PubMed · 9170916
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
S Hirono, H Gouda, K Ebisawa. 1997. [Computer simulations using molecular dynamics methods].. https://pubmed.ncbi.nlm.nih.gov/9170916/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Amino acid (AA) profiles from body fluids such as blood and urine are clinical indicators for diagnosing metabolic and hepatic diseases. Current quantitative methods, such as liquid chromatography-mass spectrometry (LC-MS) with isotopically labelled internal standards (ISs), are costly and technically demanding. This study proposes a cost-efficient alternative using structural isomers as ISs in a direct liquid infusion (DLI) tandem mass spectrometry (MS/MS) approach. The method leverages chimeric spectra and fragment intensity ratios to quantify AAs, demonstrating high linearity and precision even with a 3D ion trap mass analyser. This approach offers a viable strategy for AA quantification in preventive medicine, particularly for screening metabolic diseases such as phenylketonuria, diabetes, and liver dysfunction.
We have purified and characterized a collagenase/gelatinase activity expressed during sea urchin embryonic development. The native molecular mass was determined to be 160 kDa, while gelatin substrate gel zymography revealed an active species of 41 kDa, suggesting that the native enzyme is a tetramer of active subunits. Incubation in the presence of EGTA resulted in nearly complete loss of activity and this effect could be reversed by calcium. Calcium-induced reactivation appeared to be cooperative and occurred with an apparent kd value of 3.7 mM. Two modes of calcium binding to the 41-kDa subunit were detected; up to 80 moles of calcium bound with a kd value of 0.5 mM, while an additional 120 moles bound with a kd value of 5 mM. Amino acid analysis revealed a carboxy plus carboxyamide content of 24.3 mol/100 mol, indicating the availability of substantial numbers of weak Ca2+-binding sites. Calcium binding did not result in either secondary or quaternary structural changes in the collagenase/gelatinase, suggesting that Ca2+ may facilitate activation through directly mediating the binding of substrate to the enzyme. The collagenase/gelatinase activity was detected in blastocoelic fluid and in the hyalin fraction dissociated from 1-h-old embryos. Immunolocalization studies revealed two storage compartments in the egg; cortical granules and small granules/vesicles dispersed throughout the cytoplasm. After fertilization, the antigen was detected in both the apical and basal extracellular matrices, the hyaline layer, and basal lamina, respectively.
The function of articular cartilage as a weight-bearing tissue depends on the specific arrangement of collagen types II and IX into a three-dimensional organized collagen network that can balance the swelling pressure of the proteoglycan/water gel. To determine whether cartilage engineered in vitro contains a functional collagen network, chondrocyte-polymer constructs were cultured for up to 6 weeks and analyzed with respect to the composition and ultrastructure of collagen by using biochemical and immunochemical methods and scanning electron microscopy. Total collagen content and the concentration of pyridinium crosslinks were significantly (57% and 70%, respectively) lower in tissue-engineered cartilage that in bovine calf articular cartilage. However, the fractions of collagen types II, IX, and X and the collagen network organization, density, and fibril diameter in engineered cartilage were not significantly different from those in natural articular cartilage. The implications of these findings for the field of tissue engineering are that differentiated chondrocytes are capable of forming a complex structure of collagen matrix in vitro, producing a tissue similar to natural articular cartilage on an ultrastructural scale.