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How an established behavior is retained and consistently produced by a nervous system in constant flux remains a mystery. One possible solution to ensure long-term stability in motor output is to fix the activity patterns of single neurons in the relevant circuits. Alternatively, activity in single cells could drift over time provided that the population dynamics are constrained to produce the same behavior. To arbitrate between these possibilities, we recorded single-unit activity in motor cortex and striatum continuously for several weeks as rats performed stereotyped motor behaviors—both learned and innate. We found long-term stability in single neuron activity patterns across both brain regions. A small amount of drift in neural activity, observed over weeks of recording, could be explained by concomitant changes in task-irrelevant aspects of the behavior. These results suggest that long-term stable behaviors are generated by single neuron activity patterns that are themselves highly stable.

The basal ganglia are known to influence action selection and modulation of movement vigor, but whether and how they contribute to specifying the kinematics of learned motor skills is not understood. Here, we probe this question by recording and manipulating basal ganglia activity in rats trained to generate complex task-specific movement patterns with rich kinematic structure. We find that the sensorimotor arm of the basal ganglia circuit is crucial for generating the detailed movement patterns underlying the acquired motor skills. Furthermore, the neural representations in the striatum, and the control function they subserve, do not depend on inputs from the motor cortex. Taken together, these results extend our understanding of the basal ganglia by showing that they can specify and control the fine-grained details of learned motor skills through their interactions with lower-level motor circuits.

We studied the surface properties of Aβ(1–40) amyloid peptides mixed with 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) (liquid state) or 1,2-disteraoyl-phosphatidylcholine (DSPC) (solid state) phospholipids by using nanostructured lipid/peptide films (Langmuir monolayers). Pure Aβ(1–40) amyloid peptides form insoluble monolayers without forming fibril-like structures. In a lipid environment [phospholipid/Aβ(1–40) peptide mixtures], we observed that both miscibility and stability of the films depend on the peptide content. At low Aβ(1–40) amyloid peptide proportion (from 2.5 to 10% of peptide area proportion), we observed the formation of a fibril-like structure when mixed only with POPC lipids. The stability acquired by these mixed films is within 20–35 mN·m–1compatible with the equivalent surface pressure postulated for natural biomembranes. Fibrils are clearly evidenced directly from the monolayers by using Brewster angle microscopy. The so-called nanostructured fibrils are thioflavin T positive when observed by fluorescence microscopy. The amyloid fibril network at the surface was also evidenced by atomic force microscopy when the films are transferred onto a mica support. Aβ(1–40) amyloid mixed with the solid DSPC lipid showed an immiscible behavior in all peptide proportions without fibril formation. We postulated that the amyloid fibrillogenesis at the membrane can be dynamically nano-self-triggered at the surface by the quality of the interfacial environment, that is, the physical state of the water–lipid interface and the relative content of amyloid protein present at the interface.

AimsThere is a lack of long-term data for minimally invasive acromioclavicular (AC) joint repair. Furthermore, it is not clear if good early clinical results can be maintained over time. The purpose of this study was to report long-term results of minimally invasive AC joint reconstruction (MINAR) and compare it to corresponding short-term data.MethodsWe assessed patients with a follow-up of at least five years after minimally invasive flip-button repair for high-grade AC joint dislocation. The clinical outcome was evaluated using the Constant score and a questionnaire. Ultrasound determined the coracoclavicular (CC) distance. Results of the current follow-up were compared to the short-term results of the same cohort.ResultsA total of 50 patients (three females, 47 males) were successfully followed up for a minimum of five years. The mean follow-up was 7.7 years (63 months to 132 months). The overall Constant score was 94.4 points (54 to 100) versus 97.7 points (83 to 100) for the contralateral side showing a significant difference for the operated shoulder (p = 0.013) The mean difference in the CC distance between the operated and the contralateral shoulder was 3.7 mm (0.2 to 7.8; p = 0.010). In total, 16% (n = 8) of patients showed recurrent instability. All these cases were performed within the first 16 months after introduction of this technique. A total of 84% (n = 42) of the patients were able to return to their previous occupations and sport activities. Comparison of short-term and long-term results revealed no significant difference for the Constant Score (p = 0.348) and the CC distance (p = 0.974).ConclusionThe clinical outcome of MINAR is good to excellent after long-term follow-up and no significant differences were found compared to short-term results. We therefore suggest this is a reliable technique for surgical treatment of high-grade AC joint dislocation.Cite this article: Bone Joint J2020;102-B(7):918–924.

