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PubMed1997

The transition to adulthood for youth who have serious emotional disturbance: developmental transition and young adult outcomes.

This article reviews studies that depict the developmental transition from adolescence to young adulthood of persons who have experienced serious emotional disturbance (SED) as children or adolescents. The literature demonstrates that their plight in young adulthood is grave. Youth with SED enter the transition phase delayed in their developmental maturation and face additional challenges relative to their nondisabled peers. As a group, they are undereducated, underemployed, and have limited social supports. Homelessness, criminal activity, and drug use are prevalent. This article defines the transitional youth population, describes the developmental tasks of transition, and summarizes the results of longitudinal studies that have tracked functional outcomes of transitional youth into young adulthood. The discussion focuses on the relevance of these findings to service provision.

Adolescent↗
PubMed1986

Inverted micellar intermediates and the transitions between lamellar, cubic, and inverted hexagonal amphiphile phases. III. Isotropic and inverted cubic state formation via intermediates in transitions between L alpha and HII phases.

Inverted cubic and isotropic phases have been observed in phospholipid and glycolipid systems. These phases exhibit characteristic morphologies in freeze-fracture electron micrographs, isotropic 31P-NMR resonances and (in some cases) cubic X-ray diffraction patterns. It is proposed here that these phases may form from the same intermediates that are involved in lamellar/inverted hexagonal (L alpha/HII) phase transitions, and that it is possible that these cubic and isotropic phases are metastable. According to a kinetic theory of L alpha/HII phase transitions, intermediates in such transitions can form structures known as interlamellar attachments (ILAs). It is shown that ILAs should form in large numbers during L alpha/HII transitions in systems like those reported to form inverted cubic or isotropic structures. ILAs cannot readily assemble into either the HII phase or well-ordered arrays of L alpha phase bilayers, and represent a kinetic trap for intermediates in L alpha/HII transitions (although it is possible that they are marginally more stable in a thermodynamic sense than the L alpha phase in a small temperature range below TH). It is also shown that arrays of ILAs should form metastable arrays with the same morphology and isotropic 31P-NMR resonances that are observed in isotropic and inverted cubic states. In particular, under some circumstances ILAs will assemble into a structure identical to the bicontinuous inverted cubic phase previously described in monoglycerides and very similar in morphology to structures observed in phospholipid systems. Finally, since isotropic and cubic states form from ILAs, which also can mediate fusion of unilamellar vesicles, unilamellar vesicles should fuse to at least some extent under the same conditions in which multilamellar samples of the same lipid form isotropic or inverted cubic states. This correlation has been observed.

Glycolipids↗
PubMed1993

Phase transitions of Acholeplasma laidlawii membranes. The involvement of Mg(2+)-ATPase in the C transition.

Highly sensitive differential scanning calorimetry has been employed to study the phase transitions of A. laidlawii membrane. The DSC curves obtained show five distinct transitions between 20 and 80 degrees C which contain a reversible lipid thermotropic transition at about 37 degrees C and four irreversible denaturation transitions of the membrane proteins occurred at about 44 degrees C, 52 degrees C, 62 degrees C, and 67 degrees C, respectively. Total enthalpy of the thermal denaturation of membrane proteins is 3.4 +/- 0.5 cal/g. Further study of A. laidlawii membrane preparations by means of thermal gel analysis and enzyme activity measurements at various temperatures provided information that the third peak (C transition) of the DSC curve involved primarily with Mg(2+)-ATPase on A. laidlawii membranes.

Acholeplasma laidlawii↗
PubMed2004

The use of dynamic vapour sorption and near infra-red spectroscopy (DVS-NIR) to study the crystal transitions of theophylline and the report of a new solid-state transition.

