Protective Effect of Vitamin C on Protien Activity in Plasma
during Virus Inactivation
Abstract To determine whether addition of vitamin C (Vit C) to single-unit plasma could influence the efficacy of inactivating viruses and could maintain the activity of plasma proteins by methylene blue (MB)-light treatment.Vesicular stomatitis virus (VSV) Indiana strain was used as the indicating virus.Human plasma containing VSV was added with different concentrations of Vit C and final concentration 1 μmol/L MB and irradiated by fluorescence at an intensity of 40 000 lx,samples were collected at different times for detection.Cytopathic effect was used to test the effect of virus inactivation.A segment of the nucleic acid encoding capsid protein of VSV was amplified with RT-PCR.Some methods,such as the Clauss method,the one-stage method,microimmunoelectrophoresis,were used to investigate the changes of plasma components.The results showed that when the VSV plasma was added with 240 μmol/L Vit C and treated by MB-light irradiation for 60 min,the titer of VSV decreased by more than 8 lg TICD50/ml.Meanwhile,target segment amplification of VSV was also negative.The recovery rates of fibrinogen and coagulation factor Ⅷ (FⅧ:C ) were 83.55% and 81.67% respectively,which had significant difference comparing with the routine MB-fluorescent light treatment. Most of plasma proteins were not affected significantly.No change in immunogenicity of these proteins was observed by using microimmunoelectrophoresis. It is concluded that virus inactivation is not influenced and plasma proteins are effectively protected by Vit C. Vit C can be used as a protector and is beneficial to improving the quality of plasma subjected to MB-photodynamic treatment.
Key words vitamin C; methylene blue-light treatment; virus inactivation; plasma protein
加入240 μmol/L Vit C與未加Vit C對照組相比較,MB光化學法滅活病毒動力學曲線走勢基本一致,光照15分鐘內病毒滴度急劇下降,到60分鐘時,滴度為0,﹥8 lg TCID50/ml VSV被完全滅活。再將VSV盲傳培養3代,結果都未見細胞病變。但是在含480 μmol/L Vit C的血漿中,病毒滅活的效果顯著下降,處理15分鐘時,病毒滴度下降至4.5 lg TCID50/ml,之后處于1個平臺期,到60分鐘時,滴度仍 > 4 lg TCID50/ml(圖1)。因此,在血漿中加入240 μmol/L Vit C經MB光照60分鐘,能完全滅活VSV病毒。
MB光化學法處理前后血漿的總蛋白、白蛋白、膽固醇、甘油三酯、尿素氮和肌酐等含量稍有減少,天冬氨酸轉氨酶、谷丙轉氨酶等酶活性也有不同程度下降,只有總膽紅素含量顯著降低了80%(表1未顯示全部指標)。從總的趨勢來看,FFP+MB+Vit C組受損傷程度一般都要小于FFP+MB組。從血漿的凝血因子活性檢測結果來看,FFP+MB組Fg和FⅧ:C的回收率分別為68.49%﹑71.07%,而FFP+MB+Vit C組達到83.55%﹑81.67%,用方差分析的方法統計二者差異有統計學意義。Table 1.Results of biochemical and biological tests of plasma (略)
Vit C作為自由基清除劑,是血漿中最主要的水溶性抗氧化分子,本身是人體每天所必需的。Vit C清除自由基的能力在光照射過程中隨自由基大量產生而得到發揮,故在光照前加入Vit C能更好地清除自由基,保護抗氧化酶的活性,使自由基與抗氧化系統達到一個新的平衡[12] 。本實驗在血漿中加入240 μmol/L Vit C時,不影響MB光化學法滅活病毒的效果,這可能是在此濃度下,Vit C對自由基的淬滅和MB光化學法使自由基的產生達到了較為理想的平衡狀態。而當加入480 μmol/L Vit C,滅活病毒的能力反而下降,這可能是太高劑量的Vit C能還原亞甲基藍,從而減弱光化學效應的強度;也可能是高劑量Vit C清除更多數量的1O2和一些自由基,從而影響了病毒滅活效果。
實驗中,我們也用RT-PCR法擴增VSV編碼核衣殼蛋白404-820位堿基,根據條帶有無及亮度差別,以推斷VSV的RNA含量。結果顯示,照射VSV血漿<45分鐘,RT-PCR能擴增出目的條帶,但是隨著時間延長,擴增產物減少。照射60分鐘時,擴增結果為陰性,完全不能檢出VSV的核衣殼基因。這一結果與細胞病變效應結果一致。這也說明了MB光化學法對VSV的RNA具有損傷作用,這種損傷作用隨著滅活時間的延長而加大。這也進一步提示了,VSV感染性的有無與核衣殼基因片段擴增產物檢出與否存在平行關系。通過CPE法、一期法、微量免疫電泳法等證實,加入240 μmol/L Vit C處理組與未加Vit C對照組相比較,MB光化學法滅活病毒的效果基本一致,但是前者對Fg和FⅧ:C的保護作用卻顯著加強,確實起到了保護血漿蛋白的作用。
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Abstract In order to optimize the18O labeling method,two key aspects,peptide dispersion and trypsin deactivation were discussed。The addition of RapigestTM SF in H218O and microwave heating enhanced labeling efficiency of α-casein digested peptides(18O/16O ratio >99%).Chemical modification with tris(2-carboxyethyl)phosphine(TCEP) and iodoacetamide(IAA) resulted in trypsin deactivated completely.No significant back-exchange from 18O to16O was observed after labeling in 6 days.The experiment result with peptide mixture from showed that the improved method could be effectively used to label protein and peptide.
Fig.1 MALDI-TOF-TOF-MS spectrum of tryptic digested peptides of α-casein
A.未標記的α-casein酶切肽段質譜圖(Spectrum of unlabeled peptide mixture);B.m/z 1267,1660和2316的肽段標記前質譜圖(Spectrum of unlabeled peptides with m/z of 1267,1660 and 2316); C.m/z 1267,1660和2316的肽段未加RapigestTM SF,孵育過夜標記后的質譜圖(Spectrum of labeled peptides with m/z of 1267,1660 and 2316 without RapigestTM SF,at 37 ℃ for 24 h); D.m/z 1267,1660和2316的肽段加入RapigestTM SF,孵育過夜標記后的質譜圖(Spectrum of labeled peptides with m/z of 1267,1660 and 2316 with RapigestTM SF,at 37 ℃ for 24 h); E.質荷比為1267,1660和2316的肽段加入RapigestTM SF,微波加熱10 min標記的質譜圖(Spectrum of labeled peptides with m/z of 1267,1660 and 2316 with RapigestTM SF and Microwave heating for 10 min)。
Fig.3 Labeling efficiency of thyroglobin peptides with 18O(18O incorporation efficiency was calculated by 18O/16O ratio of the first isotopic peak area)
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