The European XFEL is a hard X-ray free-electron laser (FEL) based on a high-electron-energy superconducting linear accelerator. The superconducting technology allows for the acceleration of many electron bunches within one radio-frequency pulse of the accelerating voltage and, in turn, for the generation of a large number of hard X-ray pulses. We report on the performance of the European XFEL accelerator with up to 5,000 electron bunches per second and demonstrating a full energy of 17.5 GeV. Feedback mechanisms enable stabilization of the electron beam delivery at the FEL undulator in space and time. The measured FEL gain curve at 9.3 keV is in good agreement with predictions for saturated FEL radiation. Hard X-ray lasing was achieved between 7 keV and 14 keV with pulse energies of up to 2.0 mJ. Using the high repetition rate, an FEL beam with 6 W average power was created.

Background/Objective:Previous research has focused on associations between dietary fat and body mass index (BMI), but the contributions of different types of fat to BMI remain unclear. The purpose of this study is to estimate whether plasma phospholipid omega-3 (n-3), omega-6 (n-6) or trans fatty acids are associated with BMI at baseline and with subsequent BMI changes over time; and whether total phospholipid n-6 or trans fatty acids modify any association between phospholipid n-3 and BMI.Methods:Cross-sectional and longitudinal linear mixed models include 6243 participants in the Multi-Ethnic Study of Atherosclerosis (MESA) cohort. Participants were 45-84 years old, had no history of cardiovascular disease at baseline (2000-2002) and were followed for up to 10 years. Plasma phospholipid fatty acids were measured using fasting plasma samples at baseline. Fully adjusted models include demographics, health behaviors and other fatty acids (n-3, n-6 and trans) as appropriate.Results:In fully adjusted models, phospholipid n-3 fatty acid levels were inversely associated with baseline BMI (Ptrend<0.001). Baseline BMI was 1.14 (95% confidence interval (CI): 0.71, 1.57) kg?m–2lower among participants with total n-3 values in the highest vs the lowest quartiles, but was not associated with changes in BMI. Total phospholipid n-6 was positively associated with baseline BMI in partially adjusted but not fully adjusted models. No overall association was observed between fatty acid levels and changes in BMI. No clear association was observed between trans fatty acids and baseline BMI or BMI change. No effect modification in the association between phospholipid n-3 and baseline BMI or BMI change was observed by either phospholipid n-6 or trans fatty acids.Conclusions:Phospholipid total and specific n-3 fatty acid levels were inversely associated with BMI at baseline, whereas associations tended to be positive for total n-6 fatty acids. Significant associations between fatty acid levels and BMI changes were not observed.

Cracks, formed during the drying of particulate films, can reduce the effectiveness or even render products useless. We present a novel, generic approach to suppress crack formation in thin films made from hard particle suspensions, which are otherwise highly susceptible to cracking, using the capillary force between particles present when a trace amount of an immiscible liquid is added to a suspension. This secondary liquid preserves the particle cohesion, modifying the structure and increasing the drying rate. Crack-free films can be produced at thicknesses much greater than the critical cracking thickness for a suspension without capillary interactions, and even persists after sintering. This capillary suspension strategy is applicable to a broad range of materials, including suspensions of metals, semiconductive and ceramic oxides, or glassy polymeric particles, and can be easily implemented in many industrial processes since it is based on well-established unit operations. Promising fields of application include ceramic foils and printed electronic devices.

Survival in threatening situations depends on the selection and rapid execution of an appropriate active or passive defensive response, yet the underlying brain circuitry is not understood. Here we use circuit-based optogenetic, in vivoand in vitroelectrophysiological, and neuroanatomical tracing methods to define midbrain periaqueductal grey circuits for specific defensive behaviours. We identify an inhibitory pathway from the central nucleus of the amygdala to the ventrolateral periaqueductal grey that produces freezing by disinhibition of ventrolateral periaqueductal grey excitatory outputs to pre-motor targets in the magnocellular nucleus of the medulla. In addition, we provide evidence for anatomical and functional interaction of this freezing pathway with long-range and local circuits mediating flight. Our data define the neuronal circuitry underlying the execution of freezing, an evolutionarily conserved defensive behaviour, which is expressed by many species including fish, rodents and primates. In humans, dysregulation of this ‘survival circuit’ has been implicated in anxiety-related disorders.

