Sionkowska Alina
Faculty of Chemistry, Nicolaus Copernicus University, 7 Gagarin, 87-100 Torun, Poland.
J Photochem Photobiol B. 2005 Aug 1;80(2):87-92. doi: 10.1016/j.jphotobiol.2005.03.007. Epub 2005 Apr 26.
The thermal stability of UVB irradiated collagen in bovine lens capsules and in bovine cornea has been investigated by differential scanning calorimetry (DSC). During UVB irradiation the lens capsules and cornea were immersed in water to keep the collagen in a fully hydrated condition at all times. UV irradiation induced changes in collagen which caused both stabilization and destabilization of the collagen structure. The helix-coil transition for non-irradiated collagen in cornea occurred near 66 degrees C, instead for the irradiated one for 3h it occurred at 69 degrees C. After irradiating for longer times (20-96h) the helix-coil transition peak occurred at much lower temperatures. The peak was very broad and suggested that collagen was reduced by UV to different polypeptides of different molecular weight and different lower thermal stabilities. The irradiation of lens capsules with UVB light in vitro resulted in changes in the thermal properties of type-IV collagen consistent with increased cross-linking. DSC of lens capsules showed two major peaks at melting temperatures at 54 degrees C Tm1 and 78 degrees C Tm2, which can be attributed to the denaturation of the triple helix and 7S domains, respectively. UVB irradiation of lens capsules in vitro for 6 h caused an increase in Tm1 from 54 to 57 degrees C. The higher temperature required to denature the type-IV collagen after irradiation in vitro suggested an increase of intermolecular cross-linking.
通过差示扫描量热法（DSC）研究了紫外线B（UVB）照射牛晶状体囊膜和牛角膜中胶原蛋白的热稳定性。在UVB照射过程中，将晶状体囊膜和角膜浸入水中，以使胶原蛋白始终保持完全水合状态。紫外线照射引起胶原蛋白的变化，导致胶原蛋白结构的稳定和不稳定。未照射的角膜胶原蛋白的螺旋-卷曲转变发生在66摄氏度左右，而照射3小时的胶原蛋白的螺旋-卷曲转变发生在69摄氏度。照射更长时间（20-96小时）后，螺旋-卷曲转变峰出现在低得多的温度下。该峰非常宽，表明紫外线将胶原蛋白降解为不同分子量和不同较低热稳定性的不同多肽。体外UVB照射晶状体囊膜导致IV型胶原蛋白的热性质发生变化，这与交联增加一致。晶状体囊膜的DSC在54摄氏度（Tm1）和78摄氏度（Tm2）的熔化温度处显示两个主要峰，这分别可归因于三螺旋和7S结构域的变性。体外UVB照射晶状体囊膜6小时导致Tm1从54摄氏度增加到57摄氏度。体外照射后使IV型胶原蛋白变性所需的较高温度表明分子间交联增加。
