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PubMed1984

Long term stability of rat sleep quantified by microcomputer analysis.

An inexpensive microcomputer system is described for the direct recording of electrographic data from animals. Using this system, electrographic data can be recorded continuously on a polygraph and simultaneously quantitated by the computer, for days or weeks. Our system quantifies the amounts of delta waves, spindle bursts, hippocampal RSA activity and movement spikes for 15 sec epochs. These electrographic data are stored by the computer and subsequently can be used to score sleep stages. We find that the computer reliably counts waves; using these data, it can then score sleep stages off-line with about 90% accuracy. With this system, we find that the minutes/hour of both SWS and REM are remarkably stable from day to day. The absolute number of delta waves, spindle bursts, trains of RSA and movement counts/hour also remain stable from day to day. This type of system should find significant application in situations where quantitation of longterm effects of drugs, diets and other environmental inputs on sleep states or EEG wave bands are of interest.

Animals↗
PubMed1987

Sense and antisense transcription of bacteriophage T4 gene 32. Processing and stability of the mRNAs.

Analysis of bacteriophage T4 gene 32 transcription has revealed a multiplicity of mRNAs. In plasmids, gene 32 is expressed primarily from a strong promoter that is shut off after phage infection. In a wild-type infection, gene 32 is initially transcribed from prereplicative polycistronic and monocistronic promoters; subsequently, a monocistronic late mRNA predominates. This transcript, as well as a post-transcriptionally processed product of the earlier mRNA, can be stable. The eventual degradation of the stable mRNAs is temporally regulated by the phage. Finally, the transcription termination region of gene 32 can function as an antisense promoter both in vitro and in vivo.

Base Sequence↗
PubMed1994

Conformational transitions of duplex and triplex nucleic acid helices: thermodynamic analysis of effects of salt concentration on stability using preferential interaction coefficients.

For order-disorder transitions of double- and triple-stranded nucleic acid helices, the midpoint temperatures Tm depend strongly on a +/-, the mean ionic activity of uniunivalent salt. Experimental determinations of dTm/d ln a +/- and of the enthalpy change (delta H(o)) accompanying the transition in excess salt permit evaluation of delta gamma, the stoichiometrically weighted combination of preferential interaction coefficients, each of which reflects thermodynamic effects of interactions of salt ions with a reactant or product of the conformational transition (formula; see text) Here delta H(o) is defined per mole of nucleotide by analogy to delta gamma. Application of Eq. 1 to experimental values of delta H(o) and Tm yields values of delta gamma for the denaturation of B-DNA over the range of NaCl concentrations 0.01-0.20 M (Privalov et al. (1969), Biopolymers 8,559) and for each of four order-disorder transitions of poly rA.(poly rU)n, n = 1, 2 over the range of NaCl concentrations 0.01-1.0 M (Krakauer and Sturtevant (1968), Biopolymers 6, 491). For denaturation of duplexes and triplexes, delta gamma is negative and not significantly dependent on a +/-, but delta gamma is positive and dependent on a +/- for the disproportionation transition of poly rA.poly rU duplexes. Quantitative interpretations of these trends and magnitudes of delta gamma in terms of coulombic and excluded volume effects are obtained by fitting separately each of the two sets of thermodynamic data using Eq. 1 with delta gamma PB evaluated from the cylindrically symmetric Poisson-Boltzmann (PB) equation for a standard model of salt-polyelectrolyte solutions. The only structural parameters required by this model are: b, the mean axial distance between the projections of adjacent polyion charges onto the cylindrical axis; and a, the mean distance of closest approach between a salt ion center and the cylindrical axis. Fixing bMS and aMS for the multi-stranded (ordered) conformations, we determined the corresponding best fitted values of bSS and aSS for single-stranded RNA and DNA. The resulting best fitted values of aSS are systematically less than aDS by 2-4 A. Uncertainty in the best-fitted values of bSS is significantly lower than in the aSS, because bMS is known with relatively high precision and because the larger uncertainty in aMS has a relatively small effect on the best-fitted values of bSS:bSS = 3.2 +/- 0.6 A for single-stranded poly rA and poly rU; and bSS = 3.4 +/- 0.2 A for single-stranded DNA. These values are approximately one-halt of those expected for a fully extended single-stranded conformation. With the best fitted values of ass and bss, our calculations of delta gamma PB are in close quantitative agreement with experimental observations on each of five nucleic acid order-disorder transitions.