DNA methylation changes are a constant feature of acute myeloid leukemia. Hypomethylating drugs such as azacitidine are active in acute myeloid leukemia (AML) as monotherapy. Azacitidine monotherapy is not curative. The AML-AZA trial tested the hypothesis that DNA methyltransferase inhibitors such as azacitidine can improve chemotherapy outcome in AML. This randomized, controlled trial compared the efficacy of azacitidine applied before each cycle of intensive chemotherapy with chemotherapy alone in older patients with untreated AML. Event-free survival (EFS) was the primary end point. In total, 214 patients with a median age of 70 years were randomized to azacitidine/chemotherapy (arm-A) or chemotherapy (arm-B). More arm-A patients (39/105; 37%) than arm-B (25/109; 23%) showed adverse cytogenetics (P=0.057). Adverse events were more frequent in arm-A (15.44) versus 13.52 in arm-B, (P=0.26), but early death rates did not differ significantly (30-day mortality: 6% versus 5%, P=0.76). Median EFS was 6 months in both arms (P=0.96). Median overall survival was 15 months for patients in arm-A compared with 21 months in arm-B (P=0.35). Azacitidine added to standard chemotherapy increases toxicity in older patients with AML, but provides no additional benefit for unselected patients.

Rapid and reversible manipulations of neural activity in behaving animals are transforming our understanding of brain function. An important assumption underlying much of this work is that evoked behavioural changes reflect the function of the manipulated circuits. We show that this assumption is problematic because it disregards indirect effects on the independent functions of downstream circuits. Transient inactivations of motor cortex in rats and nucleus interface (Nif) in songbirds severely degraded task-specific movement patterns and courtship songs, respectively, which are learned skills that recover spontaneously after permanent lesions of the same areas. We resolve this discrepancy in songbirds, showing that Nif silencing acutely affects the function of HVC, a downstream song control nucleus. Paralleling song recovery, the off-target effects resolved within days of Nif lesions, a recovery consistent with homeostatic regulation of neural activity in HVC. These results have implications for interpreting transient circuit manipulations and for understanding recovery after brain lesions.

Magnetotomography, applied to fuel cells, gives rise to several questions: first, how well can the electric current density in the fuel cell be reconstructed by measuring its external magnetic field? It is quite clear that the connection between magnetic field and current alone will lead to ambiguous results. Two further relations lead to unique reconstruction: the continuity equation and Ohm's law. Second, application of Ohm's law in the membrane electrode assembly (MEA) of a fuel cell – is it not a questionable procedure? We show that in the MEA Ohm's law is not needed, when applying a rather mild approximation, we call it the ‘thin MEA approximation'. The advantage of this is the linear relation between magnetic field and electric current density, not only in the neighbourhood of the operating point but over the whole range. Third, can a functional connection be derived between resolution of the current density and the precision requirements of the measurement devices? We present a procedure leading to a unique relation between the two. This procedure can be extended to finding the optimum measuring positions, thus essentially decreasing the number of measuring points, and thus the time scale of measurable dynamical disturbances, all this without a loss of fine resolution. We present explicit numerical results for two geometries, typical for DMFC and PEMFC fuel cells.

