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PubMed2001

Dissociations of the night: individual differences in sleep-related experiences and their relation to dissociation and schizotypy.

The author examined the associations among sleep-related experiences (e.g., hypnagogic hallucinations, nightmares, waking dreams, and lucid dreams), dissociation, schizotypy, and the Big Five personality traits in 2 large student samples. Confirmatory factor analyses indicated that (a) dissociation and schizotypy are strongly correlated-yet distinguishable-constructs, and (b) the differentiation between them can be enhanced by eliminating detachment/depersonalization items from the dissociation scales. A general measure of sleep experiences was substantially correlated with both schizotypy and dissociation (especially the latter) and more weakly related to the Big Five. In contrast, an index of lucid dreaming was weakly related to all of these other scales. These results suggest that measures of dissociation, schizotypy, and sleep-related experiences all define a common domain characterized by unusual cognitions and perceptions.

Adult↗
PubMed2006

Dissociation among Swedish adolescents and the connection to trauma: an evaluation of the Swedish version of Adolescent Dissociative Experience Scale.

The purpose of this study was to investigate the psychometric properties of the Swedish version of Adolescent Dissociative Experience Scale (A-DES), dissociative symptoms among Swedish adolescents, and dissociative symptoms connected to trauma and sexual and physical abuse. A normative group of 400 adolescents aged 12 to 19 years and a clinical group of 20 adolescents with known experienced trauma were given A-DES. A test-retest procedure was conducted with 90 subjects from the normative group. The results showed good reliability, internal consistency and test-retest. Factor analysis in the normative sample (N = 400) resulted in a one factor solution. Correlation between A-DES and other measures of dissociation was high (r = .86). Significant differences for the total sum of A-DES were found in the normative group between adolescents with and without self-reported trauma and between the normative group and the clinical group with known experienced trauma. The Swedish version of A-DES was shown to be a screening instrument with satisfactory psychometric qualities and the capability of capturing dissociative symptoms in adolescents with self-reported trauma as well as clinical cases with identified trauma.

Adolescent↗
PubMed2006

The dissociative processing style:a cognitive organization activated by perceived or actual threat in clinical dissociators.

This paper proposes a cognitive organization that operates during times of perceived or actual threat in individuals with dissociative psychopathology. This organization, referred to as the dissociative processing style (DPS), serves as a threat monitoring system. It is characterized by (1) a shift from selective attention processing to multiple streams of information processing, (2) weakened cognitive inhibitory functioning which allows these streams to be operational and (3) the directing of awareness towards some and away from other information streams. Whilst DPS activation has the potential for adaptive and protective functions, it also heightens the likelihood of dissociative symptom experience and dissociation itself. Dissociation is understood as a failure to integrate encoded information from multiple input streams. The DPS is argued to be activated by top-down processes which signal danger, such as the appraisal of contextual cues. A clinical example is used to highlight the characteristics of the DPS.

Adult↗
PubMed1998

[Questionnaire on dissociative symptoms. German adaptation, reliability and validity of the American Dissociative Experience Scale (DES)].

The "Fragebogen zu dissoziativen Symptomen (FDS)" represents the authorised German translation and adaptation of the "Dissociative Experience Scale" (DES; Bernstein and Putnam 1986). The original scale comprises 28 items covering dissociative experiences with regard to memory, identity, awareness and cognition according to DSM-III-R and DSM-IV. For the German version, 16 items were added to cover dissociative phenomena according to ICD-10, mainly pseudoneurological conversion symptoms. Reliability and validity of the German version were studied in a total sample of 813 persons and were compared to the results of the original version. Test-retest reliability of the FDS was rtt = 0.88 and Cronbach's consistency coefficient was alpha = 0.93, which is comparable to the results of the DES. The instrument differentiates between different samples (healthy control subjects, students, unselected neurological and psychiatric inpatients, neurological and psychiatric patients with a dissociative disorder and schizophrenics). The FDS is an easily applicable, reliable and valid measure to quantify dissociative experiences.

Dissociative Disorders↗
PubMed2004

Infrared multiphoton dissociation (IRMPD) and collisionally activated dissociation of peptides in a quadrupole ion trap with selective IRMPD of phosphopeptides.

