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Results for “Structural validation”

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At least 253 records · Page 14Linked to original sources

PubMed2000

Validation of protein crystal structures.

Since the process of building and refining a model of a biomacromolecule based on crystallographic data is subjective, quality-control techniques are required to assess the validity of such models. During the 1990s, much experience was gained; the methods used and some of the lessons learned are reviewed here. In addition, an extensive compendium of quality criteria and quality-control methods that are or have been used to validate models of biomacromolecules has been compiled. The emphasis in this compendium is on the validation of protein crystal structures.

Biochemistry↗

PubMed1991

Cross-validation of the factor structure of the Aberrant Behavior Checklist for persons with mental retardation.

The original factor structure of the Aberrant Behavior Checklist was cross-validated with an American sample of 470 persons with moderate to profound mental retardation, including nonambulatory individuals. The results of the factor analysis with varimax rotation essentially replicated previous findings, suggesting that the original five factors (Irritability, Lethargy, Stereotypic Behavior, Hyperactivity, and Inappropriate Speech) could be cross-validated by factor loadings of individual items. The original five scales continue to show high internal consistency. These factors are easily interpretable and should continue to provide valuable research and clinical information.

Adult↗

PubMed1997

A validational study of the Structured Interview of Symptoms Associated with Sexual Abuse (SASA) using three samples of sexually abused, allegedly abused, and nonabused boys.

OBJECTIVE: With the rapid rise of sexual abuse allegations, there is a growing need to develop instruments to help clinicians determine the likelihood that sexual abuse has occurred. METHOD: This study evaluated the discriminant validity of a structured parent interview regarding emotional, behavioral, and physical symptoms by comparing results among three subsamples of age matched boys: 22 sexually abused boys whose perpetrator confessed, 47 boys evaluated in a sexual abuse clinic but without a history of perpetrator confession and 52 nonabused boys selected after rigorous screening. RESULTS: In comparison with the nonabused (NA) boys, the sexually abused boys were significantly more likely to demonstrate sudden emotional and behavioral changes, frequent stomach aches, more knowledge about sex and sexual activities than expected for age, unusual aggressiveness toward playmate or toy's private parts, crying easily, difficulty getting to sleep, and a change to poor school performance. The internal reliability of the SASA was determined to be .83 and scoring of an abbreviated 12-item scale demonstrated a sensitivity of 90.9% and a specificity of 88.5%. CONCLUSIONS: The findings suggest that Structured Interview of Symptoms Associated with Sexual Abuse (SASA) is an effective tool which may help in the comprehensive assessment of boys who may have been sexually abused.

Adolescent↗

PubMed2001

Complete cross-validation and R-factor calculation of a solid-state NMR derived structure.

Cross-validation of a solid-state NMR-derived membrane polypeptide structure is demonstrated. An initial structure has been achieved directly from solid-state NMR derived orientational restraints based on a variety of anisotropic nuclear spin interactions. Refining the molecular structure involves setting up a penalty function that incorporates all available solid-state NMR experimental data and an energy function. A validation method is required to choose the optimal weighting factor for the total penalty function to balance the contribution from the experimental restraints and the energy function. Complete cross-validation has been used to avoid over-fitting the orientational restraints. Such cross-validation involves partitioning of the experimental data into a test set and a working set followed by checking the free R-value during the refinement process. This approach is similar to the method used in crystallography and solution NMR. Optimizing the weighting factor on the penalty function by cross-validation will increase the quality of the refined structure from solid-state NMR data. The complete cross-validation and R-factor calculation is demonstrated using experimental solid-state NMR data from gramicidin A, a monovalent cation channel in lipid bilayers.

Journal Article↗

PubMed1990

Comparison of DSM-III and DSM-III-R diagnoses for prepubertal children: changes in prevalence and validity.

A structured and reliable diagnostic procedure based on a revised version of the Diagnostic Interview Schedule for Children for children, parents, and teachers was used to assign both DSM-III and DSM-III-R diagnoses to 177 outpatient boys aged 7 to 12 years. Compared to their DSM-III counterparts, DSM-III-R oppositional defiant disorder was 25.5% less prevalent, DSM-III-R dysthymia was 37.8% less prevalent, and DSM-III-R conduct disorder (CD) was 44.3% less prevalent. However, DSM-III-R attention deficit hyperactivity disorder was 14.4% more prevalent than DSM-III attention deficit disorder with hyperactivity. The two definitions of CD were compared to exemplify an empirical approach to diagnostic validation. The DSM-III-R diagnosis of CD appears to be more valid as it is more strongly associated with police contacts, school suspensions, and history of antisocial personality disorder in the biological father, but both CD diagnoses are associated with family histories of criminal convictions.