This study was undertaken to see if the combined technique of DVS-NIR could add to the understanding of transitions between physical forms of theophylline. There was excellent correlation between the mass changes and the intensity of the NIR peaks, showing that the hydrate was being formed and lost. This was characterised by the peaks at 1478 and 1972 nm representing an -OH deformation. NIR spectra for desorption shows that the dehydrate retains partial structure of both the anhydrate and hydrate crystal lattices. During rehydration of the dehydrate a new transition was discovered. An unexpected mass loss occurred between 40 and 50% RH. Usually, a mass loss during water sorption is characteristic of crystallisation of an amorphous material, although in this case it could be that the sample is crystalline. NIR data showed that during this transition the dehydrate peaks reverted back to the peak positions seen for anhydrous theophylline. The absorption of water into the dehydrate allowed the freedom of movement for the stable anhydrous lattice to form. It was concluded that DVS-NIR is a useful tool to study solid-state transitions and that the transition exists for conversion of theophylline dehydrate to anhydrate which is facilitated through water sorption.

Crystallization↗
PubMed2006

Do proteins with similar folds have similar transition state structures? A diffuse transition state of the 169 residue apoflavodoxin.

Apoflavodoxin from Anabaena PCC 7119 is a 169 residue globular protein of known structure and energetics. Here, we present a comprehensive Phi-value analysis to characterize the structure of its transition state. A total of 34 non-disruptive mutations are made throughout the structure and a range of Phi-values from zero to one are observed. In addition, a small set of eight aliphatic small-to-large mutations have been introduced in the hydrophobic core of the protein and they have been analyzed to investigate the feasibility of stabilizing the unfolding transition state by creating new non-native interactions. We find that the transition state of apoflavodoxin (so far the largest protein subjected to Phi-analysis) is diffuse and that it can be stabilized by unspecific hydrophobic interactions that can speed up the folding reaction. The data gathered on the apoflavodoxin transition state are compared with results from experimental studies in other proteins to revisit the relationship between the native state topology and transition state structure.

Anabaena↗
PubMed2006

Electrostatic interactions in the denatured state and in the transition state for protein folding: effects of denatured state interactions on the analysis of transition state structure.

The development of electrostatic interactions during the folding of the N-terminal domain of the ribosomal protein L9 (NTL9) is investigated by pH-dependent rate equilibrium free energy relationships. We show that Asp8, among six acidic residues, is involved in non-native, electrostatic interactions with K12 in the transition state for folding as well as in the denatured state. The perturbed native state pK(a) of D8 (pK(a) = 3.0) appears to be maintained through non-native interactions in both the transition state and the denatured state. Mutational effects on the stability of the transition state for protein (un)folding are often analyzed in respect to change in ground states. Thus, the interpretation of transition state analysis critically depends on an understanding of mutational effects on both the native and denatured state. Increasing evidence for structurally biased denatured states under physiological conditions raises concerns about possible denatured state effects on folding studies. We show that the structural interpretation of transition state analysis can be altered dramatically by denatured state effects.

Hydrogen-Ion Concentration↗
PubMed1986

Inverted micellar intermediates and the transitions between lamellar, cubic, and inverted hexagonal lipid phases. I. Mechanism of the L alpha----HII phase transitions.

A model for the thermotropic transitions between lamellar (L alpha) and inverted hexagonal (HII) phases is developed. According to this model, the first structures to form during the L alpha----HII transition are inverted micellar intermediates (IMI). The structure, formation rates, and half-lives of IMI ("lipidic particles") were described previously. IMI coalesce in the planes between apposed bilayers to form two types of HII phase precursors. The first is a monolayer-encapsulated HII tube (RMI), which forms via coalescence of IMI in pearl-string fashion. These structures have been proposed previously based on electron microscopic evidence. I show that if only RMI form, L alpha in equilibrium HII transitions cannot occur on observed time scales (faster than seconds). I propose that a second type of intermediate, a line defect (LD), forms as well. LD should form via IMI-IMI coalescence in significant numbers, and elongate rapidly into structures consisting of two apposed halves of HII tubes. Transitions via LD can occur in less than seconds, the time depending on the fraction of IMI-IMI coalescence events producing LD and the number of IMI per unit of bilayer area. Hysteresis in the phase transition temperature may be due to the difference in water content of the two phases and their low water permeabilities. The model is in qualitative agreement with morphological, NMR, and x-ray diffraction data on phospholipid systems. The results are relevant to IMI-mediated interactions between unilamellar bilayer vesicles, and to the structure of inverted cubic phases observed in some phospholipid systems. These will be discussed in subsequent publications (D. P. Siegel, manuscript in preparation).

