作者希望，感谢Emilija仁科和珍妮特于提供技术援助。 DCN的支持，补助金从美国国防部（DR080205，DM102823，OR09055，OR090059），，。 RDH的支持，马里兰州农业试验站，在细胞和分子生物学的NIH训练的资助。

1。确定加热条件首先，必须通过实验确定最佳的温育温度和时间，在测定中使用的加热步骤。对于我们的PlyC模型，重要的是要注意， 大肠杆菌大肠杆菌对单独的表达质粒共转化与plyCA和plyCB基因已被证明，以形成一个全功能的PlyC全酶6。适于从在文献中提供的实施例12-16的96孔微量滴定板的制备以及作为细胞生长条件和随后副本电镀技术。从以前的热灭活实验的结果决定活动急剧下降，在短期在超过生理温度（未发表的观察）的环境中孵化，孵化时间30分钟将适合此法。的最佳培养温度为PlyC阐明通过下面的步骤: <ol><li>陈德良sform表达构建pBAD24:plyCA（安培）到主管E.大肠杆菌菌株DH5αpBAD33:plyCB（CM）。 </li><li>板上的Luria-Bertani（LB）补充氨苄青霉素（100微克/毫升）和氯霉素（35微克/毫升）的琼脂平板上的转化体。一夜之间孵育板在37°C。 </li><li>用无菌牙签，单个菌落接种到每个排孔（ 图2a）中的无菌的，清晰的，平底96孔，带盖的微量滴定板，其中包含200微升补充有氨苄青霉素和氯霉素的LB。 </li><li>可以安全地放置在96孔微量滴定板在37℃下摇床和长出的细菌在300rpm过夜。 </li><li>找回的96孔微量滴定板的37℃下摇床和副本板到一个新的96孔微量滴定板，如下所示: <ol class="lalpha"><li>加入180μl辅以氨苄青霉素和氯霉素的LB副本板的各孔。 </li><li>从原版20μl的细菌转移到相应的井在副本板。这将导致在初始OD 600为〜0.5。 </li></ol></li><li>安全地将副本板在37度，Ç颤抖的孵化器和孵化1小时，在300转板，然后添加inductant。在PBAD表达系统的情况下，inductant是0.25％阿拉伯糖。其他表达系统可能需要不同的inductants。板放置在37℃下摇床和摇一个额外的4小时，以允许用于蛋白质表达在300rpm。表达水平通常介于10-20微克的PlyC的。 </li><li>一旦蛋白的表达已经结束，检索的副本板和颗粒的细菌在冷冻离心机，包含摆动斗转子，适合96孔酶标板96孔酶标板。在3,000 rpm下离心10分钟，在室温下。</li><li>慢慢地翻转酶标板取出介质上清，轻轻地调迁的媒体。 </li><li>向每孔加入50μl的第二B-PER细菌蛋白抽提试剂溶解细胞。板在室温下孵育20分钟。 </li><li>增大音量，在各孔中，通过加入120微升70微升磷酸盐缓冲盐水（PBS），PH值7.2。 </li><li>沉淀不溶的细胞碎片，通过纺丝板以3,000 rpm，在冷冻离心机在4℃下10分钟。 </li><li>水溶性粗提液110微升转移到一个96孔的热循环仪板相应的孔中。 </li><li>使用预定的孵化时间为30分钟，暴露的可溶性裂解目前居住在96个热循环仪板了广阔的梯度温度范围15-20℃。注意，目标是要确定在什么温度下一个特定的酶失去了&gt; 95％的催化活性。 </li><li>孵化，孵化后的96孔温度循环器板在4℃下5分钟，从96孔的热循环仪板100微升的可溶性裂解物转移到其相应的在最后的96孔微量滴定板的井位。 </li><li>随着一个12通道multipipettor，每孔加入100μl的GAS菌株D471。请注意，D471的细胞原本是从过夜培养冻干并重新悬浮用PBS pH值7.2〜2.0，得到的OD 600。 </li><li>立即放置在96孔板上，在微孔板分光光度计和通过测量的OD 600为20分钟，每15秒监测的酶动力学。被定义为在非允许温度下，对应于井，缺乏光密度的变化（ΔOD≤0.1）的最低温度孵育。 </li></ol>一个宽的温度屏幕之后执行，以确定非允许温度下，可以重复上述步骤，在一个更​​窄的范围内的温度（5℃-10℃），以澄清感兴趣的酶的精确的非允许温度下。请注意，非允许温度下，在该测定中确定比通过其他方式阐明的熔融温度可能会有所不同，由于体积差异，浓度等 2。生成的突变体库以进行筛选的突变体库的创建涉及随机纳入由以最小的核苷酸偏压在plyCA基因，使用如下的GeneMorph II随机诱变试剂盒的一个容易出错的DNA聚合酶的突变: <ol><li>设计相似的熔融温度（Tm）的55-72℃下与给出的限制性位点的5&#39;和3&#39;末端的plyCA基因之间的核苷酸引物。 </li><li>由于所需的突变率是2-3核苷酸每plyCA的 （1.4kb的），使用PCR反应组分的浓度，以及低的突变f由生产商推荐的条件的热循环仪requencies（0-4.5每KB）。 </li><li>的的诱变plyCA基因克隆到表达载体pBAD24。 </li><li>变换的的构造成DH5αpBAD33:plyCB背景和板补充与氨苄青霉素和氯霉素的LB琼脂平板上的转化体。 </li><li>此外，变换和板DH5αpBAD33:plyCB pBAD24含有的WT plyCA基因的表达载体。从这个板块的殖民地将作为筛选过程的控制。 </li></ol> 3。 96孔微孔板的制备及细胞生长条件<ol><li>填充在96孔微量滴定板的各孔中，用200μl补充有氨苄青霉素和氯霉素的LB。 </li><li>微量滴定板的原理图（ 图2b）之后，小心地从过夜的琼脂平皿上选择一个单独的菌落用无菌牙签和接种的细菌，在指定的96孔微量滴定解放军德。这是必要的，以确保只有一个殖民地，每孔接种。 </li><li>摇动牢固地固定的96孔微量滴定板在37℃下在300 rpm的转速下过夜</li></ol> 4。副本电镀，蛋白表达的诱导和裂解液的制备<ol><li>按照步骤1.5-1.11一节"确定最佳的加热条件"的一个修改。存储的原始板，在4℃下后的副本电镀步骤已经结束。 </li><li>步后1.11，转移除了阳性对照孔A1-D1的96孔的热循环仪板的相应孔中的可溶性的粗裂解物到110微升。关于与阳性对照溶胞产物（ 即裂解物，不加热），转移到相应的井在一个新的96孔微量滴定板，将作为最终测定板的实验和存储在冰上的溶胞产物的100μl的。 </li></ol> 5。可溶性细胞裂解液热处理<ol><li>热阴性对照和突变体可溶性裂解液目前只限于在步骤1中确定在优化非许可孵化温度为30分钟，在热循环仪96孔热循环仪板。 </li><li>非允许温度下温育后，在4℃下孵育96以及热循环仪板5分钟。 </li><li>将100微升的可溶性裂解物从96孔的热循环仪的板，其在最后的96孔微量滴定测定板已经含有可溶性裂解物的阳性对照相同的井位。 </li><li>随着一个12通道multipipettor，每孔加入100μl的GAS菌株D471。在微孔板分光光度计立即将板。 </li><li>监视的酶动力学通过测量OD 600每15秒20分钟。 <ol class="lalpha"><li>甲PlyC与进展的热行为的变体被定义为一个结构中，可降低50％原来的光学密度在少于900秒，在该非允许温度。此外，阳性对照（ 即非加热，WT PlyC）需要以显示WT的催化活性（ 的t 1/2≤100秒）和阴性对照（ 即加热，WT PlyC）应该是没有活性的。 </li></ol></li><li>一旦PlyC变种与进展热行为被识别，检索储存在4℃和接种细菌从个人以及特定的突变成与氨苄青霉素和氯霉素的新鲜LB培养基中的兴趣的原始板。过夜生长的接种物，在37°C。 </li><li>从文化的提取和纯化质粒DNA，然后进行测序，以确定的核苷酸突变，推测增强的热性能PlyCA提交。此外，补充从过夜培养的小等分试样用10％甘油和存储在-80℃下以供进一步使用。 </li></ol>

<ol>
	<li>Jackel, C., Kast, P., Hilvert, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+design+by+directed+evolution.">Protein design by directed evolution.</a> Annual review of biophysics. 37, 153-173 (2008).</li><li>Liu, L., Li, Y., Liotta, D., Lutz, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Directed+evolution+of+an+orthogonal+nucleoside+analog+kinase+via+fluorescence-activated+cell+sorting.">Directed evolution of an orthogonal nucleoside analog kinase via fluorescence-activated cell sorting.</a> Nucleic acids research. 37, 4472-4481 (2009).</li><li>Fischetti, V. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacteriophage+lysins+as+effective+antibacterials.">Bacteriophage lysins as effective antibacterials.</a> Curr. Opin. Microbiol. 11, 393-400 (2008).</li><li>Fischetti, V. A., Nelson, D., Schuch, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reinventing+phage+therapy:+are+the+parts+greater+than+the+sum.">Reinventing phage therapy: are the parts greater than the sum.</a> Nat. Biotechnol. 24, 1508-1511 (2006).</li><li>Loessner, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacteriophage+endolysins--current+state+of+research+and+applications.">Bacteriophage endolysins--current state of research and applications.</a> Curr. Opin. Microbiol. 8, 480-487 (2005).</li><li>Nelson, D., Schuch, R., Chahales, P., Zhu, S., Fischetti, V. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PlyC:+A+multimeric+bacteriophage+lysin.">PlyC: A multimeric bacteriophage lysin.</a> Proc. Natl. Acad. Sci. U.S.A. 103, 10765-10770 (2006).