Dissociation of protonated peptides via infrared multiphoton dissociation (IRMPD) provides more extensive sequence information than is obtained with collisionally activated dissociation (CAD) in a quadrupole ion trap due to the lack of the CAD low m/z cutoff and the ability to form secondary and higher order fragments with the non-resonant photoactivation technique. In addition, IRMPD is shown to be useful for the selective dissociation of phosphopeptides over those which are not phosphorylated because the greater photon absorption efficiency of the phosphorylated peptides leads to their more rapid dissociation. Finally, the selectivity of the IRMPD technique for phosphorylated species in complex mixtures is confirmed with the analysis of a mock peptide mixture and a tryptic digest of alpha-casein.

Amino Acid Sequence↗
PubMed2007

Infrared multiphoton dissociation of the siderophore enterobactin and its Fe(III) complex. Influence of Fe(III) binding on dissociation kinetics and relative energetics.

The dissociation pathways of the siderophore enterobactin and its complex with Fe(III) were examined using infrared multiphoton dissociation (IRMPD). Under experimental conditions (pH = 3.5), both compounds' electrospray spectra exhibited exclusively singly-charged anions. The compositions of the dissociation products were characterized by accurate mass measurements using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The primary dissociation channel for both species was determined to be the loss of one serine group from the precursor molecules. To further investigate the influence of Fe(III) binding on the intramolecular interactions, dissociation kinetics and relative energetics for the loss of this serine group were determined using the focused radiation for gaseous multiphoton energy-transfer (FRAGMENT) method. From the kinetic data, it was found that enterobactin was approximately seven times more reactive than its Fe(III) complex over the range of laser intensities investigated. The relative activation energies, however, exhibited similar values, approximately 7 kcal.mol(-1). These results suggest that at pH = 3.5, Fe(III) interacts with only two of the three serine groups. The results from the present work are believed to be valuable for the characterization of novel siderophores as well as their associated metabolites and synthetic analogues.

Enterobactin↗
PubMed2003

Determination of the activation energy for unimolecular dissociation of a non-covalent gas-phase peptide: substrate complex by infrared multiphoton dissociation fourier transform ion cyclotron resonance mass spectrometry.

The activation energy for the unimolecular dissociation of a non-covalent supramolecular complex between an Artificial Cationic Receptor A ([Gua-Val-Val-Val-Amide]+, in which Gua is guanidiniocarbonyl pyrrole) and an Anionic Tetrapeptide B ([N-Acetyl-Val-Val-Ile-Ala]-) has been determined by measurement of the dissociation rate constant as a function of infrared CO2 laser power density. Singly-charged quasimolecular [A + B + H]+ ions are isolated, stored in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer, and irradiated by IR photons. The rate constant for dissociation of the non-covalent complex is determined at five different laser power densities. A plot of the natural logarithm of the first-order rate constant versus the natural logarithm of the laser power density yields a straight line, the slope of which provides an approximate measure of the activation energy (Ea(laser)) for dissociation. Ea(laser) is calculated by a relationship derived earlier by Dunbar and with a newly proposed equation by Paech et al. The results of the two approaches deliver significantly different activation energy values for the unimolecular dissociation of the non-covalent complex. We obtain EaI(laser) = 0.67 eV (Dunbar approximation) and EaII(laser) = 1.12 eV (Paech et al. approximation). Differences between the two approaches are discussed with respect to non-covalent complexes.

Bradykinin↗
PubMed1997

Dissociation of heme-globin complexes by blackbody infrared radiative dissociation: molecular specificity in the gas phase?

The temperature dependence of the unimolecular kinetics for dissociation of the heme group from holo-myoglobin (Mb) and holo-hemoglobin alpha-chain (Hb-alpha) was investigated with blackbody infrared radiative dissociation (BIRD). The rate constant for dissociation of the 9 + charge state of Mb formed by electrospray ionization from a "pseudo-native" solution is 60% lower than that of Hb-alpha at each of the temperatures investigated. In solutions of pH 5.5-8.0, the thermal dissociation rate for Mb is also lower than that of HB-alpha (Hargrove, M. S. et al. J. Biol. Chem.1994, 269, 4207-4214). Thus, Mb is thermally more stable with respect to heme loss than Hb-alpha both in the gas phase and in solution. The Arrhenius activation parameters for both dissociation processes are indistinguishable within the current experimental error (activation energy 0.9 eV and pre-exponential factor of 10(8-10) s(-1)). The 9+ to 12+ charge states of Mb have similar Arrhenius parameters when these ions are formed from pseudo-native solutions. In contrast, the activation energies and pre-exponential factors decrease from 0.8 to 0.3 eV and 10(7) to 10(2) s(-1), respectively, for the 9 + to 12 + charge states formed from acidified solutions in which at least 50% of the secondary structure is lost. These results demonstrate that gas-phase Mb ions retain clear memory of the composition of the solution from which they are formed and that these differences can be probed by BIRD.