Aromatic amino acids play an important role in ultraviolet (UV)-induced photochemical reactions in proteins. In this work, we aim at gaining insight into the photochemical reactions induced by near-UV light excitation of aromatic residues that lead to breakage of disulfide bridges in our model enzyme, Fusarium solani pisicutinase, a lipolytic enzyme. With this purpose, we acquired transient absorption data of cutinase, with supplemental experimental data on tryptophan (Trp) and lysozyme as reference molecules. We here report formation kinetics and lifetimes of transient chemical species created upon UV excitation of aromatic residues in proteins. Two proteins, lysozyme and cutinase, as well as the free amino acid Trp, were studied under acidic, neutral, and alkaline conditions. The shortest-lived species is assigned to solvated electrons (lifetimes of a few microseconds to nanoseconds), whereas the longer-lived species are assigned to aromatic neutral and ionic radicals, Trp triplet states, and radical ionic disulphide bridges. The pH-dependent lifetimes of each species are reported. Solvated electrons ejected from the side chain of free Trp residues and aromatic residues in proteins were observed 12 ns after excitation, reaching a maximum yield after ∼40 ns. It is interesting to note that the formation kinetics of solvated electrons is not pH-dependent and is similar in the different samples. On the other hand, a clear increase of the solvated electron lifetime is observed with increasing pH. This observation is correlated with H3O+being an electron scavenger. Prolonged UV illumination of cutinase leads to a larger concentration of solvated electrons and to greater absorption at 410 nm (assigned to disulphide electron adduct RSSR •−), with concomitant faster decay kinetics and near disappearance of the Trp•radical peak at 330 nm, indicating possible additional formation of TyrO•formed upon reaction of Trp•with Tyr residues. Prolonged UV illumination of cutinase also leads to a larger concentration of free thiol groups, known to originate from the dissociation of RSSR •−. Additional mechanisms that may lead to the near disappearance of Trp•are discussed. Our study provides insight into one key UV-light-induced reaction in cutinase, i.e., light-induced disruption of disulphide bridges mediated by the excitation of aromatic residues. Knowledge about the nature of the formed species and their lifetimes is important for the understanding of UV-induced reactions in humans that lead to light-induced diseases, e.g., skin cancer and cataract formation.

Detailed analysis of the effects of ultraviolet (UV) and blue light illumination of horseradish peroxidase A2, a heme-containing enzyme that reduces H2O2 to oxidize organic and inorganic compounds, is presented. The effects of increasing illumination time on the protein’s enzymatic activity, Reinheitzahl value, fluorescence emission, fluorescence lifetime distribution, fluorescence mean lifetime, and heme absorption are reported. UV illumination leads to an exponential decay of the enzyme activity followed by changes in heme group absorption. Longer UV illumination time leads to lower Tm values as well as helical content loss. Prolonged UV illumination and heme irradiation at 403nm has a pronounced effect on the fluorescence quantum yield correlated with changes in the prosthetic group pocket, leading to a pronounced decrease in the heme’s Soret absorbance band. Analysis of the picosecond-resolved fluorescence emission of horseradish peroxidase A2 with streak camera shows that UV illumination induces an exponential change in the preexponential factors distribution associated to the protein’s fluorescence lifetimes, leading to an exponential increase of the mean fluorescence lifetime. Illumination of aromatic residues and of the heme group leads to changes indicative of heme leaving the molecule and/or that photoinduced chemical changes occur in the heme moiety. Our studies bring new insight into light-induced reactions in proteins. We show how streak camera technology can be of outstanding value to follow such ultrafast processes and how streak camera data can be correlated with protein structural changes.

Mycophenolate mofetil (MMF) used in a triple-drug regimen has been shown to decrease acute rejection rates, compared to a double-drug regimen. The impact of MMF on late acute rejection (LAR) episodes has not been well described.

OBJECTIVE: The iodine intake level is important for the occurrence of thyroid disorders in a population. We have previously found that iodine in drinking water is related to iodine excretion but whether iodine is present as iodide or bound in other molecules remains unknown. DESIGN: We measured iodine in drinking water from 22 locations in Denmark. Six locations were selected by iodine content for further tap water analysis (Skagen 140 micro g/l, Samsoe 56 micro g/l, Nykoebing S. 50 micro g/l, Nakskov 40 micro g/l, Ringsted 38 micro g/l, Copenhagen 19 micro g/l). METHODS: HPLC size exclusion before (Skagen) and after (all sites) freeze drying and measurement of absorbance (280 nm) and iodine in fractions, and fluorescence spectroscopy of bulk organic matter in Skagen drinking water. RESULTS: Iodine content was unaltered after 3 Years (P=0.2). All samples contained organic molecules with characteristics similar to humic substances. Most iodine eluted with humic substances (Skagen 99%, Ringsted 98%, Nykoebing S. 90%, Copenhagen 90%, Samsoe 75%, Nakskov 40%). Changing pH and ionic strength and preincubation with iodide indicated that iodine was bound in humic substances. Humic substances may affect thyroid function but differ with geology. Geological and geochemical data agree with tap water humic substances having been released from marine deposits. Iodine is abundant in the marine environment and marine deposits are particularly rich in iodine. Correlation analysis (r=0.85, P=0.03) conform to iodine in drinking water, suggesting marine humic substances at the source rock. CONCLUSION: Iodine in Danish drinking water varied considerably. In drinking water with a high iodine content, the iodine mainly eluted with humic substances derived from marine source rock. We hypothesize that iodine in drinking water in general suggests coexisting humic substances of marine origin.

