[Physical Basis of Functioning of Antifreeze Protein].

Antifreeze proteins, expressed in cold-blooded organisms, prevent ice formation in their bodies, and thus help them to survive in extremely cold winter temperatures. However, the mechanism of action of these proteins is still not clear. In any case, it is not simply a decrease in the temperature of normal ice formation. In this work, investigating the ice-binding protein (a mutant form of the antifreeze protein cfAFP from the spruce budworm Choristoneura fumiferana, which overwinters in needles), we showed that this antifreeze protein does not at all lower the freezing point of water and, paradoxically, increases the melting point of ice. On the other hand, calculations based on the theory of crystallization show that at temperatures of 0° to -30°C ice can only appear on surfaces that contact water, but not in the body of water. These facts suggest a new perspective on the role of antifreeze proteins: their task is not (as it is commonly believed) to bind with nascent ice crystals already formed in the organism and stop their growth, but to bind to those surfaces, on which ice nuclei can appear, and thus completely inhibit the ice formation in supercooled water or biological fluid.

[Protein Biosynthesis Proofreading Is Closely Associated with the Existence of Factor-Free Ribosomal Synthesis].

Despite protein biosynthesis being studied for decades, some major questions concerning this process are still to be addressed. We elucidate a close connection between proofreading of the emerging amino acid sequence during its normal, elongation factor-dependent ribosomal biosynthesis and the existence of the factor-free synthesis of a polypeptide chain on a ribosome. In this factor-free process, the biological role of proofreading is played by a process opposite to the factor-free attachment of Aa-tRNA to the ribosome, namely, the removal via the same pathway of that Aa-tRNA, which is not complementary to the mRNA codon exhibited by the ribosome.

The validity of an experiment testing the influence of acceleration on time dilation using a rotating Mössbauer absorber and a Synchrotron Mössbauer Source.

Three experiments are reviewed, performed (in 2014-2016) at ID18 of ESRF to measure the influence of acceleration on time dilation by measuring the relative shift between the absorption lines of two states of the same rotating absorber with accelerations anti-parallel and parallel to the incident beam. Statistically significant data for rotation frequencies up to 510 Hz in both directions of rotation were collected. For each run with high rotation, a stable statistically significant `vibration-free' relative shift between the absorption lines of the two states was measured. This may indicate the influence of acceleration on time dilation. However, the measured relative shift was also affected by the use of a slit necessary to focus the beam to the axis of rotation to a focal spot of sub-micrometre size. The introduction of the slit broke the symmetry in the absorption lines due to the nuclear lighthouse effect and affected the measured relative shift, preventing to claim conclusively the influence of acceleration on time dilation. Assuming that this loss of symmetry is of first order, the zero value of the relative shift, corrected for this loss, falls always within the experimental error limits, as predicted by Einstein's clock hypothesis. The requirements and an indispensable plan for a conclusive experiment, once the improved technology becomes available, is presented. This will be useful to future experimentalists wishing to pursue this experiment or a related rotor experiment involving a Mössbauer absorber and a synchrotron Mössbauer source.

Correlates of burnout among professionals working with people with intellectual and developmental disabilities.

BACKGROUND: Although burnout has been recognised as an important stress-related problem among staff working with people with intellectual and developmental disabilities (IDD), literature on the subject is limited yet emerging. The aim of this study is twofold: (1) to evaluate the level of burnout within different professions working with IDD; (2) to examine the association between socio-demographic, professional and organisational characteristics and burnout. METHOD: One hundred ninety-nine professionals working with people with IDD were enrolled in the study (66% response rate). Participants were recruited from several facilities that provide care for people with IDD of all ages, in the Jerusalem area and in other cities in central Israel. The anonymous questionnaires included valid and reliable measures of burnout, socio-demographic variables, professional variables and organisational variables. RESULTS: Participants' mean age was 38.3 years, and most were women. There were no significant differences in burnout levels among the different professionals. Role ambiguity, perceived overload, care-recipient group and job involvement were significant predictors of burnout. The model explained a high percentage (46.8%) of the observed variance. CONCLUSIONS: Most of these predictors are organisational measures. These findings demonstrate that organisational variables are more significantly associated with burnout of staff working with people with IDD than the socio-demographic factors or professional characteristics. Identifying and better understanding the specific factors associated with burnout among professionals working with IDD could facilitate unique intervention programs to reduce burnout levels in staff.

50+ Years of Protein Folding.

