Thermal Stability Of Type Research Articles

Thermal Stability of Type II Modifications Inscribed by Femtosecond Laser in a Fiber Drawn from a 3D Printed Preform

Fiber drawing from a 3D printed perform was recently discussed to go beyond the limitations of conventional optical fiber manufacturing in terms of structure and materials. In this work, the photosensitivity of silica optical fibers to femtosecond laser light, and fabricated by 3D printing a preform, is investigated. The writing kinetics and the thermal performance of Type II modifications are studied by varying the laser pulse energy and investigating the birefringence response of the femtosecond (fs)-laser written structures. Compared with a conventional telecom single mode fiber (SMF28), the fiber made by 3D printing is found to have similar writing kinetics and thermal performance. Additionally, the thermal stability of the imprinted fs-laser induced nanostructures is investigated based on the Rayleigh–Plesset equation, describing a model of nanopores dissolution underpinning Type II modifications with thermal annealing.

Influence of palygorskite on the structure and thermal stability of collagen

We investigated the influence of palygorskite on the conformation and thermal stability of type I collagen. Fluorescence spectroscopy and Fourier transform infrared spectroscopy (FTIR) studies demonstrated that the interaction between collagen and purified palygorskite (PAL) led to the contraction and aggregation of collagen molecules, but did not destroy the triple helix backbone of collagen. Due to the structure of collagen and PAL, the interaction mainly involved hydrogen bonding and electrostatic forces. Atomic force microscopy (AFM) observations clearly displayed the nanorod morphology of PAL, and further revealed the fibril aggregation of collagen in the presence of PAL. Differential scanning calorimetry (DSC) measurements indicated that the PAL-collagen nanocomposites improved the thermal stability in comparison with pure collagen. The present study showed that PAL could modify collagen as a reinforcing agent and preserve the triple helix structure of collagen.

Thermal stabilization of Type I fiber Bragg gratings for operation up to 600°C

The thermal stability of Type I gratings is increased by postthermal tuning of the grating. Optimization of the procedure leads to gratings that can withstand temperatures as high as 600 degrees C. Aging tests lead to lifetime predictions as high as 25 years with <3 dB reduction at 400 degrees C. Single exponential relaxation is observed. Above 800 degrees C regeneration is obtained.

The Rough Endoplasmic Reticulum-resident FK506-binding Protein FKBP65 Is a Molecular Chaperone That Interacts with Collagens

The rough endoplasmic reticulum-resident FK-506-binding protein FKBP65 can be isolated from chick embryos on a gelatin-Sepharose column, indicating some involvement in the biosynthesis of procollagens. The peptidylprolyl cis-trans-isomerase activity of FKBP65 was previously shown to have only marginal effects on the rate of triple helix formation (Zeng, B., MacDonald, J. R., Bann, J. G., Beck, K., Gambee, J. E., Boswell, B. A., and Bächinger, H. P. (1998) Biochem. J. 330, 109-114). Here we show that FKBP65 is a monomer in solution and acts as a chaperone molecule when tested with two classic chaperone assays: FKBP65 inhibits the thermal aggregation of citrate synthase and is active in the denatured rhodanese refolding and aggregation assay. The chaperone activity is comparable to that of protein-disulfide isomerase, a well characterized chaperone. FKBP65 delays the in vitro fibril formation of type I collagen, indicating that FKBP65 is also able to interact with triple helical collagen, and acts as a collagen chaperone.

Changes in Thermal Stability and Microunfolding Pattern of Collagen Helix Resulting from the Loss of α2(I) Chain in Osteogenesis Imperfecta Murine

Homozygous mutations resulting in formation of α1(I) 3 homotrimers instead of normal type I collagen cause mild to severe osteogenesis imperfecta (OI) in humans and mice. Limited studies of changes in thermal stability of type I homotrimers were reported previously, but the results were not fully consistent. We revisited this question in more detail using purified tendon collagen from wild-type (α1(I) 2α2(I) heterotrimers) and oim (α1(I) 3) mice as well as artificial α1(I) 3 homotrimers obtained by refolding of rat-tail-tendon collagen. We found that at the same heating rate oim homotrimers completely denature at ∼2.5 deg.C higher temperature than wild-type heterotrimers, as determined by differential scanning calorimetry. At the same, constant temperature, homotrimers denature ∼100 times slower than heterotrimers, as determined by circular dichroism. Detailed analysis of proteolytic cleavage at different temperatures revealed that microunfolding of oim homotrimers and wild-type heterotrimers occurs at similar rate but within a number of different sites. In particular, the weakest spot on the oim triple helix is located ∼100 amino acid residues from the C-terminal end within the cyanogen bromide peptide CB6. The same microunfolding site is also present in wild-type collagen, but the weakest spot of the latter is located close to the N-terminal end of CB8. Amino acid analysis and differential gel electrophoresis showed virtually no posttranslational overmodification of oim mouse tendon collagen. Moreover, thermal stability and microunfolding of artificial rat-tail-tendon homotrimers were similar to oim homotrimers. Thus, the observed changes are associated with difference in the amino acid composition of α1(I) and α2(I) chains rather than posttranslational overmodification.