Journal Article↗
PubMed1999

Dissociation energies of deoxyribose nucleotide dimer anions measured using blackbody infrared radiative dissociation.

The dissociation kinetics of deprotonated deoxyribose nucleotide dimers were measured using blackbody infrared radiative dissociation. Experiments were performed with noncovalently bound dimers of phosphate, adenosine (dAMP), cytosine (dCMP), guanosine (dGMP), thymidine (dTMP), and the mixed dimers dAMP.dTMP and dGMP.dCMP. The nucleotide dimers fragment through two parallel pathways, resulting in formation of the individual nucleotide or nucleotide + HPO3 ion. Master equation modeling of this kinetic data was used to determine threshold dissociation energies. The dissociation energy of (dGMP.dCMP-H)- is much higher than that for the other nucleotide dimers. This indicates that there is a strong interaction between the nucleobases in this dimer, consistent with the existence of Watson-Crick hydrogen bonding between the base pairs. Molecular mechanics simulations indicate that Watson-Crick hydrogen bonding occurs in the lowest energy structures of (dGMP.dCMP-H)-, but not in (dAMP.dTMP-H)-. The trend in gas phase dissociation energies is similar to the trend in binding energies measured in nonaqueous solutions within experimental error. Finally, the acidity ordering of the nucleotides is determined to be dTMP < dGMP < dCMP < dAMP, where dAMP has the highest acidity (largest delta Gacid).

Algorithms↗
PubMed2001

Thermal decomposition of a gaseous multiprotein complex studied by blackbody infrared radiative dissociation. Investigating the origin of the asymmetric dissociation behavior.

The blackbody infrared radiative dissociation technique was used to study the thermal decomposition of the gaseous B5 pentamer of the Shiga-like toxin I and its complexes with the Pk trisaccharide and a decavalent Pk-based oligosaccharide ligand (STARFISH, S). Dissociation of the protonated pentamer, (B5 + nH)n+ triple bond B5n+ where n = 11-14, proceeds almost exclusively by the loss of a single subunit (B) with a disproportionately large fraction (30-50%) of the parent ion charge. The degree of charge enrichment of the leaving subunit increases with increasing parent ion charge state. For n = 12-14, a distribution of product ion charge states is observed. The yields of the complementary pairs of product ions are sensitive to the reaction temperature, with higher temperatures favoring greater charge enrichment of the leaving subunit for +13 and +14, and the opposite effect for +12. These results indicate that some of the protons are rapidly exchanged between subunits in the gas phase. Dissociation of B5(14+) x S proceeds exclusively by the loss of one subunit, although the ligand increases the stability of the complex and also reduces the degree of charge enrichment in the ejected monomer. For B5(12+)(Pk)1-3, the loss of neutral Pk competes with loss of a subunit at low temperatures. Linear Arrhenius plots were obtained from the temperature-dependent dissociation rate constants measured for the loss of B from B5n+ and B514+ x S. The magnitude of the Arrhenius parameters is highly dependent on the charge state of the pentamer: Ea = 35 kcal/mol and A = 1,019 s(-1) (+14), 46 kcal/mol and 1,023 S(-1) (+13), 50 kcal/mol and 1026 s(-1) (+12), and 80 kcal/mol and 10(39) (+11). The Ea and A for B5(14+) x S are 59 kcal/mol and 10(30) s(-1), respectively. The reaction pathways leading to greater charge enrichment of the subunit lost from the B5(14+) and B5(13+) ions correspond to higher energy processes, however, these pathways are kinetically preferred at higher temperatures due to their large A factors. A simple electrostatic model, whereby charge enrichment leads to Coulombic repulsion-induced denaturation of the subunits and disruption of the intersubunit interactions, provides an explanation for the magnitude of the Arrhenius parameters and the origin of the asymmetric dissociation behavior of the complexes.

Carbohydrate Sequence↗
PubMed1969

Dissociation of 70S ribosomes: some properties of the dissociating factor from Bacillus stearothermophilus and Escherichia coli.