Child↗

PubMed1991

Reliability and validity of the objective structured clinical examination in paediatrics.

The assessment of clinical competence has traditionally been carried out through standard evaluations such as multiple choice question and bedside oral examinations. The attributes which constitute clinical competence are multidimensional, and we have modified the objective structured clinical examination (OSCE) to measure these various competencies. We have evaluated the validity and reliability of the OSCE in a paediatric clinical clerkship. We divided the examination into the four components of competence (clinical skills, problem-solving, knowledge, and patient management) and evaluated the performance of 77 fourth-year medical students. The skill and content domains of the OSCE were carefully defined, agreed upon, sampled and reproduced. This qualitative evaluation of the examination was both adequate and appropriate. We achieved both acceptable interstation and intertask reliability. When correlated with concurrent methods of evaluation we found the OSCE to be an accurate measure of paediatric knowledge and patient management skills. The OSCE did not correlate, however, with traditional measures of clinical skills including history-taking and physical examination. Our OSCE, as outlined, offers an objective means of identifying weaknesses and strengths in specific areas of clinical competence and is therefore an important addition to the traditional tools of evaluation.

Clinical Clerkship↗

PubMed1997

Asymmetric Synthesis of Sesaminone: Confirmation of Its Structure and Determination of Its Absolute Configuration.

An asymmetric synthesis of the naturally occurring antipode of the tetrahydrofuran lignan sesaminone ((-)-1) has been achieved. An X-ray crystal structure of the synthetic material validated the structure proposed in the literature for this lignan. Additionally, the absolute configuration of the natural product was established by correlation of the synthetic tetrahydrofuran with the known absolute configuration of L-Phe. The opening of the synthesis was a diastereoselective Evans aldol reaction between N-4-pentenoyloxazolidinone 6 and piperonal. Reduction of the major diastereomer of the aldol product provided enantiomerically pure diol 4. The primary and secondary hydroxyl groups of 4 were protected in tandem to generate silyl ether-MOM ether 9. The vinyl group contained in 9 was then elaborated, via a series of four steps, to aryl ketone 10. This aryl ketone was transformed to a mixture of silyl enol ether stereoisomers (11a,b); TiCl(4)-mediated activation of the MOM ethers contained in this mixture of enol ethers yielded tetrahydrofuran 12 as the major product. Treatment of 12 with fluoride provided synthetic (-)-1.

Journal Article↗

PubMed1991

The solution structures of Escherichia coli trp repressor and trp aporepressor at an intermediate resolution.

We have determined the solution structures and examined the dynamics of the Escherichia coli trp repressor (a 25-kDa dimer), with and without the co-repressor L-tryptophan, from NMR data. This is the largest protein structure thus far determined by NMR. To obtain a set of data sufficient for a structure determination it was essential to resort to isotopic spectral editing. Line broadening observed in this molecular mass range precludes for the most part the measurement of coupling constants and stereospecific assignments, with the inevitable result that the attainable resolution of the final structure will be somewhat lower than the resolution reported for smaller proteins and peptides. Nevertheless the general topology of the protein can be deduced from the subsets of NOEs defining the secondary and tertiary structure, providing a basis for further refinement using the full set of NOEs and energy minimization. We report here (a) an intermediate resolution structure that can be deduced from NMR data, covalent, angular and van-der-Waals constraints only, without resort to detailed energy calculations, and (b) the limits of uncertainty within which this structure is valid. An examination of these structures combined with backbone amide exchange data shows that even at this resolution three important conclusions can be drawn: (a) the protein structure changes upon binding tryptophan; (b) the putative DNA binding region is much more flexible than the core of the molecule, with backbone amide proton exchange rates 1000 times faster than in the core; (c) the binding of tryptophan stabilizes the repressor molecule, which is reflected in both the appearance of additional NOEs, and in the slowing of backbone proton exchange rates by factors of 3-10. Sequence-specific 1H-NMR assignments and the secondary structure of the holopressor (L-tryptophan-bound form) have been reported previously [C. H. Arrowsmith, R. Pachter, R. B. Altman, S. B. Iyer & O. Jardetzky (1990) Biochemistry 29, 6332-6341]. Those for the trp aporepressor (L-tryptophan-free form), made using the same methods and conditions as described in the cited paper, are reported here. The secondary structure of the aporepressor was calculated from sequential and medium-range NOEs and is the same as reported for the holorepressor except that helix E is shorter. The tertiary solution structures for both forms of the repressor were calculated from long-range NOE data.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗

PubMed1998

Verbal aggressiveness: conceptualization and measurement a decade later.

