situations. Due to their perceived advantages, interest in OTLC has resurged in the last two decades. This review provides an updated outlook on the latest developments in OTLC, focusing on instrumental challenges, achievements, and advancements in column technology. Moreover, it outlines selected applications that illustrate the potential of OTLC for performing targeted and untargeted studies.