The friction coefficient of a fixed Brownian particle is calculated via an integration of the force-autocorrelation function obtained from molecular dynamics simulation. Due to finite size effects this correlation function decays exponentially to zero, which should not arise in the thermodynamic limit. An efficient way is proposed to overcome the limitation of a finite system and it is demonstrated that it is possible to reach a plateau value in the correlation function integral, which is very close to the friction coefficient determined by different methods. [Copyright &y& Elsevier]

Abstract: The scope of accreditation for testing laboratories can inhibit, in certain cases, their quick response to customers needs, if the scope is too rigid with regard to the modification of test methods and the introduction of new ones using the same measurement principles. Document EA-2-05 published by the European Cooperation for Accreditation describes possibilities to allow flexibility in accredited laboratories. Several examples of a flexible scope are given.

By analysing the surface composition of a set of protein 3D structures, complemented with predicted surface compositional information for homologous proteins, we have found significant evidence for a layer composition of protein structures. In the innermost and outermost parts of proteins there is a net negative charge, while the middle has a net positive charge. In addition, our findings indicate that the concept of conservative mutation needs substantial revision, e.g. very different spatial preferences were found for glutamic acid and aspartic acid. The alanine screening often used in protein engineering projects involves the substitution of residues to alanine, based on the assumption that alanine is a `neutral' residue. However, alanine has a high negative correlation with all but the non-polar residues. We therefore propose the use of, for example, serine as a substitute for the residues that are negatively correlated with alanine.

Based on primary amino acid sequence comparisons with other phosphoglucomutases, 12 conserved residues in the Acetobacter xylinumphosphoglucomutase (CelB) were substituted by site-directed mutagenesis, resulting in mutant enzymes with Kcatvalues [glucose-1-phosphate (G-1-P) to glucose-6-phosphate] ranging from 0 to 46% relative to that of the wild-type enzyme. In combination with a versatile set of plasmid expression vectors these proteins were used in a metabolic engineering study on sugar catabolism in Escherichia coli. Mutants of E. colideficient in phosphoglucomutase synthesize intracellular amylose when grown on galactose, due to accumulation of G-1-P. Wild-type celBcan complement this lesion, and we show here that the ability of the mutant enzymes to complement is sensitive to variations in their respective in vitrodetermined Kcatand KmG-1-Pvalues. Reduced catalytic efficiencies could be compensated by increasing the CelB expression level, and in this way a mutant protein (substitution of Thr-45 to Ala) displaying a 7600-fold reduced catalytic efficiency could be used to eliminate the amylose accumulation. Complementation experiments with the homologous phosphoglucomutase indicated that a KmG-1-Pvalue significantly below that of CelB is not critical for the in vivoconversion of the substrate.

Epidemiological studies in China provide reason to suspect that a rich garlic content in the diet might reduce the proliferation of tumors in humans. We conducted experiments on human tumor cell lines and determined the influence of a garlic powder preparation, a garlic extract (reported as 8–10% L(+)-alliin enriched), and a combination thereof, on cellular proliferation in cell cultures, employing the widely used indirect neutral red procedure. Garlic powder failed to inhibit the growth of human hepatoma HepG2 or human colorectal carcinoma Caco2 cells at concentrations of up to 1000 μg/ml. Garlic extract, in which the alliin content was highly enriched was also unable to inhibit the growth of these cells. However, when the garlic extract was supplemented with garlic powder (to 10% final concentration) there was a concentration-dependent clear inhibition of tumor cell growth (IC50values of 330 μg/ml for HepG2 and 480 μg/ml for Caco-2 cells). The growth of the human lymphatic leukemia cell line CCRF CEM was significantly inhibited in a dose-dependent manner by both garlic powder and garlic extract at concentrations as low as 30 μg/ml. However, no potentiation of this effect occured upon mixing of the two preparations. Our results suggest that the antiproliferative effects of garlic may be due to breakdown products of alliin, such as allicin or polysulfides, rather than alliin itself, since the addition of an alliinase system (garlic powder) to an alliin enriched preparation without alliinase (garlic extract) potentiated the effects observed with the two preparations alone.