Colloids↗
PubMed2000

New probes of the F1-ATPase catalytic transition state reveal that two of the three catalytic sites can assume a transition state conformation simultaneously.

MgADP in combination with fluoroscandium (ScFx) is shown to form a potently inhibitory, tightly bound, noncovalent complex at the catalytic sites of F(1)-ATPase. The F(1).MgADP.ScFx complex mimics a catalytic transition state. Notably, ScFx caused large enhancement of MgADP binding affinity at both catalytic sites 1 and 2, with little effect at site 3. These results indicate that sites 1 and 2 may form a transition state conformation. A new direct optical probe of F(1)-ATPase catalytic transition state conformation is also reported, namely, substantial enhancement of fluorescence emission of residue beta-Trp-148 observed upon binding of MgADP.ScFx or MgIDP. ScFx. Using this fluorescence signal, titrations were performed with MgIDP.ScFx which demonstrated that catalytic sites 1 and 2 can both form a transition state conformation but site 3 cannot. Supporting data were obtained using MgIDP-fluoroaluminate. Current models of the MgATP hydrolysis mechanism uniformly make the assumption that only one catalytic site hydrolyzes MgATP at any one time. The fluorometal analogues demonstrate that two sites have the capability to form the transition state simultaneously.

Adenosine Diphosphate↗
PubMed1985

Protein structural changes accompanying formation of enzymatic transition states: tryptophan environment in ground-state and transition-state analogue complexes of adenosine deaminase.

The accessibility of protein tryptophan fluorescence to the quenching agent acrylamide has been studied in adenosine deaminase and in binary complexes of the enzyme with ground-state or transition-state analogues. Although the enzyme contains three tryptophan residues, Stern-Volmer plots are linear with all the fluorescence quenchable at high acrylamide concentrations. Tryptophan fluorescence is less easily quenched in the binary complexes than in the free enzyme, indicating a decrease in the accessibility of these residues. The greatest decrease in accessibility is found for the transition-state analogue complexes. Although the affinities of the transition-state analogues studied span a range of 10(6), the Stern-Volmer constants of the complexes are the same within experimental error. Thus, as measured by this technique, changes in enzyme conformation accompanying formation of these complexes are similar for all transition-state analogues. Resonance energy transfer from tryptophan as donor to ligand as acceptor successfully explains the differing abilities of ligands to quench the enzyme's intrinsic fluorescence upon formation of complexes in the absence of acrylamide. On the basis of Forster distance calculations, it is likely that the residues partially quenched upon formation of transition-state analogue complexes are distant from the active site.

Adenosine Deaminase↗
PubMed2005

Crystallographic evidence for a new ensemble of ligand-induced allosteric transitions in hemoglobin: the T-to-T(high) quaternary transitions.

