Identification and mass spectrometric sequence studies of fragments of l-asparaginase produced during freeze/thaw cycling

L-Asparaginase isolated from Er. chrysanthemi was found to lose activity upon exposure to consecutive freeze/thaw cycles. The cause(s) for this loss of activity were investigated using multiple techniques. SEC using UV, RI and light scattering detectors and SDS-PAGE indicated that the l-asparaginase molecule fragments upon exposure to repeated freezing and thawing cycles. Following up on this information, mass spectrometry was used to identify the fragments as small peptides of molecular weight 615 Da, 1424 Da and 1665 Da. Automated Edman sequencing of the frozen and thawed mixture confirmed the presence of fragments and contributed some sequence information. Mass spectral data and sequence studies of these fragments in conjunction with the known sequence of the molecule placed all the fragments within the last 28 C-terminal amino acids. A study of this region using the published 3 dimensional x-ray crystallographic structure of l-asparaginase revealed that the C-terminal region is exposed and can interact with water. The IBI MacVector program "Protein Tool Box" predicted that this region is hydrophilic, has a high surface probability and a strong tendency to interact with water. Both tendencies suggest a potential for bond stress during freeze/thaw cycling. This region is not involved at the catalytic core of the enzyme, but fragmentation in this area may result in unfolding and denaturation of the monomer followed by subsequent aggregation into large, insoluble entities and the loss of enzymatic activity.     

P systems with active membranes: trading time for space

We consider recognizer P systems having three polarizations associated to the membranes, and we show that they are able to solve the PSPACE-complete problem Quantified 3SAT when working in polynomial space and exponential time. The solution is uniform (all the instances of a fixed size are solved by the same P system) and uses only communication rules: evolution rules, as well as membrane division and dissolution rules, are not used. Our result shows that, as it happens with Turing machines, this model of P systems can solve in exponential time and polynomial space problems that cannot be solved in polynomial time, unless P = SPACE.     

A study on learning robustness using asynchronous 1D cellular automata rules

Numerous studies can be found in literature concerning the idea of learning cellular automata (CA) rules that perform a given task by means of machine learning methods. Among these methods, genetic algorithms (GAs) have often been used with excellent results. Nevertheless, few attention has been dedicated so far to the generality and robustness of the learned rules. In this paper, we show that when GAs are used to evolve asynchronous one-dimensional CA rules, they are able to find more general and robust solutions compared to the more usual case of evolving synchronous CA rules.     

Amaranth protein films from thermally treated proteins

The usefulness of amaranth protein isolates, native and thermally treated, in edible films preparation was studied. Protein films were prepared by casting using glycerol as plasticizer. Films from amaranth native protein isolates showed low water vapor permeability (WVP) but poor mechanical properties. In order to improve this functionality, proteins were treated at 70 and 90 °C which corresponds to the denaturation temperature of the protein fractions present in the isolates. The unfolded conformation of these thermally treated proteins, when partially or totally denatured, favors the interactions between polypeptide chains during the film formation. These interactions lead to a greater cross-linking degree, which was reflected in the lower amount of water-soluble free peptides that were linked to the matrix. In these thermally treated protein films, a greatest contribution of disulfide and hydrogen bonds to the films stabilization was observed. These changes in the films structural properties would confer them a greater tensile strength and lower water solubility but higher thickness and WVP.     

alpha-Melanocyte-stimulating hormone during human perinatal life

To obtain information on human pituitary intermediate lobe activity throughout the perinatal period, plasma alpha MSH immunoreactivity (IR) was measured in 106 newborns at delivery and during the first week of postnatal life. Subjects were divided into groups according to gestational age at birth, mode of parturition, and antenatal state of health. Plasma alpha MSH IR decreased progressively from severe preterm to fullterm neonates born by vaginal delivery (VD; P < 0.001) or cesarean section (CS) with and without prenatal distress (P < or = 0.001 in both cases). alpha MSH IR was due, in all studied conditions, to three major forms: desacetyl alpha MSH, alpha MSH, and diacetyl alpha MSH. Desacetyl alpha MSH was always the most represented form, but it decreased from 75-80% of the total in severe premature to 40-45% in mature infants. In term neonates, total alpha MSH IR values were higher in subjects born by normal VD than by elective CS (P < or = 0.05), in complicated than in normal VD (P < or = 0.01), and in CS performed because of fetal distress than in elective CS (P < or = 0.01). No significant difference was detectable in mature subjects in the percentages of the three alpha MSH forms in relation to the mode of delivery and fetal state during antenatal life or at parturition. Twelve hours after birth, total alpha MSH IR significantly decreased in all groups of term newborns, reaching a plateau of 0.8-1.4 pmol/L. In premature infants, similar concentrations were detectable by the fourth postnatal day. We conclude that 1) alpha MSH IR intermediate lobe secretion progressively decreases throughout the third trimester of pregnancy; 2) stress, including that pertinent to parturition, stimulates alpha MSH IR release; and 3) pituitary intermediate lobe activity declines shortly after birth independently of the maturity reached by the fetus, the mode of parturition, and the presence of antenatal chronic distress, although the process is slightly retarded in premature newborns.     

