262,243 research outputs found
Moderately severe osteogenesis imperfecta: biochemical studies showing variable defect localization in the triple-helical domain of type I collagen.
No full textThis report describes the biochemical investigations on six patients affected by a moderate form of Osteogenesis Imperfecta (type IV according to the Sillence classification). Biochemical characterization of type I collagen produced by skin fibroblasts showed considerable heterogeneity: in three patients out of six, collagen appeared normal; while in the three others a structural defect in the protein was present. In these probands the mutations were localized in different regions of the triple helix domain (corresponding to peptides alpha 1(I)CB6 and alpha 1(I)CB7). In two probands showing the defect in alpha 1(I)CB7, a decrease of the thermal stability of the protein was present
Possible role of overglycosylation in the type I collagen triple helical domain in the molecular pathogenesis of osteogenesis imperfecta.
No full textThe underlying defect in patients affected by a form of osteogenesis imperfecta (OI) clarified at the molecular level regards the amount or the structure of type I collagen synthesized. This leads to a decreased and/or abnormal mineral deposition in bone and affects bone mass and/or strength. Abnormal interactions between collagen molecules in the presence of mutant trimers could give rise to abnormal fibrils, which, in turn, can determine incorrect interactions with noncollagenous matrix macromolecules. The interactions can be disturbed or modulated by an abnormal distribution on the collagen fibril surface of electrically charged or hydrophobic groups, or by an increased presence of sugar moieties linked to hydroxylysyl residues due to chain post-translational overmodifications (lysyl overhydroxylation and hydroxylysyl overglycosylation) of the portion of the triple helical domain of abnormal type I collagen molecules N-terminal with respect to the defect localization
Coons Patch, Hermite Interpolation, and High-Order Finite Elements in Structural Dynamics
No full textThe paper presents a novel finite element for the evaluation of the natural modes of vibrations of complex structures. The element is based upon a three-dimensional extension of the Coons patch technique, combined with the fact that the generating lines are obtained using the Hermite interpolation technique; the resulting finite-element unknowns are the nodal values of: (i) the unknownfunction (the displacement vector in our case), and (ii) the Cartesian components of its gradient. In addition, the paper presents a review of recent work by the authors on another closely related element, which is an extension to complex configurations of the Hermite element, which in turn is based upon the three-dimensional extension of the Hermite interpolation; in this case, the finite-elementunknowns are the nodal values of: (i) the unknown function, (ii) the Cartesian components of its gradient, (iii) its three second?order mixed derivatives, and (iv) its third-order mixed derivative. The objective of these methods is the user?friendly evaluation of natural modes of vibration of elastic structures, as used in multi-disciplinary optimization; accordingly, in order to validate and assess the two methods, numerical results for simple test cases are included; we concentrate on the natural frequencies of elastic plates (which are treated as three-dimensional structures, with only one elementalong the normal). In addition, in view of the fact that the ultimate objective is the applicability of the techniques for arbitrary geometries, results for a relatively complex structure (that is, a simplifiedmodel of a wing box) are included
Stability of type I collagen peptide trimers.