Here we present an investigation of the contacts that cysteines make with residues in their three-dimensional environment and a comprehensive analysis of the conformational features of 351 disulphide bridges in 131 non-homologous single-chain protein structures. Upstream half-cystines preferentially have downstream neighbours, whereas downstream half-cystines have mainly upstream neighbours. Non-disulphide bridged cysteines (free cysteines) have no preference for upstream or downstream neighbours. Free cysteines have more contacts to non-polar residues and fewer contacts to polar/charged residues than half-cystines, which correlates with our observation that free cysteines are more buried than half-cystines. Free cysteines prefer to be located in α-helices while no clear preference is observed for half-cystines. Histidine and methionine are preferentially seen nearby free cysteines. Tryptophan is found preferentially nearby half-cystines. We have merged sequential and spatial information, and highly interesting novel patterns have been discovered. The number of cysteines per protein is typically an even number, peaking at four. The number of residues separating two half-cystines is preferentially 11 and 16. Left-handed and right-handed disulphide bridges display different conformational parameters. Here we present side chain torsion angle information based on a 5–12 times larger number of disulphide bridges than has previously been published. Considering the importance of cysteines for maintaining the 3D-structural scaffold of proteins, it is essential to have as accurate information as possible concerning the packing and conformational preferences. The present work may provide key information for engineering the protein environment around cysteines.

The reaction of ReCl5with a porphyrin H2(P) [2, 3] in refluxing trichlorobenzene represents a very efficient synthesis of oxorhenium(V) porphyrins ReO(P)X where X is a uninegative anion. Thus, rhenium is inserted to octaethylporphyrin and a variety of tetraarylporphyrins. The primary products are the paramagnetic trichlororhenium(V) porphyrins, ReCl3(P), which are remarkably resistant to hydrolysis. If moisture is not rigorously excluded from the metal insertion system, chlorooxorhenium(V) porphyrins ReO(P)Cl are formed which during alumina chromatography are converted to the methoxides ReO(P)OMe. All complexes ReO(P)X and ReCl3(P) are subject to alkaline hydrolysis yielding the μ-oxo complexes [ReO(P)]2O which are convenient starting materials for a variety of mononuclear species ReO(P)X [X = OMe, OEt, OiPr, OtBu, F, Cl, Br, OCIO3, OAc, OBz, OCN, NCS] on acidolysis with a number of monobasic inorganic and organic acids HX or reaction with alkali salts MX in presence of acetic acid. In the case of tetramesitylporphyrin, hydrolysis yields a mononuclear hydroxooxorhenium(V) porphyrin. The species ReCl3(P) and ReO(P)X are characterized by UV/VIS, IR, 1H NMR and mass spectra.

The kinetics of shaping of periodic surface profiles under the action of surface selfdiffusion were calculated for the special case of anisotropic surface energy. The orientation-dependent surface energy was allowed to contain a local minimum of very high curvature (cusp). The orientation of this cusp was equal to the macroscopic orientation of the crystal surface. The periodic surface profiles exhibited in all cases extended, nearly flat regions centered at the cusp orientation. This type of faceting which causes the profile to be trapezoidal in shape agrees well with experimentally observed profiles on (111) and (100) Ni single crystal surfaces. A procedure is outlined by which the orientation-dependent surface energy along a certain azimuth and the surface self-diffusion coefficient can be extracted from the decay kinetics of faceted periodic surface profiles. This procedure demands the accurate experimental assessment of profile shapes and amplitudes.

Solution pH is a determinant parameter on protein function and stability, and its inclusion in molecular dynamics simulations is attractive for studies at the molecular level. Current molecular dynamics simulations can consider pH only in a very limited way, through a somewhat arbitrary choice of a set of fixed charges on the titrable sites. Conversely, continuum electrostatic methods that explicitly treat pH effects assume a single protein conformation whose choice is not clearly defined. In this paper we describe a general method that combines both titration and conformational freedom. The method is based on a potential of mean force for implicit titration and combines both usual molecular dynamics and pH-dependent calculations based on continuum methods. A simple implementation of the method, using a mean field approximation, is presented and applied to the bovine pancreatic trypsin inhibitor. We believe that this constant-pH molecular dynamics method, by correctly sampling both charges and conformation, can become a valuable help in the understanding of the dependence of protein function and stability on pH. © 1997 Wiley-Liss Inc.