</li><li>Nelson, D., Loomis, L., Fischetti, V. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prevention+and+elimination+of+upper+respiratory+colonization+of+mice+by+group+A+streptococci+using+a+bacteriophage+lytic+enzyme.">Prevention and elimination of upper respiratory colonization of mice by group A streptococci using a bacteriophage lytic enzyme.</a> Proc. Natl. Acad. Sci. U.S.A. 98, 4107-4112 (2001).</li><li>Filatova, L. Y., Becker, S. C., Donovan, D. M., Gladilin, A. K., Klyachko, N. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=LysK,+the+enzyme+lysing+Staphylococcus+aureus+cells:+specific+kinetic+features+and+approaches+towards+stabilization.">LysK, the enzyme lysing Staphylococcus aureus cells: specific kinetic features and approaches towards stabilization.</a> Biochimie. 92, 507-513 (2010).</li><li>Varea, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+and+thermodynamic+characterization+of+Pal,+a+phage+natural+chimeric+lysin+active+against+pneumococci.">Structural and thermodynamic characterization of Pal, a phage natural chimeric lysin active against pneumococci.</a> J. Biol. Chem. 279, 43697-43707 (2004).</li><li>Sanz, J. M., Garcia, J. L., Laynez, J., Usobiaga, P., Menendez, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermal+stability+and+cooperative+domains+of+CPL1+lysozyme+and+its+NH2-+and+COOH-terminal+modules.+Dependence+on+choline+binding.">Thermal stability and cooperative domains of CPL1 lysozyme and its NH2- and COOH-terminal modules. Dependence on choline binding.</a> J. Biol. Chem. 268, 6125-6130 (1993).</li><li>Anderson, G., Scott, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+product+shelf+life+and+activation+energy+for+five+drugs+of+abuse.">Determination of product shelf life and activation energy for five drugs of abuse.</a> Clin. Chem. 37, 398-402 (1991).</li><li>Kim, G. J., Cheon, Y. H., Kim, H. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Directed+evolution+of+a+novel+N-carbamylase/D-hydantoinase+fusion+enzyme+for+functional+expression+with+enhanced+stability.">Directed evolution of a novel N-carbamylase/D-hydantoinase fusion enzyme for functional expression with enhanced stability.</a> Biotechnol. Bioeng. 68, 211-217 (2000).</li><li>Koutsioulis, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Directed+evolution+on+the+cold+adapted+properties+of+TAB5+alkaline+phosphatase.">Directed evolution on the cold adapted properties of TAB5 alkaline phosphatase.