The ability of proteins to spontaneously form their spatial structures is a long-standing puzzle in molecular biology. Experimentally measured rates of spontaneous folding of single-domain globular proteins range from microseconds to hours: the difference - 10-11 orders of magnitude - is the same as between the lifespan of a mosquito and the age of the Universe. This review (based on the literature and some personal recollections) describes a winding road to understanding spontaneous folding of protein structure. The main attention is given to the free-energy landscape of conformations of a protein chain - especially to the barrier separating its unfolded (U) and the natively folded (N) states - and to physical theories of rates of crossing this barrier in both directions: from U to N, and from N to U. It is shown that theories of both these processes come to essentially the same result and outline the observed range of folding and unfolding rates for single-domain globular proteins. In addition, they predict the maximal size of protein domains that fold under solely thermodynamic (rather than kinetic) control, and explain the observed maximal size of "foldable" protein domains.

The Molten Globule Concept: 45 Years Later.

In this review, we describe traditional systems where the molten globule (MG) state has been detected and give a brief description of the solution of Levinthal's paradox. We discuss new results obtained for MG-mediated folding of "nontraditional" proteins and a possible functional role of the MG. We also report new data on the MG, especially the dry molten globule.

[Evaluation of the Accuracy of Calculation of the Standard Binding Entropy of Molecules from their Average Mobility in Molecular Crystals].

One of the main problems in attempts to predict the binding constants of molecules (or free energies of their binding) is the correct evaluation of configurational binding entropy. This evaluation is possible by methods of molecular dynamics simulation, but these simulations require a lot of computational time. Earlier, we have developed an alternative approach which allows the fast calculation of the binding entropy from summarizing the available data on sublimation of crystals. Our method is based on evaluating the mean amplitude of the movements that are restricted in the bound molecule, e.g., in a crystal, but are not restricted in the free state, e.g., in vapor. In this work, it is shown that the standard entropy of binding of molecules by crystals under standard conditions (1 atm, 25°C) can be assessed rather accurately from geometric and physical parameters of the molecule and the average amplitude of the molecule motions in crystals estimated in our previous work.

[Anomalous Kinetics of Amyloidogenesis Suggest a Competition between Oligomers and Fibrils].

Meisl et al. have recently observed an anomalous dependence of the amyloid formation rate on the protein concentration. A novel mechanism of fibril growth has been proposed by Meisl et al. to explain the abnormality; it consists in the fibril-catalyzed initiation of fibril formation with saturation of catalytic sites at high concentrations of substrates. Our article describes an alternative explanation of the anomalous kinetics, assuming that the formation of metastable oligomers competes with fibril formation by decreasing the concentration of free monomers. Oligomers are indeed observed in the course of amyloid formation, but are usually considered as seeds of amyloid fibrils rather as their competitors. However, the oligomers visually detectable by electron microscopy were shown to be close in size to those that can be derived from the anomalous dependence of the amyloid growth rate on the protein concentration, given that the anomaly results from competition between oligomer formation and amyloidogenesis.

[Intersubunit Mobility of the Ribosome].

Ribosomes are ribonucleoprotein nanoparticles synthesizing all proteins in living cells. The function of the ribosome is to translate the genetic information encoded in a nucleotide sequence of mRNA into the amino acid sequence of a protein. Each translation step (occurring after the codon-dependent binding of the aminoacyl-tRNA with the ribosome and mRNA) includes (i) the transpeptidation reaction and (ii) the translocation that unidirectionally drives the mRNA chain and mRNA-bound tRNA molecules through the ribosomal intersubunit space; the latter process is driven by the free energy of the chemical reaction of transpeptidation. Thus, the translating ribosome can be considered a conveying protein-synthesizing molecular machine. In this review we analyze the role of ribosomal intersubunit mobility in the process of translocation.

Intermediate States of Apomyoglobin: Are They Parts of the Same Area of Conformations Diagram?

Several research teams have reported detection and characterization of various apomyoglobin intermediate states different in their accumulation mode, thus putting a natural question as to proportions of these intermediates. The current report presents spectral properties of sperm whale apomyoglobin studied over a wide range of conditions with the use of circular dichroism and fluorescence techniques. Based on the experimental data, a diagram of apomyoglobin conformational states has been constructed. It shows that though induced by various denaturants, all the observed intermediates belong to one and the same area in the diagram.

Physicians' communication styles as correlates of elderly cancer patients' satisfaction with their doctors.