Fasting insulin and apolipoprotein B levels and low-density lipoprotein particle size as risk factors for ischemic heart disease

CONTEXT: Epidemiological studies have established a relationship between cholesterol and low-density lipoprotein cholesterol (LDL-C) concentrations and the risk of ischemic heart disease (IHD), but up to half of patients with IHD may have cholesterol levels in the normal range. OBJECTIVE: To assess the ability to predict the risk of IHD using a cluster of nontraditional metabolic risk factors that includes elevated fasting insulin and apolipoprotein B levels as well as small, dense LDL particles. DESIGN: Nested case-control study. SETTING: Cases and controls were identified from the population-based cohort of the Quebec Cardiovascular Study, a prospective study conducted in men free of IHD in 1985 and followed up for 5 years. PARTICIPANTS: Incident IHD cases were matched with controls selected from among the sample of men who remained IHD free during follow-up. Matching variables were age, smoking habits, body mass index, and alcohol consumption. The sample included 85 complete pairs of nondiabetic IHD cases and controls. MAIN OUTCOME MEASURES: Ability of fasting insulin level, apolipoprotein B level, and LDL particle diameter to predict IHD events, defined as angina, coronary insufficiency, nonfatal myocardial infarction, and coronary death. RESULTS: The risk of IHD was significantly increased in men who had elevated fasting plasma insulin and apolipoprotein B levels and small, dense LDL particles, compared with men who had normal levels for 2 of these 3 risk factors (odds ratio [OR], 5.9; 95% confidence interval [CI], 2.3-15.4). Multivariate adjustment for LDL-C, triglycerides, and high-density lipoprotein cholesterol (HDL-C) did not attenuate the relationship between the cluster of nontraditional risk factors and IHD (OR, 5.2; 95% CI, 1.7-15.7). On the other hand, the risk of IHD in men having a combination of elevated LDL-C and triglyceride levels and reduced HDL-C levels was no longer significant (OR, 1.4; 95% CI, 0.5-3.5) after multivariate adjustment for fasting plasma insulin level, apolipoprotein B level, and LDL particle size. CONCLUSION: Results from this prospective study suggest that the measurement of fasting plasma insulin level, apolipoprotein B level, and LDL particle size may provide further information on the risk of IHD compared with the information provided by conventional lipid variables.     

Hereditary multi-infarct dementia. Morphological and clinical studies of a new disease

The purified isopropylmalate synthase of Alcaligenes eutrophus H 16 reacted with the following alpha-keto acids and acyl-coenzyme A derivatives (in the sequence of decreasing affinities): alpha-ketoisovalerate, alpha-keto-n-valerate, alpha-ketobutyrate and pyruvate; acetyl-CoA, propionyl-CoA, butyryl-CoA, malonyl-CoA, valeryl-CoA, and crotonyl0CoA. alpha-Ketoisocaproate, however, is a strong inhibitor of the enzyme. All reactions catalyzed by isopropylmalate synthase were inhibited to the same extent by the endproduct L-leucine. The substrate saturation curves of alpha-ketoisovalerate or other alpha-keto acids and of acetyl-coenzyme A or other acyl-CoA derivatives had intermediary plateau regions; the Hill coefficient alternated between nH-values higher and lower than 1.0, indicating changes from positive to negative and from negative to positive cooperativity for the substrates. The products, isopropylmalate and free coenzyme A, showed competitive inhibition patterns against both substrates (alpha-ketoisovalerate and acetyl-CoA). Free coenzyme A (1 micronM) inactivated the enzyme irreversibly. The 3'-phosphate of coenzyme A and the free carboxyl group of alpha-ketoisovalerate were involved in optimal binding of these substrates, but 3'-dephospho-acetyl-coenzyme A and the methylester of alpha-keto-isovalerate were also converted by this enzyme. A CH3--CH2-grouping of the alpha-keto acids seemed to be necessary for binding this substrate.     

Self interference by rain scattering in satellite radio links

Scattering by rain at millimetre wavelengths may cause disturbance on the same link which uses the incident wave as an information carrier. A numerical evaluation of this disturbance is performed and its dependence on frequency, rain rate, rain depth and antenna gain is presented.     

Comprehensive numerical simulation of threshold-voltage transients in nitride memories

A new non-local algorithm for accurately calculating the band-to-band tunneling current suitable for TCAD semiconductor simulators is proposed in this paper. The proposed algorithm captures the essential physics of multi-dimensional tunneling in a 2D structure, and is designed to be robust and to achieve independence on the mesh grid. The new algorithm enables accurate modeling of T-FET and investigation of its device physics.     

Generation-dependent molecular recognition controls self-assembly in supramolecular dendron-virus complexes

In this work molecular dynamics simulation identifies a clear link between the dendron-virus multivalent molecular recognition and the nature of the consequent self-assembly. Data demonstrate how a weak hydrophobic association is transformed in an electrostatic self-assembly, orders of magnitude stronger, depending on the dendron generation used to assemble the viruses. This opens a new frontier in the engineering of hierarchical self-assemblies, potentially enabling the control of the supramolecular properties by acting at the single-molecule level.