DNA↗
PubMed2003

Theoretical analysis of the electronic structure and bonding stability of the TCNE dimer dianion (TCNE) 2 2-.

The (TCNE)(2)(2)(-) dimer dianion formed by connecting two TCNE(-) anions via a four-center, two-electron pi-orbital bond is studied using ab initio theoretical methods and a model designed to simulate the stabilization due to surrounding counterions. (TCNE)(2)(2)(-) is examined as an isolated species and in a solvation environment representative of tetrahydrofuran (THF) solvent. The intrinsic strength of this novel bond and the influences of internal Coulomb repulsions, of solvent stabilization and screening, and of counterion stabilization are all considered. The geometry, electronic and thermodynamic stabilities, electronic absorption spectra, and electron detachment energies of this novel dianion are examined to help understand recent experimental findings. Our findings lead us to conclude that the (TCNE)(2)(2)(-) dianion's observation in solid materials is likely a result of its stabilization by surrounding countercations. Moreover, our results suggest the dianion is geometrically metastable in THF solution, with a barrier to dissociation into two TCNE(-) anions that can be quickly surmounted at room temperature but not at 77 K. This finding is consistent with what is observed in laboratory studies of low- and room-temperature solutions of salts containing this dianion. Finally, we assign two peaks observed (at 77 K in methyl-THF glass) in the UV-vis region to (1) electronic transitions involving the four-center orbitals and (2) detachment of an electron from the four-center pi-bonding orbital to generate (TCNE)(2)(-) + e(-).

Journal Article↗
PubMed2005

Fixation stability following high tibial osteotomy: a radiostereometric analysis.

Fifteen patients with varus gonarthrosis underwent high tibial osteotomy and internal fixation with an L-shaped rigid plate. In 9 patients, an average wedge size of 7.1 degrees was resected leaving the medial cortex of the proximal tibia intact (group 1). In 6 patients, the medial cortex of the proximal tibia was unintentionally fractured during surgery when an average 10.7 degrees wedge was resected (group 2). Postoperatively, patients were monitored with serial radiostereometric analysis (RSA), conventional radiographs, and clinical evaluation for 1 year. In group 2, RSA revealed a 1.3-mm increase in lateral displacement of the distal tibial segment within 3 weeks following surgery. Twelve weeks after surgery, micromotion between tibial segments was below the precision of the RSA setup in 14 of 15 patients. These findings indicate that in cases with larger wedge sizes (>8 degrees), fracture of the medial cortex of the proximal tibia was frequent and resulted in significant lateral displacement of the distal tibia relative to the tibial plateau. In such cases, prophylactic additional medial fixation rather than lateral L-plate fixation alone is advised to minimize the propensity for lateral displacement of the distal tibia and to avoid subsequent loss of correction.

Bone Malalignment↗
PubMed1995

FK506 binding protein mutational analysis. Defining the surface residue contributions to stability of the calcineurin co-complex.

The 12- and 13-kDa FK506 binding proteins (FKBP12 and FKBP13) are cis-trans peptidyl-prolyl isomerases that bind the macrolides FK506 (Tacrolimus) and rapamycin (Sirolimus). The FKBP12.FK506 complex is immunosuppressive, acting as an inhibitor of the protein phosphatase calcineurin. We have examined the role of the key surface residues of FKBP12 and FKBP13 in calcineurin interactions by generating substitutions at these residues by site-directed mutagenesis. All mutants are active catalysts of the prolyl isomerase reaction, and bind FK506 or rapamycin with high affinity. Mutations at FKBP12 residues Asp-37, Arg-42, His-87, and Ile-90 decrease calcineurin affinity of the mutant FKBP12.FK506 complex by as much as 2600-fold in the case of I90K. Replacement of three FKBP13 surface residues (Gln-50, Ala-95, and Lys-98) with the corresponding homologous FKBP12 residues (Arg-42, His-87, and Ile-90) generates an FKBP13 variant that is equivalent to FKBP12 in its affinity for FK506, rapamycin, and calcineurin. These results confirm the role of two loop regions of FKBP12 (residues 40-44 and 84-91) as part of the effector face that interacts with calcineurin.