The X-ray scattering intensity from highly viscous, liquid glycerol has been measured using MoKα-radiation (0.2 < qÅ < 10) between 250 K and 350 K. The corrected spectra were Fourier transformed to obtain the atomic radial distribution function.

This is a case study for the treatment of the partial differential equations (PDEs) of cell modelling. This part deals with the calculation of the primary and secondary current distribution in a cell using finite difference (FD) methods for the discretization. For nonuniform resistivity and shaped boundaries, conservative FD methods are discussed.

A mean threedimensional density distribution is determined by comparing the surroundings of all atoms of a melt. Contrary to the definition of the pair distribution function, the surroundings of the different atoms are allowed to rotate against each other before being added up.

Abstract.: The trypsin family of serine proteases is one of the most studied protein families, with a wealth of amino acid sequence information available in public databases. Since trypsin-like enzymes are widely distributed in living organisms in nature, likely evolutionary scenarios have been proposed. A novel methodology for Fourier transformation of biological sequences (FOTOBIS) is presented. The methodology is well suited for the identification of the size and extent of short repeats in protein sequences. In the present paper the trypsin family of enzymes is analyzed with FOTOBIS and strong evidence for tandem gene duplication is found. A likely evolutionary path for the development of present-day trypsins involved an intrinsic extensive tandem gene duplication of a small DNA fragment of 15–18 nucleotides, corresponding to five or six amino acids. This ancestral trypsin gene was subsequently duplicated, leading to the earliest version of a full-sized trypsin, from which the contemporary trypsins have developed.

Characteristic formulae have been introduced by Graf and Sifakis to relate equational reasoning about proceses to reasoning in a modal logic, and therefore to allow proofs about processes to be carried out in a logical framework. This work, which concerned finite processes and bisimulation-like equivalences, has later on been extended to finite state processes and further equivalences. Based upon an intuitionistic understanding of Hennessy-Milner Logic (HML) with mutual recursion, we extend these results to cover bisimulation-like preorders, which are sensitive to liveness properties. This demonstrates the expressive power of intuitionistically interpreted HML with mutual recursion, and it builds the theoretical basis for a uniform and efficient method to automatically verify bisimulation-like relations between processes by means of model checking.Copyright 1994, 1999 Academic Press, Inc.

We introduce three models of probabilistic processes, namely, reactive, generative, and stratified. These models are investigated within the context of PCCS, an extension of Milner's SCCS in which each summand of a process summation expression is guarded by a probability and the sum of these probabilities is 1. For each model, we present a structural operational semantics of PCCS and a notion of bisimulation equivalence which we prove to be a congruence. We also show that the models form a hierarchy: the reactive model is derivable from the generative model by abstraction from the relative probabilities of different actions, and the generative model is derivable from the stratified model by abstraction from the purely probabilistic branching structure. Moreover, the classical nonprobabilistic model is derivable from each of these models by abstraction from all probabilities.Copyright 1995, 1999 Academic Press. Inc.

Neural networks provide a basis for semiempirical studies of pattern matching between the primary and secondary structures of proteins. Networks of the perceptron class have been trained to classify the amino-acid residues into two categories for each of three types of secondary feature: α-helix or not, β-sheet or not, and random coil or not. The explicit prediction for the helices in rhodopsin is compared with both electron microscopy results and those of the Chou-Fasman method. A new measure of homology between proteins is provided by the network approach, which thereby leads to quantification of the differences between the primary structures of proteins.

We have performed model calculations for the deposition of metal ions in the vicinity of the tip of a scanning tunneling microscope. Our results show that near the tip mass transport towards the substrate is greatly reduced. These findings may explain shielding effects that have been observed experimentally.

