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At least 1,405 records · Page 78Linked to original sources
PubMed1992

Dynamic NMR spectral analysis and protein folding: identification of a highly populated folding intermediate of rat intestinal fatty acid-binding protein by 19F NMR.

The folding of intestinal fatty-acid binding protein has been monitored by 19F NMR after incorporation of 6-fluorotryptophan into the protein. The two resonances resulting from the two tryptophans of this protein showed different dependencies on denaturant concentration. One of the resonances was in slow chemical exchange between two resonance frequencies, native and completely unfolded. The changes for this resonance occurred over a denaturant concentration range identical to that monitored by circular dichroism or fluorescence during unfolding. The other resonance continued to show changes at concentrations of denaturant well above that needed to complete the unfolding transition as monitored by optical techniques. Site directed mutagenesis showed that tryptophan-82 was the residue responsible for the unexpected behavior. We conclude, based on complete line-shape analysis, that there are significant concentrations of one or more intermediates in equilibrium with the native and unfolded forms. The structure of the intermediate(s) is more similar to the completely unfolded form of the protein than to the native structure, since little if any secondary structure is present. Further, these structure(s) persist at high denaturant concentrations and may represent local initiating sites in the folding of this beta-sheet protein.

Amino Acid Sequence↗
PubMed2004

Electrocorticogram spectral analysis and somatosensory evoked potentials as tools to assess electrical stunning efficiency in ducks.

1. Fast Fourier transformations (FFTs) of electrocorticogram (ECoG) signals and averaging of somatosensory evoked potentials (SEPs) were used for assessing the impact of electrical stunning of ducks in a waterbath set to deliver a constant current of 150 mA, 600 Hz alternating current (AC) for 4 s. The effectiveness of stunning was determined on the basis of induction of epileptiform activity in the ECoG followed by a decrease in total power content to less than 10% of pre-stun values and abolition of SEPs. 2. One out of 10 birds was killed by the stun. FFT analysis of the ECoG signals of the remaining 9 birds showed that only one bird had a decrease of the total power to less than 10% of the pre-stun values for up to 70 s post-stun. The SEPs were retained in 6 out of 9 ducks and and 4 of them retained the evoked responses throughout the post-stun period. In the two birds showing abolition of SEPs, this was associated with a decrease in the total power content to below 10% of the pre-stun value. 3. The present experiment confirmed that the abolition of SEPs and the decrease of the total power below 10% of the pre-stun value for assessing unconsciousness after an electrical stunning in various species are also applicable to ducks. Based on this, it is concluded that electrical waterbath stunning of ducks using 150 mA of 600 Hz AC is ineffective.

Abattoirs↗
PubMed1993

Spectral analysis of corticomotor evoked potentials in spinal cord injury. Part 1. Acute studies.

A model of graded spinal cord injury using ischaemia has been developed by using balloon occlusion of the abdominal aorta in rabbits. This model has been used to test pharmacological agents thought to provide protection against spinal cord injury based on changes in corticomotor evoked potentials (CMEPs). These highly reproducible signals are percutaneously recorded from the spinal cord in response to cortical stimulation and accurately reflect the degree of residual spinal cord function. The present study focused on the power spectra of CMEPs to clarify alterations in post-injury signals. This added dimension of previously unreported CMEP analysis will augment future applications of the current model.

Acute Disease↗
PubMed1993

Spectral analysis of corticomotor evoked potentials in spinal cord injury. Part 2. Chronic studies.

Corticomotor evoked potentials (CMEPs) have been suggested to accurately reflect neurological function, particularly with regard to the integrity of the spinal cord. However, the utility of these potentials to evaluate graded, chronic injury has received little attention. Frequency analysis has been suggested by the authors to be a method of simplifying interpretation of these complex signals. Ischaemic spinal cord injuries were produced in rabbits causing mild, moderate, or severe neurological deficits. CMEPs were recorded before, during, immediately following, and three days after injury. Alterations in the features of the power spectra reflected the degree of neurological injury. CMEP power spectra may predict neurological outcome and augment currently used electrodiagnostic tests.

Animals↗
PubMed2002

Power spectral analysis of the shape of fMLP-stimulated granulocytes. A tool for the study of cytoskeletal organization under normal and pathological conditions.

fMLP (N-formyl-methionyl-leucyl-phenylalanine) is a powerful activator of granulocytes, eliciting different metabolic responses, such as generation of reactive oxygen species, production of arachidonic acid metabolites, and release of lysosomal enzymes. fMLP determines also a dramatic rearrangement of the actin cytoskeleton; under non-gradient conditions this entails characteristic alterations in cell shape (chemokinesis), while under gradient conditions it is instrumental in promoting cell migration up the gradient (chemotaxis). Here we analyze mathematically the cell contour of fMLP-stimulated human granulocytes stimulated with fMLP under non-gradient conditions, using the methods for study of stochastic series. The cell contours were drawn and divided into 200 segments of equal linear length and the angles between consecutive segments were computed. The derived series of angles were examined for autocorrelations and from the autocorrelation function the power spectrum was calculated. Our results show that the pattern of lamellipodial extensions of the cell membrane is not entirely randomly-designed, but it is partly regulated by deterministic components, as revealed by the presence of statistically significant periodicities. Soon after fMLP stimulation, the power spectrum of the cell contours exhibits a single distinct peak at frequency 0.07, indicating a prevalence of prominent lamellipodia, each one covering in the average 1/15 of the linearized cell contour. Some 30 min after fMLP stimulation the power spectrum becomes flatter (indicating a general decrement of the deterministic component), but still presents one single peak; the latter is shifted to the right (frequency 0.13), indicating the prevalence of less prominent and regular, but more numerous, protrusions, each one covering 1/20 to 1/30 of the cell contour.