A protein factor which produces in vitro dissociation of 70S particles into 30S and 50S subunits has been obtained from Bacillus stearothermophilus and Escherichia coli. The factor could be extracted from ribosomes, polyribosomes, and S100 supernatant. The kinetics and temperature curve of the dissociation process in the B. stearothermophilus system have been studied and compared with the reaction in the E. coli system. No species specificity was observed when hybrid mixtures of ribosomes and dissociating factor from both bacteria were used. The wide variations of dissociating activity in cells at different stages of growth and the capacity of the liberated subunits to carry out polypeptide synthesis suggest that the dissociating factor has a physiological role.

Bacillus↗
PubMed1996

Chloride effects on Gs subunit dissociation. Fluoroaluminate binding to Gs does not cause subunit dissociation in the absence of chloride ion.

The stimulatory guanine nucleotide binding protein (Gs) is heterotrimeric ( alpha beta gamma), and mediates activation of adenylyl cyclase by a ligand-receptor complex. The alpha subunit of Gs (Gsalpha) has a guanine nucleotide binding site, and activation occurs when tightly bound GDP is displaced by GTP. Together, GDP and fluoroaluminate (AlF4-) form a transition state analog of GTP that activates Gs. The work of other investigators suggests that AlF4- causes subunit dissociation when it activates Gs. We have observed that in solution AlF4- did not cause Gs subunits to dissociate unless NaCl was also present. The effect of NaCl was concentration dependent (10-200 mM). Omitting F-, Al3+, or Mg2+ prevented the NaCl-induced dissociation of Gs subunits. Na2SO4 could not substitute for NaCl in causing subunit dissociation, but KCl could, suggesting that the anion was responsible for the effect. Gs subunit reassociation occurred when the concentration of Cl- was reduced even though the concentrations of AlF4- and Mg2+ were maintained. The absence of Cl- did not prevent AlF4- binding to Gsalpha. We have concluded that AlF4-, a ligand which is capable of activating G proteins, can bind to Gs in solution without causing subunit dissociation.

Adenylyl Cyclases↗
PubMed2006

On-chip non-equilibrium dissociation curves and dissociation rate constants as methods to assess specificity of oligonucleotide probes.

Nucleic acid hybridization serves as backbone for many high-throughput systems for detection, expression analysis, comparative genomics and re-sequencing. Specificity of hybridization between probes and intended targets is always critical. Approaches to ensure and evaluate specificity include use of mismatch probes, obtaining dissociation curves rather than single temperature hybridizations, and comparative hybridizations. In this study, we quantify effects of mismatch type and position on intensity of hybridization signals and provide a new approach based on dissociation rate constants to evaluate specificity of hybridized signals in complex target mixtures. Using an extensive set of 18mer oligonucleotide probes on an in situ synthesized biochip platform, we demonstrate that mismatches in the center of the probe are more discriminating than mismatches toward the extremities of the probe and mismatches toward the attached end are less discriminating than those toward the loose end. The observed destabilizing effect of a mismatch type agreed in general with predictions using the nearest neighbor model. Use of a new parameter, specific dissociation temperature (T(d-w), temperature of maximum specific dissociation rate constant), obtained from probe-target duplex dissociation profiles considerably improved the evaluation of specificity. These results have broad implications for hybridization data obtained from complex mixtures of nucleic acids.

Base Pair Mismatch↗
PubMed2004

A comparative study of the collision induced dissociation and the electron capture dissociation of model peptides using ESI-FTMS.

Tandem mass spectra of several model peptides, including KG3WG3K, NG3WG3N, RG7R, RG3WG3R, RG3DG3R, RG3EG3R, RG3FG3R and RG5WG5R were studied using both SORI-CID and ECD methods. By cross comparing the fragmentation pattern of these peptides using the same dissociation method and the same peptide using different dissociation methods, interesting spectral features that are related to the mechanisms of dissociation under SORI-CID and ECD conditions were extracted. Both dissociation methods were believed to be charge-directed. Due presumably to the stepwise ion activation, peptide ion dissociation under SORI-CID conditions was influenced mainly by "localized" hydrogen bonds. Consistent with previous literature findings, mobility proton model could be used to account for the spectral features observed. Substantial changes in the fragmentation patterns of these peptides were observed by using ECD methods. By postulating that the initial tertiary structures of the peptide ions were retained prior to electron capture process, the changes in fragmentation pattern could be attributed to the directing effect of the "global" hydrogen-bonding network. From the present results, no special preference was observed for cleavage at the backbone linkages adjacent to tryptophan residue over other inter-residual linkages. The previous reported nine-times cleavage preference at the C-terminal side of the tryptophan residue should therefore be attributed to some sequence specific phenomena.