A detailed description of hemoglobin cooperativity requires knowledge of the dimer-dimer interactions responsible for the low ligand affinity of the quaternary-T tetramer, the "quaternary-T constraints", along with stereochemical pathways that specify how ligand binding disrupts these quaternary constraints. The recent mutagenic screen of Noble et al. [Noble, R. W., et al. (2001) Biochemistry 40, 12357-12368] has identified the major region of quaternary constraint to be a cluster of residues at the alpha1beta2 interface that is centered at Trp37beta. In this paper, crystallographic studies are presented for most of the mutant hemoglobins studied by Noble et al. These crystallographic experiments identify structural transitions-referred to as T-to-T(High) transitions-between the quaternary-T structure of wild-type deoxyhemoglobin and an ensemble of related T-like quaternary structures that are induced by some mutations in the Trp37beta cluster and/or by exposing crystals of wild-type or mutant deoxyhemoglobins to oxygen. The T-to-T(High) quaternary transitions consist of a rotation of the alpha1beta1 dimer relative to the alpha2beta2 dimer as well as a coupled alphabeta dimer bending component that consists of a small rotation of the alpha1 subunit relative to the beta1 subunit (and a symmetry related rotation of the alpha2 subunit relative to the beta2 subunit). In addition, differences in subunit tertiary structure associated with the T-to-T(High) transitions suggest two stereochemical pathways (one associated with the alpha subunits and one associated with the betasubunits) by which ligand binding specifically disrupts quaternary constraints in the Trp37beta cluster. In the alpha subunits, ligand binding induces a shift of the heme iron producing tension in a chain of covalent bonds that extends from the Fe-N(epsilon)(2)His(F8)alpha1 bond to the peptide backbone bonds of residues His87(F8)alpha1 and Ala88(F9)alpha1. This tension induces an alpha-to-pi transition in the COOH-terminal end of the F-helix that shifts the beta-carbon of Ala88alpha1 by approximately 1.5 A directly into the side chain of Tyr140alpha1 (a key residue in the Trp37beta2 cluster). Collectively these structural changes constitute a relatively short pathway by which ligand binding forces Tyr140alpha1 into the alpha1beta2 interface disrupting quaternary constraints associated with the Trp37beta2 cluster. In the beta subunits, our analysis suggests a more extended energy transduction pathway in which ligand-induced beta1-heme movement triggers tertiary changes in the beta1 subunit that promote alpha1beta1 dimer bending that disrupts quaternary constraints in the Trp37beta2 cluster at the alpha1beta2 interface.

Allosteric Regulation↗
PubMed2005

Optimized spin crossings and transition states for short-range electron transfer in transition metal dimers.

Electron-transfer reactions in eight mixed-valence manganese dimers are studied using B3LYP. One of the dimers is a model of the active site of manganese catalase, while another represents a basic building block of the oxygen-evolving complex in photosystem II. The adiabatic reactions are characterized by fully optimized transition states where the single imaginary frequency represents the electron-transfer coordinate. When there is antiferromagnetic coupling between different high-spin centers, electron transfer must be accompanied by a spin transition. Spin transitions are characterized by minimum-energy crossing points between spin surfaces. Three reaction mechanisms have been investigated. First, a single-step reaction where spin flip is concerted with electron transfer. Second, an initial transition to a center with intermediate spin that can be followed by electron transfer. Third, an initial transition to a ferromagnetic state from which the electron can be transferred adiabatically. The complexes prefer the third route with rate-determining barriers ranging from 5.7 kcal/mol to 17.2 kcal/mol for different complexes. The origins of these differences are discussed in terms of oxidation states and ligand environments. Many DFT functionals overestimate charge-transfer interactions, but for the present complexes, the error should be limited because of short Mn-Mn distances.

Dimerization↗
PubMedDate not supplied

[Phase transition studies of model and biological membranes. I. Use of hydrophobic fluorescent probes for studying phase transitions in liposomes].

Phase transition induced by temperature changes in liposomes prepared from synthetic dimyristoyl-(DML), dipalmytoyl-(DPL) and distearyl-(DSL) lecithins and also from equimolar mixture of DML and DPL and mixtures of DPL and cholesterol were studied with fluorescent probes such as 3-metoxybenzantron (MBA) and dimetylaminocholkone (DMC). The significant changes of fluorescence intensity and maximum position of MBA and DMC were found in the regions of phase transitions at 23, 42, 54 and 31c in liposomes from DML, DPL, DSL and mixture of DML and DPL, respectively. Cholesterol incorporation into liposomes from DPL led to a decrease of transition temperature and cooperativity for these liposomes. At cholesterol concentration of 20 mol. percent or more the transition disappeared completely. It is concluded that MBA and DMC can be used for the investigation of biological membranes phase transitions.