Cytoskeleton↗
PubMed1984

A microprocessor based instrument for the spectral analysis of the EEG in anaesthesia.

An instrument for monitoring the frequency components contained in the electroencephalogram is described. The technique uses the fast Fourier transform which is implemented in a microprocessor controlled 'black box'. The control and display of the data are organised by a conventional microcomputer. The system is designed for use by practising anaesthetists in a district general hospital environment and is, therefore, inexpensive and simple to operate. The operation of the equipment is described and some limited results from early clinical trials are presented.

Anesthesia↗
PubMed2002

Experimental protein mixture for validating tandem mass spectral analysis.

Several methods have been used to identify peptides that correspond to tandem mass spectra. In this work, we describe a data set of low energy tandem mass spectra generated from a control mixture of known protein components that can be used to evaluate the accuracy of these methods. As an example, these spectra were searched by the SEQUEST application against a human peptide sequence database. The numbers of resulting correct and incorrect peptide assignments were then determined. We show how the sensitivity and error rate are affected by the use of various filtering criteria based upon SEQUEST scores and the number of tryptic termini of assigned peptides.

Amino Acid Sequence↗
PubMed1998

Spectrum: spectral analysis of phylogenetic data.

MOTIVATION: Spectrum is a new Macintosh and Microsoft Windows program designed to read in phylogenetic four-state or binary data in NEXUS format, and output the corresponding bipartition spectra. It can be used to find the tree whose expected spectrum is closest to the observed spectrum (the closest tree, Hendy, Discr, Math., 96, 51-58,. 1991).

Phylogeny↗
PubMed1995

Effects of propofol and thiopentone, and benzodiazepine premedication on heart rate variability measured by spectral analysis.

We studied the effects of temazepam premedication and induction of anaesthesia with thiopentone or propofol on the heart rate power spectrum in 47 patients undergoing elective minor surgery. Eighteen patients received temazepam 20 mg orally as premedication. There was a significant reduction in high frequency power and total power, and an increase in the ratio of low to high frequency power after induction of anaesthesia with either propofol or thiopentone. Patients who had received temazepam premedication had significantly greater low frequency, high frequency and total power than those who were not premedicated. There was no significant difference between premedicated and unpremedicated patients in the ratio of low to ventilatory frequency power.

Adult↗
PubMed1988

Liquid chromatographic and mass spectral analysis of N-substituted analogues of 3,4-methylenedioxyamphetamine.

The C1 to C3 N-alkyl, N,N-dimethyl, and N-hydroxy analogues of 3,4-methylenedioxyamphetamine (MDA) are identified by high performance liquid chromatographic (HPLC) and spectrometric techniques. The compounds are separated using reversed-phase procedures on C18 stationary phase with an acidic (pH 3) aqueous methanol mobile phase. The mass spectra of the compounds are distinctive and reference spectra are provided. The N-hydroxy derivative is unstable at high temperatures and decomposes to MDA and the oxime of 3,4-methylenedioxyphenyl-2-propanone.

3,4-Methylenedioxyamphetamine↗
PubMed1989

Liquid chromatographic and mass spectral analysis of 1-(3,4-methylenedioxyphenyl)-3-butanamines, homologues of 3,4-methylenedioxyamphetamines.

The 1-(3,4-methylenedioxyphenyl)-3-butanamines (HMDAs) are prepared via reductive amination of the corresponding ketone with a series of low molecular weight alkylamines. These amines are homologues of the N-substituted 3,4-methylenedioxyamphetamines (MDAs). Compounds of the HMDA series have UV absorption properties similar to the MDAs because both series contain the same 3,4-methylenedioxyphenyl chromophore. The HMDAs are separated via reversed-phase liquid chromatographic methods using a C18 stationary phase and an acidic aqueous acetonitrile mobile phase. The mass spectra of these potential designer drugs are very similar to the spectra of the MDA homologues having the same N-substituent.

3,4-Methylenedioxyamphetamine↗
PubMed1990

Liquid chromatographic and mass spectral analysis of 1-(3,4-methylenedioxyphenyl)-1-propanamines: regioisomers of the 3,4-methylenedioxyamphetamines.

The title 1-(3,4-methylenedioxyphenyl)-1-propanamines represent positional isomers of the N-substituted 3,4-methylenedioxyamphetamines, clandestinely produced drugs frequently encountered by forensic laboratories. These propanamines are prepared by reductive amination of 3,4-methylenedioxypropiophenone with a series of N-alkylamines. Analytical methods are developed to distinguish these compounds from the MDA series. The ultraviolet spectra of the propanamines are very similar to those of the MDAs with absorption maxima at 284 and 236 nm. The propanamines are separated under reversed-phase liquid chromatographic conditions by using a C18 stationary phase and a mobile phase of acidic (pH 3) acetonitrile containing methanol and triethylamine. The relative retention properties of these compounds parallel those observed in the MDA series. The electron impact mass spectra of the propanamines are determined by GC-MS, and the fragmentation pattern clearly distinguishes these compounds from those of the MDA series having the same molecular weight.

3,4-Methylenedioxyamphetamine↗