The effects of frozen storage at -18 ℃ up to 6 months, on the antioxidant properties, chemical composition and other physicochemical properties of myrtle berries （Myrtus comrnunis L.） has been evaluated. Berries sh...The effects of frozen storage at -18 ℃ up to 6 months, on the antioxidant properties, chemical composition and other physicochemical properties of myrtle berries （Myrtus comrnunis L.） has been evaluated. Berries showed a good resistance to storage decay, and weight loss remained after six months in the 15% range. Results showed that frozen storage up to 6 months affect individual antocyanins content in different ways. Nevertheless the total anthocyanins content was at the end of storage higher than in fresh fruits. The antioxidant capacity calculated with 2,2-diphenyl-l-picrylhidrazyl （DPPH） and 2,2＇-Azino-bis （3-ethylbenzothiazoline-6-sulfonic acid） （ABTS） increased during storage and the calculated r2 showed a positive correlation with the total anthocyanins content. Gluconic and fumaric acid did not changed, quinic acid decreased while malic and shikimic acid increased. The total organic acid content during storage was higher than in fresh fruits causing a slight decrease in pH. Fructose and glucose increased with the same rate and the ratio fructose/glucose remained unchanged （1.06 ± 0.01）, CIE L^＊a^＊b^＊ coordinates showed a shift of the colour to tawny brown after six months storage.展开更多
Antifreeze proteins(AFPs)inhibit ice recrystallization by a mechanism remaining largely elusive.Dynamics of AFPs’hydration water and its involvement in the antifreeze activity have not been identified conclusively.We...Antifreeze proteins(AFPs)inhibit ice recrystallization by a mechanism remaining largely elusive.Dynamics of AFPs’hydration water and its involvement in the antifreeze activity have not been identified conclusively.We herein,by simulation and theory,examined the water reorientation dynamics in the first hydration layer of an AFP from the spruce budworm,Choristoneura fumiferana,compared with a protein cytochrome P450(CYP).The increase of potential acceptor water molecules around donor water molecules leads to the acceleration of hydrogen bond exchange between water molecules.Therefore,the jump reorientation of water molecules around the AFP active region is accelerated.Due to the mutual coupling and excitation of hydrogen bond exchange,with the acceleration of hydrogen bond exchange,the rearrangement of the hydrogen bond network and the frame reorientation of water are accelerated.Therefore,the water reorientation dynamics of AFP is faster than that of CYP.The results of this study provide a new physical image of antifreeze protein and a new understanding of the antifreeze mechanism of antifreeze proteins.展开更多
Antifreeze glycoproteins(AFGPs)facilitate the survival of various organisms in the polar region by preventing internal ice accumulation via an adsorption-inhibition mechanism.Inhibition of AFGP antifreeze activity by ...Antifreeze glycoproteins(AFGPs)facilitate the survival of various organisms in the polar region by preventing internal ice accumulation via an adsorption-inhibition mechanism.Inhibition of AFGP antifreeze activity by the borate buffers has been widely acknowledged as the direct experimental evidence supporting the hydroxyl,rather than methyl,binding mechanism.On the other hand,perturbation of borate binding on the AFGP configuration,which might have considerable influence on the binding efficiency of not only the hydroxyl but also the methyl groups,has rarely been quantitatively examined.Herein we studied,using molecular dynamics simulations,the perturbation on the configuration of a solvated AFGP8 protein induced by the binding of one single borate anion.Near the freezing point,this binding not only makes the disaccharide groups adjacent to the borate-binding disaccharide close to each other but also affects the entire AFGP8 conformation.The structural changes induced by the binding of borate on different disaccharide sidechains exhibit clear site-specificities and the effect of borate binding on the structural changes is significantly reduced at higher temperatures.Our study is valuable for further understanding the relationship between the structure and antifreeze activity of these antifreeze glycoproteins.展开更多
文摘The effects of frozen storage at -18 ℃ up to 6 months, on the antioxidant properties, chemical composition and other physicochemical properties of myrtle berries （Myrtus comrnunis L.） has been evaluated. Berries showed a good resistance to storage decay, and weight loss remained after six months in the 15% range. Results showed that frozen storage up to 6 months affect individual antocyanins content in different ways. Nevertheless the total anthocyanins content was at the end of storage higher than in fresh fruits. The antioxidant capacity calculated with 2,2-diphenyl-l-picrylhidrazyl （DPPH） and 2,2＇-Azino-bis （3-ethylbenzothiazoline-6-sulfonic acid） （ABTS） increased during storage and the calculated r2 showed a positive correlation with the total anthocyanins content. Gluconic and fumaric acid did not changed, quinic acid decreased while malic and shikimic acid increased. The total organic acid content during storage was higher than in fresh fruits causing a slight decrease in pH. Fructose and glucose increased with the same rate and the ratio fructose/glucose remained unchanged （1.06 ± 0.01）, CIE L^＊a^＊b^＊ coordinates showed a shift of the colour to tawny brown after six months storage.
基金supported by the National Natural Science Foundation of China(No.21873101 and No.22063007)the support of the Natural Science Foundation of Inner Mongolia(No.2020MS02018)Scientific Research Foundation of IMUN for doctors(BS581)。
文摘Antifreeze proteins(AFPs)inhibit ice recrystallization by a mechanism remaining largely elusive.Dynamics of AFPs’hydration water and its involvement in the antifreeze activity have not been identified conclusively.We herein,by simulation and theory,examined the water reorientation dynamics in the first hydration layer of an AFP from the spruce budworm,Choristoneura fumiferana,compared with a protein cytochrome P450(CYP).The increase of potential acceptor water molecules around donor water molecules leads to the acceleration of hydrogen bond exchange between water molecules.Therefore,the jump reorientation of water molecules around the AFP active region is accelerated.Due to the mutual coupling and excitation of hydrogen bond exchange,with the acceleration of hydrogen bond exchange,the rearrangement of the hydrogen bond network and the frame reorientation of water are accelerated.Therefore,the water reorientation dynamics of AFP is faster than that of CYP.The results of this study provide a new physical image of antifreeze protein and a new understanding of the antifreeze mechanism of antifreeze proteins.
基金support from the National Natural Science Foundation of China(No.21873101)is acknowledged。
文摘Antifreeze glycoproteins(AFGPs)facilitate the survival of various organisms in the polar region by preventing internal ice accumulation via an adsorption-inhibition mechanism.Inhibition of AFGP antifreeze activity by the borate buffers has been widely acknowledged as the direct experimental evidence supporting the hydroxyl,rather than methyl,binding mechanism.On the other hand,perturbation of borate binding on the AFGP configuration,which might have considerable influence on the binding efficiency of not only the hydroxyl but also the methyl groups,has rarely been quantitatively examined.Herein we studied,using molecular dynamics simulations,the perturbation on the configuration of a solvated AFGP8 protein induced by the binding of one single borate anion.Near the freezing point,this binding not only makes the disaccharide groups adjacent to the borate-binding disaccharide close to each other but also affects the entire AFGP8 conformation.The structural changes induced by the binding of borate on different disaccharide sidechains exhibit clear site-specificities and the effect of borate binding on the structural changes is significantly reduced at higher temperatures.Our study is valuable for further understanding the relationship between the structure and antifreeze activity of these antifreeze glycoproteins.