</a> Protein Eng. Des. Sel. 21, 319-327 (2008).</li><li>McCarthy, J. K., Uzelac, A., Davis, D. F., Eveleigh, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+catalytic+efficiency+and+active+site+modification+of+1,4-beta-D-glucan+glucohydrolase+A+from+Thermotoga+neapolitana+by+directed+evolution.">Improved catalytic efficiency and active site modification of 1,4-beta-D-glucan glucohydrolase A from Thermotoga neapolitana by directed evolution.</a> J. Biol. Chem. 279, 11495-11502 (2004).</li><li>Ren, C., Chen, T., Zhang, J., Liang, L., Lin, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+evolved+xylose+transporter+from+Zymomonas+mobilis+enhances+sugar+transport+in+Escherichia+coli.">An evolved xylose transporter from Zymomonas mobilis enhances sugar transport in Escherichia coli.</a> Microbial cell factories. 8, 66 (2009).</li><li>Tsuzuki, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermostable+mutants+of+the+photoprotein+aequorin+obtained+by+in+vitro+evolution.">Thermostable mutants of the photoprotein aequorin obtained by in vitro evolution.</a> J. Biol. Chem. 280, 34324-34331 (2005).</li><li>Eijsink, V. G., Gaseidnes, S., Borchert, T. V., vanden Burg, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Directed+evolution+of+enzyme+stability.">Directed evolution of enzyme stability.</a> Biomolecular engineering. 22, 21-30 (2005).</li><li>Kumar, S., Nussinov, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+do+thermophilic+proteins+deal+with+heat.">How do thermophilic proteins deal with heat.</a> Cell. Mol. Life Sci. 58, 1216-1233 (2001).</li><li>Hibbert, E. G., Dalby, P. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Directed+evolution+strategies+for+improved+enzymatic+performance.">Directed evolution strategies for improved enzymatic performance.</a> Microb. Cell Fact. 4, 1475-2859 (2005).</li><li>Rasila, T. S., Pajunen, M. I., Savilahti, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Critical+evaluation+of+random+mutagenesis+by+error-prone+polymerase+chain+reaction+protocols,+Escherichia+coli+mutator+strain,+and+hydroxylamine+treatment.">Critical evaluation of random mutagenesis by error-prone polymerase chain reaction protocols, Escherichia coli mutator strain, and hydroxylamine treatment.</a> Anal. Biochem. 388, 71-80 (2009).</li><li>Wong, T. S., Roccatano, D., Zacharias, M., Schwaneberg, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+statistical+analysis+of+random+mutagenesis+methods+used+for+directed+protein+evolution.">A statistical analysis of random mutagenesis methods used for directed protein evolution.