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双功能尿苷酰转移/去除酶GlnD在谷氨酸棒杆菌JNR中的功能 被引量:2
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作者 李静 徐美娟 +6 位作者 舒群峰 赵雅雯 唐蜜 张显 杨套伟 许正宏 饶志明 《微生物学报》 CAS CSCD 北大核心 2019年第11期2206-2217,共12页
【目的】通过改造谷氨酸棒杆菌JNR中双功能尿苷酰转移/去除酶GlnD,减弱尿苷酰去除酶的活性,增强NH4+的转运和利用,提高L-精氨酸的合成。【方法】本文对来源于谷氨酸棒杆菌的突变菌株JNR中的双功能尿苷酰转移/去除酶GlnD进行整合突变,采... 【目的】通过改造谷氨酸棒杆菌JNR中双功能尿苷酰转移/去除酶GlnD,减弱尿苷酰去除酶的活性,增强NH4+的转运和利用,提高L-精氨酸的合成。【方法】本文对来源于谷氨酸棒杆菌的突变菌株JNR中的双功能尿苷酰转移/去除酶GlnD进行整合突变,采用同源重组的方法将H414和D415位点突变为两个丙氨酸AA,在此菌株的基础上过量表达PII蛋白GlnK,并对其进行尿苷酰化研究,离子色谱检测摇瓶发酵过程中NH4+的浓度,并对最终的改造菌株进行连续流加发酵分析。【结果】该双功能尿苷酰转移/去除酶在谷氨酸棒杆菌中成功进行整合突变,有效减弱了尿苷酰去除酶的活性;同时过表达PII蛋白GlnK,其酰基化程度明显增强。摇瓶发酵结果表明菌株L4消耗NH4+增加,L-精氨酸产量为36.2±1.2 g/L,比对照菌株L3高出22.7%。5-L发酵罐实验结果显示改造菌株L4的L-精氨酸的产量为52.2 g/L,较野生型菌株L0提高了25.3%。【结论】谷氨酸棒杆菌合成L-精氨酸的过程中氮源是必不可少的。减弱GlnD尿苷酰去除酶的活性后,胞内尿苷酰化的GlnK-UMP增加,GlnK-UMP与氮转录调控因子AmtR结合,转运至胞内的NH4+浓度提高,促使L-精氨酸产量显著提高。 展开更多
关键词 谷氨酸棒杆菌JNR 双功能尿苷酰转移/去除酶GlnD NH4+ L-精氨酸 整合突变
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The effectiveness of sound-processing strategies on tonal language cochlear implant users:A systematic review 被引量:1
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作者 Haihong Liu Xiaoxia Peng +1 位作者 yawen zhao Xin Ni 《Pediatric Investigation》 2017年第1期32-39,共8页
Importance:Contemporary cochlear implants(CIs)are well established as a technology for people with severe-to-profound sensorineural hearing loss,with their effectiveness having been widely reported.However,for tonal l... Importance:Contemporary cochlear implants(CIs)are well established as a technology for people with severe-to-profound sensorineural hearing loss,with their effectiveness having been widely reported.However,for tonal language CI recipients,speech perception remains a challenge:Conventional signal processing strategies have been demonstrated to possibly provide insufficient information to encode tonal cues,and CI recipients have exhibited considerable deficits in tone perception.Thus,some tonal language-oriented sound-processing strategies have been introduced.The effects of available tonal language-oriented strategies on tone perception are reviewed and evaluated in this study.The results may aid in designing and improving tonal language-appropriate sound-processing strategies for CI recipients.Objective:The objective of this systematic review was to investigate the effects of tonal-language-oriented signal processing strategies on tone perception,music perception,word and sentence recognition.Methods:To evaluate the effects of tonal language-oriented strategies on tone perception,we conducted a systematic review.We searched for relevant reports dated from January 1979 to July 2017 using PubMed,Cochrane Library,EBSCO,Web of Science,EMBASE,and 4 Chinese periodical databases(CBMdisc,CNKI,VIP,andWanfang Data).Results:According to our search strategy,672 potentially eligible studies were retrieved from the databases,with 12 of these studies included in the final review after a 4-stage selection process.The majority of sound-processing strategies designed for tonal language were HiResolutionwith Fidelity 120(HiRes 120),fine structure processing,temporal fine structure(TFS),and C-tone.Generally,acute or short-term comparisons between the tonal language-oriented strategies and the conventional strategy did not reveal statistically significant differences in speech perception(or show a small improvement).However,a tendency toward improved tone perception and subjectively reported overall preferred sound quality was observed with the tonal language-oriented strategies.Interpretation:Conventional signal processing strategies typically provided very limited F0 information via temporal envelopes delivered to the stimulating electrodes.In contrast,tonal language-oriented coding strategies attempted to present more spectral information and TFS cues required for tone perception.Thus,a tendency of improved performance in tonal language perception in CI users was shown. 展开更多
关键词 cochlear implant fine structure strategy TONE
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