Verbally aggressive messages attack an individual's self-concept to inflict psychological pain. Infante and Wigley developed a trait measure of Verbal aggressiveness; however, the psychometric qualities and validity of the Verbal Aggressiveness scale were not fully explored. In Study I, 119 targets (Mage = 46.2, SDage = 14.1) and 238 observers (Mage = 42.9, SD age = 14.4) participated. In Study II, 112 targets (Mage = 39.9, SDage = 12.9) and 236 observers (Mage = 37.7 SDage = 11.1) participated. In Study III, 153 college students participated (Mage = 25.9, SDage = 4.6). In these studies, temporal stability over two months, criterion-related validity (target-observer agreement), discriminant validity (employing structural equation models), and construct validity (correlations with the facet and domain scales of the NEO-Personality Inventory-R) were investigated. The results justify considering Verbal Aggressiveness as a personality trait and the Verbal Aggressiveness scale as a valid measure.

Adult↗

PubMed1992

Obsessions and compulsions: dimensional structure, reliability, convergent and divergent validity of the Padua Inventory.

This study presents data on dimensional structure, reliability, convergent and divergent validity of the Padua Inventory (PI). In a sample (n = 430) of normal Dutch subjects. The dimensional structure and the strength of the factors were comparable to those found in the Italian sample. The reliability of the PI was found to be satisfactory. As hypothesized substantial correlations were found between the PI and related scales of the Maudsley Obsessive-Compulsive Inventory (MOCI) and between the PI and the subscales Sensitivity, Hostility and Depression of the revised version of the Symptom Checklist. Low correlations were found between the PI on the one side and the Eysenck Personality Questionnaire revised Extraversion, Psychoticism and Social Desirability scale on the other side. Finally, the mean score of the PI differs across the Italian, American and Dutch samples. This is of theoretical interest and deserves further study.

Adolescent↗

PubMed2002

The Dutch Childhood Anxiety Sensitivity Index: psychometric properties and factor structure.

Examined the reliability, validity, and factor structure of the Childhood Anxiety Sensitivity Index (CASI; Silverman, Fleisig, Rabian, & Peterson, 1991) in a Dutch sample. Five hundred forty-four Dutch schoolchildren between 8 and 16 years of age completed Dutch translations of the CASI; the State-Trait Anxiety Inventory for Children (Spielberger, Edwards, Lushene, Montuori, & Platzek, 1973); and the Fear Survey Schedule for Children-Revised (Ollendick, 1983). The Dutch CASI was found to have adequate internal consistency for use with children as well as adolescents. Results reveal that the CASI predicted fear beyond a measure of trait anxiety in this Dutch sample. Both exploratory and confirmatory factor analyses comparing different models were undertaken. The model with 3 first-order factors found in previous studies showed an acceptable fit in this cross-validation sample. Loadings on the 3 factors (Physical Concerns, Mental Concerns, and Publicly Observable Concerns) did not differ between children and adolescents. Results are compared with previous research on the CASI. Directions for future research are discussed.

Adolescent↗

PubMedDate not supplied

Age differences in personality structure revisited: Studies in validity, stability, and change.

Construct validity and longitudinal stability evidence for three cluster dimensions of personality identified as Anxiety, Extraversion, and Openness is examined in a sample of adult males. Correlations with Allport-Vernon-Lindsay Value scales, Cornell Medical Index scores, Eysenck E and N scales, and factors from the SVIB are presented in support of the interpretation of the three clusters. Nine-year longitudinal evidence of stability is presented for Anxiety and Extraversion scores. Previous evidence for change in the structure of Openness to Experience is reconsidered in the light of eleven-year longitudinal data. While the earlier structural differences were not longitudinally replicated, a pattern of external correlates provided evidence for validity of an Openness dimension. Finally, the structural approach to personality development is illustrated by examining the differing relations between field-dependence and tendermindedness in younger and older men.

Adult↗

PubMed1998

Revision and restandardization of the Conners Teacher Rating Scale (CTRS-R): factor structure, reliability, and criterion validity.

The Conners Teacher Rating Scale (CTRS) is a commonly used research and clinical tool for assessing children's behavior in the classroom. The present study introduces the revised CTRS (CTRS-R) which improves on the original CTRS by (1) establishing normative data from a large, representative North American sample, (2) deriving a factor structure using advanced statistical techniques, and (3) updating the item content to reflect current conceptualizations of childhood disorders. Using confirmatory factor analysis, a six-factor structure was found which includes Hyperactivity-Impulsivity, Perfectionism, Inattention/Cognitive Problems, Social Problems, Oppositionality, and Anxious/Shy factors. The reliability of the scale, as measured by test-retest correlations and internal consistency, is generally satisfactory. Using all of the scale factors to discriminate between attention deficit hyperactivity disordered and normal children, 85 percent of children were correctly classified, supporting the validity of the scale and indicating excellent clinical utility. Similarities and differences between the original CTRS factor structure and the CTRS-R factor structure are discussed.