</a> J. Mol. Biol. 355, 858-871 (2006).</li><li>Arnold, F. H., Wintrode, P. L., Miyazaki, K., Gershenson, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+enzymes+adapt:+lessons+from+directed+evolution.">How enzymes adapt: lessons from directed evolution.</a> Trends in biochemical sciences. 26, 100-106 (2001).</li></ol>

没有利益冲突的声明。

该协议中，在图1中所概述，提出了一个96孔微量滴定板的方法，它允许一个利用定向进化增加任何溶菌酶的热稳定性。通过一个容易出错的DNA聚合酶的使用，人们可以引入随机突变，增加整体的动力学稳定性的翻译的溶菌分子的利益，这通常是由于分子重组组成的增加静电，二硫桥和疏水性相互作用，产生改善分子齐聚状态提出了更高的17日至18日的的表面电荷网络或加固包装，增强了修改。核苷酸突变引入后，一个广泛的筛选程序，然后使用，以确定突变是热有益。代表结果是根据上一轮的随机突变。在现实中，它已被认为随机诱变的至少三个连续的轮，每个使用最强大的突变体作为引线的酶，然后通过DNA改组是适合于这些类型的定向进化的热行为的研究2。 重要的是要了解，而该协议的识别，增强动力稳定性的突变，这些变异体的不一定是增加了热稳定性。的分子被认为是热稳定的，它有能力在一个较高的温度下保持其结构时。然而，在测定中提出，没有突变的溶胞产物的残余活性测定在相同温度下，他们最初孵育在所述热处理步骤期间，从而可以选择的突变促进复性，而不是增强的热稳定性19。虽然我们推断热行为作为热稳定性的指标，真正的热稳定性，必须凭经验测定生物物理学ICAL方法，如圆二色性（CD），差示扫描量热法（DSC）和差示扫描荧​​光（DSF）。从CD和DSF实验的初步数据表明，从介绍的方法确定的几个候选人确实显示进展的热稳定性（数据未示出）。 虽然这里介绍的方法是具体实施热行为增加PlyC，这同样的方法可以额外地提高热其他溶菌酶的活性有一些小的改变，如缓冲剂，突变率，加热条件和表达系统的变量。的一个关键的变量与该测定涉及的容易出错的DNA聚合酶的碱基突变率。我们选择使用容易出错的Mutazyme II DNA聚合酶在我们的定向进化分析由于实验证据表明这显示特定的酶量最少的偏见与问候中，核苷酸是随机掺入的感兴趣的基因时相比，其他的随机诱变技术，如使用羟胺，赋值函数E.大肠杆菌和其他容易出错的DNA polyermases 20。在一般情况下，较低的突变率往往是更可取的，原因有二。首先，工程热稳定性的蛋白质通常包括相对较少的氨基酸取代。高突变率可能会导致特定分子结构的错误折叠和功能的差异，才能最后导致巨大的结构性改变。例如，甘氨酸和脯氨酸残基的掺入可以破坏α-螺旋的二级结构21。第二，高核苷酸的突变率增加成功的机会将提前终止密码子，从而导致生物活性的分子，在截断。在一般情况下，是优选的突变率较低，因为较低的错误率的结果，在储液器适应性突变的功能明显下降，而较高的突变率产生中性或有害的突变22。 每一轮的随机突变，另一个关键的变量，必须优化涉及到孵化温度在筛选过程中使用。选择的实验性非允许温度下是比较具有挑战性。我们最初使用的孵化温度为10°C比非许可温度PlyC的，但是在3000突变体的筛选，我们无法识别任何有利的突变。牢记定向进化方法包括依次进行识别具有加性效应的有益的氨基酸替换，它被确定不那么严格的温度下，应使用在筛选过程中，即使它产生假阳性的机会增加。因此，我们使用了一个孵化温度只有几摄氏度以上的非permiss香港专业教育学院的温度和再筛选选定的候选人，以排除假阳性。 我们决定利用的孵化温度，是不是太温带（≤1℃，高于最低的非允许温度下），反之不是太苛刻（≥5°C高于最低的非允许温度下）。理想的温度，我们决定在这个特殊的检测使用的是一个温和的2°C高于实验确定的非许可温度。选择太温和的温度下，会导致高得多的假阳性比〜20％，我们观察到（ 表I）的识别率时，使用一个适度的孵化温度。此外，使用过于苛刻的孵化温度，最终可能会导致无法识别突变体具有显着增强的热性能。例如，使用的孵化温度≥5℃下将有导致无法识别看好29C3突变体以及大多数其他候选人在第一轮的筛选选择。 在总结中，我们提供了一个协议，工程溶菌酵素，获得增强的动力学稳定性。此外，这种相同的测定，未经加热步骤，可以使用催化活性的突变，增加屏幕。增强的催化活性和热稳定性是一个重要的发展障碍，面对任何治疗酶。虽然此协议的细节是特定的细胞内溶素PlyC，该方法可以适于任何溶菌酶只有一些改动。我们提出了初步结果只从第一轮诱变验证该功能的测定，导致产生显著大小分子的热稳定性，增加的突变，在执行和识别。