No full textAs indices of triple helix stability of type I collagen CNBr peptide homotrimers, Delta G degrees for monomer-trimer transitions and melting temperatures were obtained from circular dichroism measurements at increasing temperatures. The data were compared with the stability of the parent native molecule. Peptides were found to have a lower stability than the whole collagen molecule. The general implication is that the coordinated water molecules play a key role in determining collagen triple helical stability and high cooperativity at melting. Other factors (monomer stability, ionic and hydrophobic factors, variations of composition, specific sequence) could also contribute towards peptide stability; these factors could explain the data obtained in the case of peptide alpha 1(I) CB3
A de novo G to T transversion in a pro-alpha 1(I) collagen gene for a moderate case of osteogenesis imperfecta. Substitution of cysteine for glycine 178 in the triple helical domain
No full textCultured fibroblasts from a patient affected with a moderate form of osteogenesis imperfecta were defective for the synthesis of type I collagen molecules; about half of the α1(I) chains contained a cysteine residue in the triple helical domain and a disulfide link formed when two mutant α1(I) chains were incorporated into a type I collagen heterotrimer. The proband's parents were clinically and biochemically normal. The cysteine was localized within peptide α1(I)CB8 between residues 170 and 200 of the triple helical domain using a chemical procedure with 2-nitro-5-thiocyanobenzoic acid (Tenni, R., Rossi, A., Valli, M., Mottes, M., Pignatti, P.F., and Cetta, G. (1990) Matrix 10, 20-26). Type I procollagen heterotrimers containing either one or two mutant chains showed (i) a slight abnormality in secretion from cells, (ii) a low degree of post-translational overmodifications; (iii) the same, but lower than normal, thermal stability. Total RNA was isolated from the proband's dermal fibroblast cultures, and cDNAs for pro-α1(I) were prepared using total RNA. A portion of cDNA, coding for the region encompassing residues 119-193 of α1(I) triple helical domain, was amplified by polymerase chain reaction. A single base pair mismatch was identified by chemical cleavage of DNA·DNA heteroduplexes, indicating a possible substitution of a guanine in the triplet coding for glycine 178 or 181. The same unique mismatch was detected by chemical cleavage in about one-half of the molecules in heteroduplexes formed between patient's pro-α1(I) mRNAs and a normal cDNA probe.The amplified products were cloned and sequenced, confirming the heterozygous nature of the patient and demonstrating the presence and the location of a missense mutation; a single T for G substitution was found in the first base of the triplet coding for residue 178 of α1(I) triple helical domain, leading to a cysteine for glycine substitution. Allele-specific oligonucleotide hybridization to amplified DNA confirmed a de novo point mutation in the proband's genome. The findings in this patient are in accord with the phenotypic gradient model, which correlates the localization of the structural defect with the clinical outcome of osteogenesis imperfecta. The mutant protein has some properties that differ from that caused by the cysteine for glycine 175 substitution, suggesting a direct influence of the neighboring amino acids on the effects of the mutation
A de novo G to T transversion in a pro-a1(I) collagen gene for a moderate case of osteogenesis imperfecta. Substitution of cysteine for glycine 178 in the triple helical domain.
No full textCultured fibroblasts from a patient affected with a moderate form of osteogenesis imperfecta were defective for the synthesis of type I collagen molecules; about half of the alpha 1(I) chains contained a cysteine residue in the triple helical domain and a disulfide link formed when two mutant alpha 1(I) chains were incorporated into a type I collagen heterotrimer. The proband's parents were clinically and biochemically normal. The cysteine was localized within peptide alpha 1(I)CB8 between residues 170 and 200 of the triple helical domain using a chemical procedure with 2-nitro-5-thiocyanobenzoic acid (Tenni, R., Rossi, A., Valli, M., Mottes, M., Pignatti, P. F., and Cetta, G. (1990) Matrix 10, 20-26). Type I procollagen heterotrimers containing either one or two mutant chains showed (i) a slight abnormality in secretion from cells; (ii) a low degree of post-translational overmodifications; (iii) the same, but lower than normal, thermal stability. Total RNA was isolated from the proband's dermal fibroblast cultures, and cDNAs for pro-alpha 1(I) were prepared d using total RNA. A portion of cDNA, coding for the region encompassing residues 119-193 of alpha 1(I) triple helical domain, was amplified by polymerase chain reaction. A single base pair mismatch was identified by chemical cleavage of DNA.DNA heteroduplexes, indicating a possible substitution of a guanine in the triplet coding for glycine 178 or 181. The same unique mismatch was detected by chemical cleavage in about one-half of the molecules in heteroduplexes formed between patient's pro-alpha 1(I) mRNAs and a normal cDNA probe. The amplified products were cloned and