Attention Deficit Disorder with Hyperactivity↗

PubMed1999

Crystal structure of a 14 bp RNA duplex with non-symmetrical tandem GxU wobble base pairs.

Adjacent GxU wobble base pairs are frequently found in rRNA. Atomic structures of small RNA motifs help to provide a better understanding of the effects of various tandem mismatches on duplex structure and stability, thereby providing better rules for RNA structure prediction and validation. The crystal structure of an RNA duplex containing the sequence r(GGUAUUGC-GGUACC)2 has been solved at 2.1 A resolution using experimental phases. Novel refinement strategies were needed for building the correct solvent model. At present, this is the only short RNA duplex structure containing 5'-U-U-3'/3'-G-G-5' non-symmetric tandem GxU wobble base pairs. In the 14mer duplex, the six central base pairs are all displaced away from the helix axis, yielding significant changes in local backbone conformation, helix parameters and charge distribution that may provide specific recognition sites for biologically relevant ligand binding. The greatest deviations from A-form helix occur where the guanine of a wobble base pair stacks over a purine from the opposite strand. In this vicinity, the intra-strand phosphate distances increase significantly, and the major groove width increases up to 3 A. Structural comparisons with other short duplexes containing symmetrical tandem GxU or GxT wobble base pairs show that nearest-neighbor sequence dependencies govern helical twist and the occurrence of cross-strand purine stacks.

Base Pairing↗

PubMed2002

Validating the measurement and structure of self-concept: snapshots of past, present, and future research.

Although the study of self-concept has been a topic of great interest and much study in the social sciences for many decades, it is really only in the past 30 years that any fruitful expansion in knowledge of both its theoretical structure and its related measurement has been forthcoming. From three perspectives--past, present, and future--the author presents abbreviated and selected highlights of important construct validity findings related to this research and postulates possible trends and areas of self-concept research yet to be explored.

Awards and Prizes↗

PubMed1994

[Validity of the Brief Psychiatric Rating Scale].

The internal structure and validity of terms used in the Brief Psychiatric Rating Scale (Overall and Gorham, 1962) was analyzed. The data which had been gained at the entrance examination of 1557 inpatients with the diagnosis according to ICD-9 (schizophrenia simplex, schizophrenia paranoids, schizoaffective disease depressive type, schizoaffective disease manic type, manic-depressive disease manic phase, manic-depressive disease depressive phase) were processed using stepwise discriminant analysis (SDA). Three-dimensional space defined by SDA provided a sufficient frame of relations for the majority of diagnostic groups. Incomplete component analysis justified the assumption of a relatively stabile internal structure of the method. The findings allow to recommend the Czech version of the scale for the purpose of description of psychic impairments in psychiatry.

Adolescent↗

PubMed1994

The Children's Headache Assessment Scale (CHAS): factor structure and psychometric properties.

This study investigated the content validity, factor structure, and psychometric properties of the Children's Headache Assessment Scale (CHAS), a parent rating scale for identifying environmental variables associated with pediatric headache. In Study 1, input from physicians and psychologists was obtained to develop a revised set of 44 items receiving high endorsement. In Study 2, the questionnaire was administered to parents of 92 child headache sufferers, ages 6-16, and readministered 2 weeks later. An exploratory factor analysis revealed five factors (Disruptive Impact, Social Consequences, Stress Antecedents, Physical Antecedents and Quiet Coping, and Prescription Medication Use) that reflect distinct environmental concomitants of childhood headache. Scale reliabilities (alpha, .64-.82) indicate acceptable internal consistency, and test-retest reliabilities indicate relatively stable factors and items. High scores on the Disruptive Impact factor were associated with more severe, lengthy, and infrequent headache occurrence, lending initial support for the validity of this factor. Overall, the findings support the clinical and research utility of the CHAS in behavioral treatment of childhood headache.

Adolescent↗

PubMed1984

A simplistic approach to structural dysplasia assessment: description and validation.

The purpose of this study was to formulate a simplistic method of assessing human structural dysplasia and to validate a classification system that would objectively categorize the type and extent of such dysplasia through the use of indices. Anthropometric measurements were taken from a sample of 222 male college students, length/breadth ratios were formulated, and upper/lower body classifications were made in terms of type and subtype dysplasia. Correlation validation results were highly significant. Body composition data information was also provided for descriptive purposes.

Adipose Tissue↗