Physician-patient communication style is of utmost importance to patients with life-threatening diseases. This study identifies the most desired physician communication style by older cancer patients; and examines which of the studied communication styles significantly explains cancer patients' satisfaction with family physicians. A total of 200 older cancer patients, with average age of 75 years, participated in the study, yielding a response rate of 42%. Prospective respondents were randomly selected from the list of cancer patients in the central geographical district of Israel's second largest Health Maintenance Organization fund. Respondents rated their satisfaction with physicians as relatively high. All three communication styles studied were found to be associated with patient's satisfaction. Associations were found between self-rated health, time since the diagnosis of cancer and satisfaction. Women were less satisfied than men with their physicians. Two variables emerged as significant predictors of satisfaction: the physician's caring communication style and patient's gender. Intervention programmes should focus on elevating physicians' awareness of the importance of their communication with cancer patients in general, and of the caring communication style in particular.

[Calculation of mobility and entropy of the binding of molecules by crystals].

A simple method for evaluating a range of molecular movements in crystals has been developed. This estimate is needed to calculate the entropy of binding, in particular in protein-ligand complexes. The estimate is based on experimental data concerning the enthalpy of sublimation and saturated vapor pressure obtained for 15 organic crystals with melting temperatures of 25-80°Ð¡. For this set, we calculated the values of the average range and the corresponding average amplitude of molecular movements in crystals that constituted 0.75 ± 0.14 Å and 0.18 ± 0.03 Å, respectively. The entropy of sublimation calculated based on the average range of molecular movements in crystals was well consistent with the experimental data.

Prevalence of blood type A and risk of vascular complications following transcatheter aortic valve implantation.

OBJECTIVES: To assess the prevalence of blood type A among patients referred for transcatheter aortic valve implantation (TAVI) and whether it is related to vascular complications. BACKGROUNDS: Vascular complications following TAVI are associated with adverse outcomes. Various blood types, particularly type A, have been shown to be more prevalent in cardiovascular diseases and to be related to prognosis. METHODS: The prevalence of various blood types in a cohort of 491 consecutive patients who underwent TAVI was compared with a control group of 6500 consecutive hospitalised patients. The prevalence and predictors of vascular complications and bleeding events were evaluated in the blood type A group and were compared with non-type A patients. RESULTS: The mean age of TAVI patients was 83 ± 6 years, and 40 % were males. Patients were divided into two groups: blood type A (n = 220) and non-type A (n = 271). Type A was significantly more prevalent in the TAVI group than in the control group (45 vs. 38 %, p = 0.023). Compared with the non-type A group, patients with blood type A had more major and fatal bleeding (14.5 vs. 8.1 %, p = 0.027) and more vascular complications (any vascular complication: 24.5 vs. 15.9 % p = 0.016; major vascular complications: 12.3 vs. 7 % p = 0.047). In a multivariable analysis, blood type A emerged as a significant and independent predictor for vascular complications and bleeding events. CONCLUSIONS: Blood type A is significantly more prevalent in TAVI patients than in the general population and is related to higher rates of vascular and bleeding complications.

Using a Systems Pharmacology Approach to Study the Effect of Statins on the Early Stage of Atherosclerosis in Humans.

More than 100,000 people have participated in controlled trials of statins (lowering cholesterol drugs) since the introduction of lovastatin in the 1980s. Meta-analyses of this data have shown that statins have a beneficial effect on treated groups compared to control groups, reducing cardiovascular risk. Inhibiting the HMG-CoA reductase in the liver, statins can reduce cholesterol levels, thus reducing LDL levels in circulation. Published data from intravascular ultrasound studies (IVUS) was used in this work to develop and validate a unique integrative system model; this consisted of analyzing control groups from two randomized controlled statins trials (24/97 subjects respectively), one treated group (40 subjects, simvastatin trial), and 27 male subjects (simvastatin, pharmacokinetic study). The model allows to simulate the pharmacokinetics of statins and its effect on the dynamics of lipoproteins (e.g., LDL) and the inflammatory pathway while simultaneously exploring the effect of flow-related variables (e.g., wall shear stress) on atherosclerosis progression.

Synchrotron radiation Mössbauer spectra of a rotating absorber with implications for testing velocity and acceleration time dilation.