Amino Acid Sequence↗
PubMed2005

Modulation of Streptomyces leucine aminopeptidase by calcium: identification and functional analysis of key residues in activation and stabilization by calcium.

Streptomyces griseus leucine aminopeptidase (SGAP), which has two zinc atoms in its active site, is clinically important as a model for understanding the structure and mechanism of action of other metallopeptidases. SGAP is a calcium-activated and calcium-stabilized enzyme, and its activation by calcium correlates with substrate specificity. In our previous study, we found a non-calcium-modulated leucine aminopeptidase secreted by Streptomyces septatus, the primary structure of which showed 71% identity with SGAP. In this study, we constructed chimeras of SGAP and S. septatus aminopeptidase by using an in vivo DNA shuffling system and several mutant enzymes by site-directed mutagenesis to identify the key residues in this modulation by calcium. We identified the key residues Asp-173 and Asp-174 of SGAP associated with both SGAP activation and stabilization by calcium. We also showed that the known calcium-binding site, which is composed of Asp-3, Ile-4, Asp-262, and Asp-266 of SGAP, only contributes to SGAP stabilization by calcium. Furthermore, we identified an important residue, Glu-196, that functions in cooperation with Asp-173, Asp-174, and calcium to increase the catalytic activity of SGAP.

Amino Acid Sequence↗
PubMedDate not supplied

Analysis of dimethyl hydrogen phosphite and its stability under simulated physiological conditions.

In a study by the National Toxicology Program, dimethyl hydrogen phosphite (DMHP) was shown to cause dose-related neoplastic lesions in the lungs and forestomachs of Fischer 344 rats. This investigation was carried out to study the stability of this carcinogen under conditions similar to those that the chemical may encounter in the physiological environment. To carry out these studies, capillary gas chromatography was utilized to analyze DMHP. The method was linear over a range of 10 to at least 1000 ng. High-performance liquid chromatography (HPLC) also was used to analyze DMHP and its degradation products. In aqueous solutions, DMHP was stable for a period of time before degradation began. Once the process began, degradation continued until 10-20% of the original concentration was reached and further decomposition was minimal. At 10% concentration in 0.1M phosphate buffer, pH 7.4, DMHP was stable for 3.6 h at 37 degrees C. This stability period increased at lower temperature, at lower DMHP concentration, and in slightly more alkaline buffer (pH 8). After the stability period, DMHP disappeared from the solution and this disappearance followed a first order kinetics with a rate dependent upon temperature, concentration of DHMP, and the pH of the solution. The half-time of disappearance of DMHP under the conditions mentioned above was 2.4 h, which increased at lower temperature, at lower DMHP concentration, and in slightly more alkaline buffer (pH 8). The decomposition products of DMHP were identified by HPLC and proton nuclear magnetic resonance (1H-NMR) spectroscopy as methanol, monomethyl hydrogen phosphite, and orthophosphorous acid.

Chemical Phenomena↗
PubMed1993

Thermodynamic and kinetic stabilities of hen-egg lysozyme and its chemically modified derivatives: analysis of the transition state of the protein unfolding.

For the stabilization of a protein against irreversible denaturation caused by rapid reaction of the unfolded form of the protein (kinetic stabilization), the free energy change of activation for unfolding should be increased. First, we demonstrated that this strategy was effective to stabilize a protein against protease digestion. For kinetic stabilization, it is important to stabilize a protein at a site where the local structures are largely unfolded in the transition state for unfolding. We developed a method to find such sites by comparison of the thermodynamic stabilities and the unfolding rate constants between unmodified and modified proteins. Application of this method to analyze the transition state of hen-egg lysozyme using some chemically modified derivatives is also described. Moreover, it was confirmed that the protease digestion method is superior to the relaxation method for estimation of the unfolding rate constant. Namely, the protease digestion method may be useful in analyzing the transition state of protein unfolding.

Animals↗
PubMed1999

A mechanistic analysis of the increase in the thermal stability of proteins in aqueous carboxylic acid salt solutions.