Cholesterol↗
PubMed2003

Effect of water potential on sol-gel transition and intermolecular interaction of gelatin near the transition temperature.

The sol-gel transition of gelatin, measured by thermal analysis and viscosity measurement, was analyzed in terms of the change in hydration state of polymer molecules. A new thermodynamic model was proposed in which the effect of water potential is explicitly taken into account for the evaluation of the free energy change in the sol-gel transition process. Because of the large number of water molecules involved and the small free energy change in the transition process, the contribution of water activity, a(W), was proved to be not negligible in the sol-gel transition process in solutions containing such low-molecular cosolutes as sugars, glycerol, urea, and formamide. The gel-stabilization effect of sugars and glycerol was linear with a(W), which seemed consistent with the contribution of water potential in the proposed model. The different stabilization effect among sugars and glycerol was explained by the difference in solvent ordering, which affects hydrophobic interaction among protein molecules. The gel-destabilization effect of urea and formamide could be explained only by the direct binding of them to protein molecules through hydrogen bonding. On the contrary, the polymer-polymer interaction, measured by the viscosity analysis, in polyethyleneglycol and dextran solutions was not sensitive to the change in a(W), suggesting that no substantial change in hydration state with a(W) occurred in these polymer solutions.

Animals↗
PubMed2001

Clinical study of transitional cell carcinoma of the prostate associated with bladder transitional cell carcinoma.

BACKGROUND: Transitional cell carcinoma of the prostate in patients with bladder cancer appears to influence the prognosis and affects the decision about therapeutic modality. Therefore, it is important to characterize transitional cell carcinoma associated with bladder cancer. METHODS: From April 1980 to December 1998, 81 male patients underwent total cystoprostatectomies for transitional cell carcinoma of the bladder. The 81 cystoprostatectomy specimens were examined to clarify the characteristics of prostatic involvement by transitional cell carcinoma. The extent, origin, mode of spread and risk factor of prostatic involvement as well as the prognosis were investigated. In 13 of 15 patients with prostatic involvement the prostate was examined by sequential step sections. RESULTS: Prostatic involvement was observed in 15 of 81 patients (18.5%). Prostatic urethral involvement, invasion to prostatic duct/acinus, prostatic stromal invasion and extraprostatic extension and/or seminal vesicle involvement were recognized in 12 (80%), 14 (93.3%), six (40%), and five (33.3%) of the 15 patients, respectively. Twelve of the 15 patients (80%) with prostatic involvement had papillary or non-papillary tumors (i.e. carcinoma in situ) both in the prostatic urethra and prostatic duct. In 10 of these 12 patients (88.3%), there was contiguity between prostatic urethral and ductal tumors. Seven of the 23 patients (30.4%) with carcinoma in situ of the bladder showed prostatic involvement, which increased to 50% in the presence of carcinoma in situ of the trigone or bladder neck. CONCLUSIONS: Eighty per cent of the patients with prostatic involvement showed papillary or non-papillary tumors both in the prostatic urethra and prostatic duct. There was a high level of contiguity between both tumors. Patients with carcinoma in situ of the trigone or bladder neck revealed significantly higher incidence of prostatic involvement.

Carcinoma in Situ↗
PubMed2004

Transition path sampling study of flip-flop transitions in model lipid bilayer membranes.

The microscopic dynamics of lipids in biomembranes is of special relevance in the study of chemical reactions produced in cells. The mechanism of the exchange of a model lipid molecule between both sides of a flexible bilayer membrane or flip-flop in an aqueous environment has been studied by computer simulation using the recently developed transition path sampling technique, since flip-flop transitions are infrequent events of the lipid dynamics. In addition, structural changes in the membrane have been investigated at ambient conditions and for increasing temperature. Our results highlight the cooperative effort of the whole system in order to allow a lipid molecule to cross the bottleneck in configuration space associated with the transition state of the flip-flop event. Within the time interval of the transition, all molecules of the system significantly change the frequency of their molecular motions.

