From Isotropic to Anisotropic Side Chain Representations: Comparison of Three Models for Residue Contact Estimation

The criterion to determine residue contact is a fundamental problem in deriving knowledge-based mean-force potential energy calculations for protein structures. A frequently used criterion is to require the side chain center-to-center distance or the -to- atom distance to be within a pre-determined cutoff distance. However, the spatially anisotropic nature of the side chain determines that it is challenging to identify the contact pairs. This study compares three side chain contact models: the Atom Distance criteria (ADC) model, the Isotropic Sphere Side chain (ISS) model and the Anisotropic Ellipsoid Side chain (AES) model using 424 high resolution protein structures in the Protein Data Bank. The results indicate that the ADC model is the most accurate and ISS is the worst. The AES model eliminates about 95% of the incorrectly counted contact-pairs in the ISS model. Algorithm analysis shows that AES model is the most computational intensive while ADC model has moderate computational cost. We derived a dataset of the mis-estimated contact pairs by AES model. The most misjudged pairs are Arg-Glu, Arg-Asp and Arg-Tyr. Such a dataset can be useful for developing the improved AES model by incorporating the pair-specific information for the cutoff distance

Synergism between particle-based multiplexing and microfluidics technologies may bring diagnostics closer to the patient

In the field of medical diagnostics there is a growing need for inexpensive, accurate, and quick high-throughput assays. On the one hand, recent progress in microfluidics technologies is expected to strongly support the development of miniaturized analytical devices, which will speed up (bio)analytical assays. On the other hand, a higher throughput can be obtained by the simultaneous screening of one sample for multiple targets (multiplexing) by means of encoded particle-based assays. Multiplexing at the macro level is now common in research labs and is expected to become part of clinical diagnostics. This review aims to debate on the “added value” we can expect from (bio)analysis with particles in microfluidic devices. Technologies to (a) decode, (b) analyze, and (c) manipulate the particles are described. Special emphasis is placed on the challenges of integrating currently existing detection platforms for encoded microparticles into microdevices and on promising microtechnologies that could be used to down-scale the detection units in order to obtain compact miniaturized particle-based multiplexing platforms

Quasiliving Carbocationic Polymerization. Xi: an Interpretation of Solvent Effects by Donor and Acceptor Numbers

Counteranion/solvent interactions (counteranion solvation) profoundly influence each and every elementary step of carbocationic polymerizations and are just as important as the commonly emphasized cation/solvent interactions (cation solvation). Counteranion solvation and carbocation solvation have been characterized by Gutmann\u27 s acceptor number AN and donor number DN, respectively. Analysis of earlier data leads to the conclusion that the effect of monomer concentration on the rate, molecular weight, and molecular weight distribution obtained in cationic olefin polymerizations in “polar” solvents are in fact due to subtle changes in solvent concentration. Indeed, olefin monomers behave as “nonpolar” solvents and by changing the monomer concentration the character of the medium may profoundly change. It is further concluded that quasiliving polymerizations cannot be achieved in batch operations because the conditions that prevail in the initial charge, although possibly suitable for quasiliving polymerizations, must continuously change with the diminishing monomer concentration, i.e., by continuously changing the solvent character of the system. In contrast, in continuous systems initial conditions in the charge suitable for the attainment of living or quasiliving conditions can be maintained even for long periods of time by continuously replenishing the consumed monomer. By the use of these concepts, heretofore unexplained observations made in the course of quasiliving polymerization studies have been accounted for and, beyond this, new insight into solvation phenomena in cationic polymerizations is generated

Quasiliving Carbocationic Polymerization V: Quasiliving Polymerization of Lndene

Quasiliving polymerization of indene, i.e., an increase of the molecular weight of polyindenes with the cumulative amount of consumed monomer, has been demonstrated using the “H2O”/ BCl3, 2-chloroindene/BCl, “H2O”/TiCl4, 2-chloroindene/TiCl4, and cumyl chloride/TiCl4 initiating systems in CH2Cl2solvent at -50°C. However, chain transfer operates in every system investigated, and sets a limit to DPn,max. The efficiency of the 2-chloroindene and cumyl chloride initiators is very low. The behavior of BCl3and TiCl4 coinitiators on the polymerization has also been investigated

Hypoglycemia as a Symptom of Neoplastic Disease, with a focus on Insulin-like Growth Factors Producing Tumors

Abstract View references (38) This article reviews the current knowledge of uncommon causes of hypoglycemia, with a focus on neoplastic disease. However, these situations are rare. They commonly accompany severely ill patients and therefore a proper diagnosis is the basis for relevant treatment. Here we discuss the pathophysiological foundation of hypoglycemia \u2013 situations caused by increased insulin production or sensitivity \u2013 but we also focus on different cytokines which could cause hypoglycemia, especially IGF-II production in what are called nonislet cell tumors. From the clinical perspective we can divide the patients who are affected into "seemingly ill\u201d or \u201chealthy patients\u201d and lead the diagnostic process accordingly. \ua9 The author(s)

Optimization of the rotational moulding process for polyolefins

Hollow plastic parts can be made by a number of manufacturing methods, but only rotational moulding offers the ability to create one-piece, stress-free parts with attractive economics. However, the fundamental nature of rotational moulding is such that cycle times are long. Consequently, the plastic is subjected to relatively high temperatures, in the presence of air, for excessive periods of time. This can lead to thermal and oxidative degradation at the inner free surface of the plastic, resulting in a deterioration in the performance of the moulded part. The industry relies heavily on the experience of operators to establish the best processing conditions to avoid degradation, but this is problematic and inefficient. Unfortunately, automatic process control is difficult owing to the complex rotation of the mould. Recent developments highlighting the importance of the peak air temperature inside the mould have been an important step forward, but ever-increasing technical demands on moulders make it clear that more sophisticated process control is needed. It is known that the processing conditions that lead to degradation vary with factors that affect the heating rate, such as the type of mould used and the thickness of the end-product. In the work reported here, a method is proposed for predicting the onset of degradation, on the basis that this occurs when the concentration of antioxidant in the polymer reaches zero. Good agreement has been obtained between the experimental and predicted optimum processing temperature for polyethylenes stabilized with different antioxidant systems. A procedure is described for identifying the best rotational moulding conditions so that more efficient manufacturing methods can be achieved