sequenced, confirming the heterozygous nature of the patient and demonstrating the presence and the location of a missense mutation; a single T for G substitution was found in the first base of the triplet coding for residue 178 of alpha 1(I) triple helical domain, leading to a cysteine for glycine substitution. Allele-specific oligonucleotide hybridization to amplified DNA confirmed a de novo point mutation in the proband's genome. The findings in this patient are in accord with the phenotypic gradient model, which correlates the localization of the structural defect with the clinical outcome of osteogenesis imperfecta. The mutant protein has some properties that differ from the caused by the cysteine for glycine 175 substitution, suggesting a direct influence of the neighboring amino acids on the effects of the mutation
Anomalous cysteine in type I collagen. Localisation by chemical cleavage of the protein using 2-nitro-5-thiocyanobenzoic acid and by mismatch analysis of cDNA heteroduplexes
No full textA method is presented for the localisation of an anomalous cysteine inside the triple helical domain of type I collagen from a patient affected with Osteogenesis Imperfecta. The chemical cleavage used relies on the specificity and reactivity of the thiol side chain versus 2-nitro-5-thiocyanobenzoic acid, to yield cyanocysteine; in mild alkaline conditions this derivative will undergo the breakdown of its N-side peptide bond. This method could allow a more precise localisation of anomalous cysteine in both type I collagen alpha chains, alpha 1(I) and alpha 2(I), compared to previous analytical methods on CNBr peptides. For the mutant alpha 1(I) chains from a patient affected by Osteogenesis Imperfecta, we found a location of cysteine in the peptide alpha 1(I)CB8, between amino acids 170-200. Biochemical localisation was confirmed by a chemical cleavage method for mismatched cytosines on heteroduplexes obtained after denaturation and annealing of a 233 bp cDNA fragment amplified by PCR from the heterozygote patient
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Communities, Identity and Borders: What does the Kenmure Street Protest tell us about belonging to Glasgow?
No full textThe way we control our borders and treat those who want or need to cross them says so much about our national identity. And for the last 25 years, the U.K. Government has - with significant public support - moved to make immigration as difficult as possible. But in contrast, the Scottish government has been more focused on encouraging migration to Scotland to address population decline and contribute to the Scottish economy.
This episode of Recovering Community begins with the Kenmure Street Protest, when community resistance to a Home Office raid resulted in the release of two men back into their neighbourhood.
Anne Kerr talks to Teresa Piacentini, David Millar, Pinar Aksu and Cetta Mainwaring to consider the ways that community activism in Glasgow sets the city apart from wider UK sentiment towards immigration
Type I collagen CNBr peptides: species and behavior in solution
No full textThe properties of type I collagen CNBr peptides in solution were studied to investigate the molecular species formed, their conformation, and factors influencing equilibria between peptide species. Peptides formed homologous trimers, even though the native parent protein is heterotrimeric, [alpha 1(I)]2 alpha 2-(I). Their triple-helical content was found to be high (> 75% for most peptides). Full helical content was not reached mainly because of the presence of monomer species; chain misalignment, if present, and trimer unraveling at terminal ends appeared to play a minor role in reducing helicity. Circular dichroism spectra and resistance to trypsin digestion at 4 and 20 degrees C demonstrated that the conformation of trimers was very similar to the collagen triple-helical conformation. Rotary shadowing of peptide alpha 1(I) CB7 supported this finding. Analytical gel filtration in nondenaturing conditions showed that the trimers of some peptides have the ability to autoaggregate. In the case of peptides alpha 1(I) CB8 and alpha 2(I) CB4, most of the intermolecular interactions between trimeric molecules were disrupted by 0.5 M NaCl, demonstrating that their ionic character is important. Changes in ionic strength also altered the hydrodynamic size of single- and triple-stranded molecules. The different molecular species are in equilibrium. The kinetics of the conversion of trimer to monomer species was determined in a time course experiment using trypsin digestion and found to be a relatively slow process (trimer half-life is a few days at 4 degrees C, about one order of magnitude lower at 20 degrees C) with an activation energy of roughly 4-9 kcal/mol. The circular dichroism profile at increasing temperatures showed that the melting temperature for triple-helical peptides is about 6-10 degrees C lower than that of the parent native type I collagen. The folding of peptides is a spontaneous process (exothermic but with unfavourable entropy change), and the triple-helical conformation originates solely as the result of the collagen sequence because it forms from heat-denatured samples
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