Effects of animal and muscle characteristics on collagen and consequences for ham production

The effect of biological and technological factors on ham production were studied by analyzing collagen pyridinoline cross-linking and the thermal stability of type I collagen. The type of muscle affected hydroxylysylpyridinoline ( P>0.01) and lysylpyridinoline ( P<0.001) cross-linking, total intramuscular collagen concentration ( P<0.0001), and the slope of type I collagen solubility as a function of time. pH ( P<0.05) and genetic line ( P<0.0001) affected lysylpyridinoline cross-linking. In ham production, muscle type, pH 24, nitrite salt concentration and pasteurization value affected type I collagen solubility ( P<0.0001). There was a relationship between pyridinoline cross-linking and soluble type I collagen levels and between technological yield and soluble type I collagen concentration ( P<0.0001). There was also a relationship between collagen pyridinoline cross-linking and technological yield if the nitrite salt (1.5%) and pH 24 (<5.55) were kept constant. Thus collagen solubility and pyridinoline content are two indicators of meat quality in ham production.

Type X collagen biosynthesis and expression in avian tibial dyschondroplasia

Objective: Tibial dyschondroplasia (TD) is an abnormality of growth plate cartilage characterized by the presence of non-vascularized, non-mineralized tissue. The objective of this study was to examine structural and functional alterations of the growth plate-specific type X collagen in RTD cartilage.Design: Collagen biosynthesis was examined in organ cultures and in cultured chondrocytes from normal growth plate and TD cartilage. Thermal stability of type X collagen extracted from normal and TD cartilage organ cultures to protease digestions by trypsin plus chymotrypsin bacterial collagenase was determined. The expression of collagen genes was examined in cultured normal and TD chondrocytes.Results: Synthesis of total collagen and of type X collagen was greater than threefold higher in organ cultures from the TD lesion compared with normal growth plate. The increase in type X collagen synthesis in the lesion was compensated by a reduction in the relative proportions of types II and XI collagens. The thermal denaturation and collagenase cleavage properties of purified types II and X collagens from TD cartilage were normal. The expression of type X collagen gene was threefold higher in cultured TD chondrocytes compared to chondrocytes from normal growth plate. Normal growth plate chondrocytes in primary cultures synthesized predominantly type X collagen (80% of total collagen). In contrast, TD chondrocytes synthesized mainly types I and II collagens and type X collagen represented only 22% of total collagen. TD cells initiated the synthesis of type I collagen within 5 days of primary culture, whereas normal chondrocytes did not synthesize this collagen during the same culture period. Although type X collagen synthesis was reduced in TD chondrocytes, the mRNA levels for type X collagen were substantially higher than in normal chondrocytes.Conclusion: Accumulation of type X collagen in TD cartilage results from its increased biosynthesis which is due largely to increased expression of the gene for this collagen, although, the chondrocyte culture studies suggest the possibility of postranscriptional defect in type X collagen synthesis or processing in TD lesion. Moreover, the TD chondrocytes in contrast with normal chondrocytes display evidence of prompt loss of their specific phenotype during short-term primary cultures.

Thermal stability of type I and type III procollagens from normal human fibroblasts and from a patient with osteogenesis imperfecta.

Type I and type III procollagens were isolated from the medium of human fibroblast cultures in amounts adequate for examination by circular dichroism. Type I procollagen had a spectrum similar to that of type I procollagen and collagen from chicken embryos. The human type III procollagen showed a red shift not seen in type III collagen from calf skin. The midpoint (tm) for the helix-to-coil transition for both human procollagens was 40 degrees C. the same tm values were obtained with type I and type III procollagens synthesized by fibroblasts from a patient with osteogenesis imperfecta. Type I procollagen synthesized by the patient's fibroblasts, however, tended to aggregate more readily than type I procollagen from normal human fibroblasts, apparently because of a structural alteration of the protein.