Extracting hydrophobicity parameters from solute partition and protein mutation/unfolding experiments

Hydrophobicity values for amino acids obtained from proteinunfolding experiments are about twice as large as those obtainedfrom data on the partitioning of amino acids between water andoctanol. Quantitative analyses of several data sets, presentedhere, indicate that the difference is best explained by themost direct hypothesis, i.e. that the environment of hydrophobicgroups in the interior of a protein is poorly modeled by octanol.Instead, we propose—and provide supporting evidence—thathydrocarbons are a more suitable model. First, we reanalyzedata from both solute partitioning and protein unfolding experiments,taking account of the effects that were omitted previously,by introducing a volume dependence in the former and a fullfree energy analysis in the latter. Both changes in evaluationmethodology decrease the discrepancy, but the differences remainsubstantial. The hydrophobicity parameter obtained from side–chaintransfers between octanol and water increases from 16.7 to 22cal/ mol/², while that obtained from protein unfolding decreasesfrom 34.9 to 31.2 cal/mol/². On the other hand,our analysisof the solubilities of pure hydrocarbons in water provides ahydrophobicity parameter of 30.8 cal/mol/². This apparent hydrocarbon–likeenvironment of a protein's interior is also suggested more directlyby an analysis of the contact environment of hydrophobic sidechains in mutation/unfolding experiments, which have polar contactareas that are     

Thermal modelling of the high temperature treatment of wood based on Luikov's approach

A 3D, unsteady‐state mathematical model was used to simulate the behaviour of wood during high temperature treatment. The model is based on Luikov's approach and solves a set of coupled heat and mass transfer equations. Using the model, the temperature and moisture content profiles of wood were predicted as a function of time for different heating rates. Parallel to the modelling study, an experimental study was carried out using small birch samples. The samples were subjected to high temperature treatment in a thermogravimetric system under different operating conditions. The experimental results and the model predictions were found to be in good agreement. The results show that the distributions of temperature and moisture content are influenced appreciably by the heating rate and the initial moisture content. Copyright © 2005 John Wiley & Sons, Ltd.     

Optimization of four-bar function generating mechanisms using penalty functions with inequality and equality constraints

This paper demonstrates the application of the penalty function technique to the optimal kinematic synthesis of mechanisms, and presents a new method of finding feasible initial approximations for the mechanism parameters. The procedure is demonstrated by an example.     

The mechanism involved in the central effect of 5-leu enkephalin on the calcitonin secretion

Calcitonin (CT) secretion is not exclusively under the control of calcium levels in the plasma, but also depends on the sympathetic-adrenergic tone. In previous experiments we stressed out the possible role played by 5-leu enkephalin (5-LE) in the nervous regulation of the CT secretion. Intracerebroventricular (i.c.v.) 5-LE in doses of 100 micrograms could act at a central level through a mechanism independent from the noradrenergic pathways, since i.c.v. 6-OHDA and propranolol could not interfere with its stimulatory effect on the CT content of the thyroid. In the present experiments, performed in anaesthetized Wistar-Bratislava rats, we studied the involvement of mu and delta receptors in the central effect of 5-LE on the CT content of the thyroids and the CT levels in the plasma. These parameters were measured in parallel, by means of a competitive radioimmunoassay with double antibodies (Peninsula Lab.). 5-LE probably bound to both mu and delta receptors, since its effect on the CT secretion was reversed by 13 micrograms of naloxone (i.c.v.). A partial blockade, comparable to naloxone, was noticed after 382 micrograms of CTOP (i.c.v.), a specific antagonist of the mu receptors--stressing out their involvement in the stimulatory effect of 5-LE on the CT secretion. 250 Ug of ICI 174864 (i.c.v.), a selective antagonist the the delta receptors completely blocked the stimulation induced by 5-LE on the CT secretion to values significantly lower as compared to the controls and even to the sympathectomized group. This suggests the tonic role played by enkephalins in the CT secretion, through the central activation of delta receptors.(ABSTRACT TRUNCATED AT 250 WORDS)     

State stabilization for gate-model quantum computers

Quantum Information Processing - Historically, the information efficiency of the secret key in quantum key distribution (QKD) schemes based on binary signal formats was limited to 1 bit/particle....     

Nanomotion Detection Method for Testing Antibiotic Resistance and Susceptibility of Slow‐Growing Bacteria

Infectious diseases are caused by pathogenic microorganisms and are often severe. Time to fully characterize an infectious agent after sampling and to find the right antibiotic and dose are important factors in the overall success of a patient's treatment. Previous results suggest that a nanomotion detection method could be a convenient tool for reducing antibiotic sensitivity characterization time to several hours. Here, the application of the method for slow‐growing bacteria is demonstrated, taking Bordetella pertussis strains as a model. A low‐cost nanomotion device is able to characterize B. pertussis sensitivity against specific antibiotics within several hours, instead of days, as it is still the case with conventional growth‐based techniques. It can discriminate between resistant and susceptible B. pertussis strains, based on the changes of the sensor's signal before and after the antibiotic addition. Furthermore, minimum inhibitory and bactericidal concentrations of clinically applied antibiotics are compared using both techniques and the suggested similarity is discussed.     

Kinematic analysis of three-link spatial mechanisms containing sphere-plane and sphere-groove pairsAnalyse cinématique des mécanismes spatiaux a trois barres contenant les paires sphère-plan et sphère-rainure

Kinematic pairs in a spatial mechanism are viewed either as allowing relative screw motion between links or as constraining the motion of the two chains of the mechanism connected to the two elements of the pair. Using pair geometry constraints of the sphere-plane and sphere-groove kinematic pairs, the displacement, velocity and accelerations equations are derived for, R-Sp-R, 5 R-Sp-P, P-Sp-P, P-Sp-R and R-Sg-C three-link mechanisms. For known values of the input variable, other variables are computed in closed form. The analysis procedures are illustrated using numerical examples.