Computer Simulation↗
PubMed1987

Idiopathic slow-transit constipation: whole gut transit times, measured by a new simplified method, are not shortened by opioid antagonists.

A simplified method for measuring mean whole gut transit time has been validated which avoids stool collection and is suitable for out-patients. Radio-opaque markers are swallowed daily for 14 days and the mean whole gut transit time is derived directly from an abdominal X-ray. Using this new technique, neither nalmefene (in a double-blind study of six patients) nor naloxone (in an open study of four patients) shortened mean whole gut transit time in idiopathic slow-transit constipation.

Adult↗
PubMed1985

Role of topological constraints in the all-or-none transition of a globular protein model: theory of the helix-coil transition in doubly crosslinked, coiled coils.

Employing a recently developed statistical mechanical theory, the alpha-helix-to-random-coil transition in two-chain, coiled coils is shown to possess many of the essential qualitative features of the equilibrium folding process in globular proteins. The role of short vs. long range interactions in stabilizing the native structure is examined. We demonstrate in doubly crosslinked coiled coils how, due to the role of loop entropy, an intrinsically continuous conformational transition evolves into one well approximated by an all-or-none transition. Thus the present work points out the crucial role played by loop entropy in the conformational transition in coiled coils in particular and perhaps in globular proteins in general.

Models, Chemical↗
PubMed2000

Thermal transitions in the bilayer assembly of dimyristoylphosphatidylglycerol sodium salt dispersion in water: a new phase transition through an intermediate state.

The thermal properties of the dispersion of sodium salt of dimyristoylphosphatidylglycerol (NaDMPG) in water have been investigated as functions of incubation temperature and aging time by DSC, XRD, sodium ion activity, pH, zeta-potential, and IR measurements. The DSC charts for NaDMPG dispersions incubated below 30 degrees C showed an endothermic peak at 31.7 degrees C with a small shoulder peak at Tm (gel-liquid crystal transition temperature: 23.5 degrees C). The temperature of 31.7 degrees C coincides with the T* temperature at which a high-order transition in the NaDMPG bilayer assembly has been found to occur in our previous studies. However, no peak was observed for the dispersions incubated above 32 degrees C. These results indicate that thermal properties of NaDMPG bilayers definitely differ below and above the T* temperature. The dispersion which had been once incubated at 40 degrees C for 24 h never showed the endothermic peak at T* even after the further aging at 3 degrees C for 12-day. Namely, the NaDMPG bilayer assembly exhibits an intensive thermohysteresis. The XRD charts for the NaDMPG dispersions incubated at 25 degrees C showed a sharp X-ray diffraction pattern corresponding to the repeat distance of d = 4.75 nm regardless of their aging time, while the dispersions incubated at 40 degrees C had no diffraction peak until 9-day elapsed. After 10-day aging at 40 degrees C, however, a diffraction peak corresponding to d = 5.55 nm clearly appeared. In the DSC measurements for the dispersion incubated at 40 degrees C, a few endothermic peaks began to appear between Tm and T* after approximately 7-day aging. Then, they shifted toward higher temperatures and finally converged into a single peak at 40-42 degrees C after 14-day aging. These XRD and DSC peaks observed after a long period of aging time above T* suggest that conformations of the hydrophilic groups and the hydrocarbon chains in the NaDMPG bilayers take a more tight and closer arrangement very slowly via an intermediate state above T*, and a new gel phase of the bilayers is consequently formed, the transition temperature (T(I) temperature) of which is 40-42 degrees C. A molecular interpretation for such transition processes in the bilayer assembly of NaDMPG dispersions has been proposed on the basis of pH, sodium ion activity, zeta-potential, IR data, etc.

Calorimetry, Differential Scanning↗