Amino Acid Sequence↗
PubMed2004

Relationship between the expression of extracellular signal-regulated kinase 1/2 and the dissociation of pancreatic cancer cells: Involvement of ERK1/2 in the dissociation status of cancer cells.

Mitogen-activated protein kinase kinase 2 (MEK2), the upstream kinase of extracellular signal-regulated kinase 1/2 (ERK1/2) was previously isolated as cancer cell dissociation related factor. In this study, to further clarify the regulatory mechanism of cancer cell dissociation, two hamster (PC-1.0 and PC-1) and human (Capan-2 and AsPC-1) pancreatic cancer cell lines were analyzed immunocytochemically with anti-ERK1, anti-ERK2 and anti-phosphorylated ERK1/2 (p-ERK1/2) antibodies. U0126 (a MEK1/2 inhibitor) significantly suppressed ERK2 and p-ERK1/2 expressions in PC-1.0 and AsPC-1 cells (P<0.05). Cancer cell dissociation factor (DF) markedly induced ERK2 and p-ERK1/2 expressions in PC-1 and Capan-2 cells (P<0.05), and the induced ERK2 and p-ERK1/2 expressions were inhibited by subsequent U0126-treatment (P<0.05). Simultaneously, light microscopic images showed that DF clearly induced cell dissociation in PC-1 and Capan-2 cells, while U0126-treatment induced cell aggregation in these pancreatic cancer cells. ERK2 activation is closely involved in cell dissociation of pancreatic cancer cells.

Animals↗
PubMed1996

Intellectual functioning of inpatients with dissociative identity disorder and dissociative disorder not otherwise specified. Cognitive and neuropsychological aspects.

The intellectual functioning of 105 inpatients with multiple personality disorder and dissociative disorder not otherwise specified was assessed using the Wechsler Adult Intelligence Scale-Revised as part of a comprehensive research protocol. There were no significant intellectual differences between the groups on any major intelligence quotient summary score or any of the age-adjusted empirical factor scores. The anecdotal but widely accepted hypotheses that dissociative patients either have above average premorbid intelligence or that their current intellectual functioning is deleteriously affected by their fluctuant psychiatric disorder were not supported in this sample. A significant subsample of the multiple personality disorder group manifested abnormal interest scatter on the Wechsler Adult Intelligence Scale-Revised verbal subtests, and this variability was attributed to subtle neuropsychological deficits on the Memory/Distractibility factor. We speculate that dissociative patients might need to be evaluated for attention deficit disorder in addition to the range of dissociative symptoms in a comprehensive evaluation.

Adult↗
PubMed2003

Investigating the construct validity of the dissociative taxon: stability analyses of normal and pathological dissociation.

Research has suggested the existence of a pathological dissociative taxon. However, relatively little is known about this taxon. This study examined the 2-month retest stability of this taxon--together with other measures of dissociation and the Big Five--in a sample of 465 undergraduates. Contrary to expectation, taxon scores were only modestly stable and were substantially less stable than the other measures, including continuous indicators of dissociation. Furthermore, most individuals who were identified as taxon members at one assessment were classified as nonmembers at the other. These results challenge the existence of a pathological dissociative taxon. More generally, these data demonstrate that statistically identified taxa need to be explicated through the normal process of construct validation.

Adult↗
PubMed1998

[Dissociation and schizophrenia. Schizophrenias--a dissociative nosopoietic construct?].

The historical roots of the nosopoietic construct schizophrenia are traced: the nosographic construction by Kraepelin, an act of unification and split at the same time. The name schizophrenia reflects the tradition of the model of dissociation which is aetiologically connected with the idea of weakness of the synthetic power of the psyche: psychasthenia. In the establishment of the supposed nosological entity schizophrenia, the name-giving idea of dissociation was almost forgotten. Thus, nowadays Dissociative Disorders are classified in ICD and DSM separately from schizophrenic disorders, but it must be borne in mind that the schizophrenic disorders represent the most severe of disorders, hypothetically based on dissociation, namely, fragmentation of the ego.

Dissociative Disorders↗