A computer method for folding protein backbones from distance inequalities is presented. It involves an algorithm that uses a novel approach for handling inequalities through the minimization of a continuous energy function. Tests of the folding algorithm have been carried out on a small protein, the 6PTI (bovine pancreatic trypsin inhibitor) with 56 amino acid residues, and on a medium-size protein, the 1TRM (rat trypsin) with 223 amino acid residues. Reconstructions based on a real-valued distance matrix led to folded three-dimensional structures with root-mean-square values of 0·04 Å when compared with the crystallographic data. The obtained root-mean-square measures were of the order of 1 Å, when distance inequalities were used for the reconstruction. Subsequently, the folding approach has been applied to distance inequalities predicted by neural network techniques that use the amino acid sequence as the only input. The inaccuracy in the inequalities predicted by the neural network was the reason for the root-mean-square value of 5·2 Å. An error analysis of the method for reconstruction was performed and showed that no more than 3% inaccurate distance inequalities could be corrected for. Finally, a simple technique for root-mean-square comparisons of different protein structures is discussed. Copyright 1993, 1999 Academic Press

In the present investigation a method is described for culturing cerebellar granule cells (glutamatergic neurons), cerebral cortical neurons (GABAergic neurons) and cortical astrocytes on Cytodex 3 microcarriers. It was possible to obtain a high yield of attached neurons and astrocytes on the microcarriers and the cell specific characteristics such as the ability to release neurotransmitter (neurons) and a high activity of glutamine synthetase (astrocytes) were preserved. This system, allowing mixtures of neurons and astrocytes at any given ratio to be produced, may constitute an attractive model system by which the interaction between neurons and astrocytes with regard to exchange of neurotransmitter precursors as well as other compounds may be studied.

Abstract:  In response to the requirements of the "Global Approach" in Germany, a national accreditation system has been established based on traditional experiences in the recognition of the competence of laboratories and certification bodies. In 1991, the German Accreditation Council (DAR) was founded as a coordinating body supported by the Federal and State Ministries and German industry. In this way, it was possible to organise coordinated representation in international bodies, to offer a forum for cooperation between authorities and industry, and to provide for a structure subdivided into sectors which better fits the needs of the industrial sectors and gives them the necessary transparency and acceptance. The DAR itself does not carry out accreditations. This is done by the accreditation bodies represented in the DAR and specialised in for specific subjects, thereby having a close connection with expert groups of a high technical competence in their specific technical fields. At the end of this paper, the procedure for the assessment of the technical competence of a laboratory, an important part of the accreditation, is described.

The kinetics of shaping of periodic surface profiles under the action of surface selfdiffusion were calculated for the special case of anisotropic surface energy. The orientation-dependent surface energy was allowed to contain a local minimum of very high curvature (cusp). The orientation of this cusp was equal to the macroscopic orientation of the crystal surface. The periodic surface profiles exhibited in all cases extended, nearly flat regions centered at the cusp orientation. This type of faceting which causes the profile to be trapezoidal in shape agrees well with experimentally observed profiles on (111) and (100) Ni single crystal surfaces. A procedure is outlined by which the orientation-dependent surface energy along a certain azimuth and the surface self-diffusion coefficient can be extracted from the decay kinetics of faceted periodic surface profiles. This procedure demands the accurate experimental assessment of profile shapes and amplitudes. [ABSTRACT FROM AUTHOR]

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

If the results from various proficiency tests are used to compare the performance of accredited and non-accredited laboratories, great care must be taken not to come to contradicting conclusions when interpreting them. This paper intends to draw the attention to various aspects that should be taken into account when trying to make conclusions from the relative performance of accredited laboratories in proficiency testing.

Development of differential cell culture systems has facilitated the study of cellular and physiological actions of growth factors. Here we report the novel effects of insulin and insulin-like growth factor (IGF)-I on energy metabolism in cerebral cortical neurones, astrocytes and co-cultures thereof. Incorporation of label from 1-13Cglucose into lactate has been shown to involve both glycolysis and the tricarboxylic acid cycle in astrocytes. Thus 13C nuclear magnetic resonance spectroscopy was used to monitor mitochondrial function by measuring 13C labelling of the C-2 position of lactate. It could be demonstrated that insulin and IGF-I have similar effects on mitochondria but individual effects on cytosolic glucose metabolism. Evidence is presented that IGF-I and insulin stimulate neurones to release factors affecting astrocytic lactate production. Furthermore, lactate released from neuronal–astrocytic co-cultures was mostly of astrocytic origin, implicating the importance of lactate for neuronal metabolism.

Recent results concerning the structure of microparacrystals established in different melts are reported. In spite of structural differences among the investigated samples the reduced density is always the same. This approach is possibly a first step towards a correlation between the hard sphere concept of statistical mechanics and our refined structural analysis.