Many Mössbauer spectroscopy (MS) experiments have used a rotating absorber in order to measure the second-order transverse Doppler (TD) shift, and to test the validity of the Einstein time dilation theory. From these experiments, one may also test the clock hypothesis (CH) and the time dilation caused by acceleration. In such experiments the absorption curves must be obtained, since it cannot be assumed that there is no broadening of the curve during the rotation. For technical reasons, it is very complicated to keep the balance of a fast rotating disk if there are moving parts on it. Thus, the Mössbauer source on a transducer should be outside the disk. Friedman and Nowik have already predicted that the X-ray beam finite size dramatically affects the MS absorption line and causes its broadening. We provide here explicit formulas to evaluate this broadening for a synchrotron Mössbauer source (SMS) beam. The broadening is linearly proportional to the rotation frequency and to the SMS beam width at the rotation axis. In addition, it is shown that the TD shift and the MS line broadening are affected by an additional factor assigned as the alignment shift which is proportional to the frequency of rotation and to the distance between the X-ray beam center and the rotation axis. This new shift helps to align the disk's axis of rotation to the X-ray beam's center. To minimize the broadening, one must focus the X-ray on the axis of the rotating disk and/or to add a slit positioned at the center, to block the rays distant from the rotation axis of the disk. Our experiment, using the (57)Fe SMS, currently available at the Nuclear Resonance beamline (ID18) at the ESRF, with a rotating stainless steel foil, confirmed our predictions. With a slit installed at the rotation axis (reducing the effective beam width from 15.6 µm to 5.4 µm), one can measure a statistically meaningful absorption spectrum up to 300 Hz, while, without a slit, such spectra could be obtained up to 100 Hz only. Thus, both the broadening and the alignment shift are very significant and must be taken into consideration in any rotating absorber experiment. Here a method is offered to measure accurately the TD shift and to test the CH.

A composite computational model of liver glucose homeostasis. II. Exploring system behaviour.

Using a composite model of the glucose homeostasis system, consisting of seven interconnected submodels, we enumerate the possible behaviours of the model in response to variation of liver insulin sensitivity and dietary glucose variability. The model can reproduce published experimental manipulations of the glucose homeostasis system and clearly illustrates several important properties of glucose homeostasis-boundedness in model parameters of the region of efficient homeostasis, existence of an insulin sensitivity that allows effective homeostatic control and the importance of transient and oscillatory behaviour in characterizing homeostatic failure. Bifurcation analysis shows that the appearance of a stable limit cycle can be identified.

A composite computational model of liver glucose homeostasis. I. Building the composite model.

A computational model of the glucagon/insulin-driven liver glucohomeostasis function, focusing on the buffering of glucose into glycogen, has been developed. The model exemplifies an 'engineering' approach to modelling in systems biology, and was produced by linking together seven component models of separate aspects of the physiology. The component models use a variety of modelling paradigms and degrees of simplification. Model parameters were determined by an iterative hybrid of fitting to high-scale physiological data, and determination from small-scale in vitro experiments or molecular biological techniques. The component models were not originally designed for inclusion within such a composite model, but were integrated, with modification, using our published modelling software and computational frameworks. This approach facilitates the development of large and complex composite models, although, inevitably, some compromises must be made when composing the individual models. Composite models of this form have not previously been demonstrated.

Increased erythrocyte aggregation in men with coronary artery disease and erectile dysfunction.

We studied the association between erythrocyte aggregation (EA) and erectile dysfunction (ED) in men with coronary artery disease (CAD). Men with CAD documented by coronary angiography filled the Sexual Health Inventory for Males questionnaire to detect ED and assess its severity. EA was evaluated by filming slides of blood smear. Low percentage of slide field covered by erythrocytes represented increased EA. Overall, 133 men with CAD, mean ages 62.4+/-12.2 years, were included: 100 (75.2%) with ED and 33 (24.8%) without ED. EA was increased among men with ED compared with men without ED (percentage of slide field covered by erythrocytes 66.7+/-14.7 vs 73.1+/-14.5%; P=0.03). After adjustment for age, diabetes mellitus, hemoglobin and hematocrit levels, EA was associated with ED severity (r=0.18; P=0.038). We conclude that EA is increased in men with CAD and ED. This finding may be relevant to the pathophysiology of ED in men with CAD.

Pedestrian and pedalcyclist injury costs in the United States by age and injury severity.

This paper estimates the incidence, unit costs, and annual costs of pedestrian and pedalcycle crash injuries in the United States. It includes medical care costs, household and wage work losses, and the value of pain, suffering, and lost quality of life. The estimates are broken down by body region and severity. They rely heavily on data from the health care system. Costs of pedestrian and pedalcycle injuries in 2000 will total 40 billion dollars over the lifetimes of the injured. Most pedalcyclist injury costs and half of pedestrian injury costs do not involve motor vehicles. Youth ages 5-14 face greater annual risks when walking or driving their own pedaled vehicles than when being driven. Children under age 5 experience higher costs than their elders when injured as pedestrians. Our results suggest European and Japanese component tests used to design pedestrian injury countermeasures for motor vehicles are too narrow. Separate lower limb testing is needed for younger children. Testing for torso/vertebral column injury of adults also seems desirable.