The stability of proteins is known to be affected significantly in the presence of high concentration of salts and is highly pH dependent. Extensive studies have been carried out on the stability of proteins in the presence of simple electrolytes and evaluated in terms of preferential interactions and increase in the surface tension of the medium. We have carried out an in-depth study of the effects of a series of carboxylic acid salts: ethylene diamine tetra acetate, butane tetra carboxylate, propane tricarballylate, citrate, succinate, tartarate, malonate, and gluconate on the thermal stability of five different proteins that vary in their physico-chemical properties: RNase A, cytochrome c, trypsin inhibitor, myoglobin, and lysozyme. Surface tension measurements of aqueous solutions of the salts indicate an increase in the surface tension of the medium that is very strongly correlated with the increase in the thermal stability of proteins. There is also a linear correlation of the increase in thermal stability with the number of carboxylic groups in the salt. Thermal stability has been found to increase by as much as 22 C at 1 M concentration of salt. Such a high thermal stability at identical concentrations has not been reported before. The differences in the heat capacities of denaturation, deltaCp for RNase A, deduced from the transition curves obtained in the presence of varying concentrations of GdmCl and that of carboxylic acid salts as a function of pH, indicate that the nature of the solvent medium and its interactions with the two end states of the protein control the thermodynamics of protein denaturation. Among the physico-chemical properties of proteins, there seems to be an interplay of the hydrophobic and electrostatic interactions that lead to an overall stabilizing effect. Increase in surface free energy of the solvent medium upon addition of the carboxylic acid salts appears to be the dominant factor in governing the thermal stability of proteins.

Carboxylic Acids↗
PubMed2005

Comparative analysis of the effects of four mood stabilizers in SH-SY5Y cells and in primary neurons.

OBJECTIVES: The mood-stabilizing drug valproic acid (VPA) exerts a neurotrophic effect on the human neuroblastoma cell line, SH-SY5Y. We aimed to establish whether other mood-stabilizing drugs have a similar action and which signalling pathways mediate this process. METHODS: We analysed the effects of the mood stabilizers VPA, lithium, carbamazepine and lamotrigine on proliferation, survival, neurite outgrowth and extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) activation using the SH-SY5Y cell line. We also compared their effects in primary neurons. RESULTS: We found that VPA promotes neurite outgrowth and prevents cell death in SH-SY5Y cells, but has no effect on cell proliferation. This neurotrophic effect does not involve inhibition of glycogen synthase kinase-3, histone deacetylase or prolyl oligopeptidase; the effect also does not seem to involve protein kinase C. In contrast, VPA activates ERK/MAPK and the survival effect of VPA is blocked by inhibition of the ERK/MAPK signalling pathway. Moreover, other activators of ERK/MAPK, such as epidermal growth factor and phorbol 12-myristate 13-acetate, mimic the neurotrophic effects of VPA. Other mood stabilizers do not activate ERK/MAPK and do not promote neurite outgrowth or survival of SH-SY5Y cells. In contrast, both lithium and VPA activate ERK/MAPK in rat primary cortical neurons. CONCLUSIONS: We investigated four mood stabilizers that are effective in the treatment of bipolar disorder. Our results suggest that, while some mood stabilizers may have additional neuroprotective effects, activation of ERK/MAPK does not appear to be a mechanism common to all mood-stabilizing drugs.

Animals↗
PubMed1999

A comparative analysis of the citrate permease P mRNA stability in Lactococcus lactis biovar diacetylactis and Escherichia coli.

The role of ribonucleases in the control of gene expression remains unknown in lactic acid bacteria. In the present work, we analysed the expression of the citP gene, which encodes the lactococcal citrate permease P, through the stability of the citQRP messenger in both Lactococcus lactis biovar diacetylactis (L. diacetylactis) and Escherichia coli. The chemical half-life for citQRP mRNA observed in L. diacetylactis wild-type strain was abnormally long for bacteria. It was even longer than that detected in E. coli RNase E or RNase III mutant strains. A model of processing and fate of RNA species containing citP gene is presented.

Bacterial Proteins↗
PubMed1977

Derivatization to stabilize some aliphatic primary hydroxylamines for g.l.c. analysis.

By appropriate choice of trimethylsilylating and trifluoroacetylating reagents and organic solvents for extraction, stable derivative of aliphatic primary hydroxylamines metabolites, N-hydroxyphentermine, N-hydroxychlorphentermine, N-hydroxymexiletene, N-hydroxyphenethylamine, N-hydroxyamphetamine, and N-hydroxy-3,4-dimethoxyamphetamine, were obtained and examined by g.l.c. analysis without decomposition and without interference from the parent drug or other metabolic products.

Amines↗

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