<table border="1"><tbody><tr><td> 的试剂的名称 </td><td> 公司 </td><td> 目录编号 </td></tr><tr><td> B-PER II细菌蛋白抽提试剂</td><td> Thermo Scientific的</td><td> 78260 </td></tr><tr><td> GeneMorph II随机突变试剂盒</td><td>安捷伦科技公司</td><td> 200500 </td></tr><tr><td>清除96孔，平底微孔板盖</td><td> BD真空采血管医学实验医学</td><td> 353072 </td></tr><tr><td> 96好Nonskir​​ted之PCR板</td><td> Fisher Scientific则</td><td> 14-230-232 </td></tr><tr><td>水平转子</td><td> Eppendorf公司</td><td> A-2-DWP </td></tr><tr><td>氨苄西林钠</td><td> Fisher Scientific则</td><td> BP1760 </td></tr><tr><td>氯霉素</td><td> Fisher Scientific则</td><td> BP904 </TD&gt; </tr><tr><td>阿拉伯糖</td><td> Fisher Scientific则</td><td> BP2504 </td></tr><tr><td> pBAD24表达载体的构建</td><td> ATCC </td><td> 87399 </td></tr><tr><td> pBAD33表达载体的构建</td><td> ATCC </td><td> 87402 </td></tr></tbody></table>

a new screening method for the directed evolution of thermostable bacteriolytic enzymes

定向进化被定义为利用自然选择的方法，以便工程师来获得特别是不相关联的属性中的蛋白质性质的蛋白质。文学提供了大量的关于实施定向进化的例子，成功地改变分子的特异性和催化1。利用定向进化，而 ​​不是更理性为基础的方法对分子工程的主要优点涉及到的数量和多样性的变种，可以筛选2。定向进化的一个可能的应用涉及溶菌酶，如内溶素的结构稳定性的改善。噬菌体编码和表达的一个重要的共价键（ 即细胞壁的肽聚糖）的细菌内溶水解，产生的子代病毒在宿主细胞裂解和解放。值得一提的是，这些酶具有的能力，外在诱导裂解的易感已验证IBLE细菌噬菌体并且在没有在体外和体内对他们的治疗潜力3-5。我们的定向进化研究的主题涉及PlyC内溶素，它是由PlyCA和PlyCB亚基6。纯化和添加非本质当，PlyC全酶溶解在几秒钟内的A组链球菌（GAS）以及其他链球菌群体的而且已经通过验证在活体内对气体7。显着，监测后残余酶动力学，高温下孵化提供了明显的证据，PlyC失去催化活性突然在45°C，这表明一个短期治疗的保质期，这可能会限制进一步发展这种酶。进一步的研究揭示缺乏热稳定性只观察为PlyCA亚基，，而PlyCB亚基是稳定的高达〜90℃（未发表的观察）。除了PlyC，有s许多研究文献中的例子，描述了耐热性质的内。例如， 葡萄球菌溶素LysK和肺炎链球菌内溶CPL-1和好朋友自发失去活性，在42°C，43.5°C和50.2°C，8-10。根据Arrhenius方程，其中涉及的化学反应的速率在 ​​特定的系统中存在的温度，增加的热稳定性将与增加货架寿命11。为此，定向进化已被证明是一个有用的工具，改变自然界中各种分子的热活动的，但从来没有成功利用这个特殊的技术溶菌酶的研究。同样，成功的账目结构的稳定性，这个特定的类抗菌药物的进展完全是不存在的。在这段视频中，我们采用了一种新的方法，使用错误-PR一种DNA聚合酶，然后用96孔微量滴定板格式，以确定突变的PlyCA亚基的酶动力学稳定性的增加（ 图1）相关联的PlyC链球菌细胞内溶素的优化的筛选过程。结果只是随机诱变的一个轮后，建议的方法是产生保留的两倍以上时相比，野生型（WT）PlyC升高的温度下处理后的残余活性的PlyC变种。

在结束了第一轮的随机突变，超过6000 PlyC的突变体的筛选，共35突变可能增加的热行为进行了鉴定，选择和测序。总结在表Ⅰ中 ，基因组分析，表明35候选人，7的构造包含的WT PlyCA序列翻译的电平，对应于由试验确定的误报。的余下的28名候选人，突变范围是1至6个碱基的突变与平均突变率的2.75的每plyCA基因，它是在2-3的碱基突变的目标的范围内，我们核苷酸。在翻译水平，这个特定的碱基突变范围和频率产生范围为1至5个氨基酸的氨基酸变异，与平均1.9每PlyCA多肽的氨基酸突变的突变率。 与至少一个氨基酸mutat的28个候选离子，这些突变构建四个随机选择验证的定向进化方法的广泛的筛选过程中确实正常作进一步鉴定。的突变PlyC酶进行纯化至&gt; 95％的均匀性，根据SDS-PAGE上分析，如先前描述的6-7。 WT PlyC和四个PlyC各突变体的酶动力学，其特征在于以相等的摩尔浓度纯化的酶的孵育后，在不同的温度升高。活动监测加入D471气体后，通过测量20分钟，每15秒，在600 nm的光密度。活性定义为热孵化后的酶的剩余的最高速度。随机挑选的四名候选人作进一步鉴定，突变体29C3表现出增强的热性能。 WT PlyC和29C3的热行为的影响在不同的温度下，同时温育并在PBS pH 7.2的活性测定在80 nM和40 nM的浓度，分别。 45-50℃的培养实验（ 图3）进行热循环仪中，在薄壁板在96孔热循环仪的总体积为120微升的样品孵育。 35℃，40℃和45℃下进行培养实验（ 图4和图5）中的热块在1.5ml微量离心管中的总体积为1.3毫升的样品孵育。所有实验均在一式三份。 WT PlyC和29C3没有表现出显着性差异，在动力学稳定性，在室温（25℃）作为描绘在图3中的第一组的酒吧。然而，从温度从45-50℃下30分钟的孵育后短期，29C3活性显着地大于在各温度点的WT构造特定的活性。例如，WT PlyC显示，44％的活性损失45.2℃，而29C3表明只有2％的损失，在相同温度下的活性。 孵育的长期研究，比较两个WT PlyC和29C3的残存活性，另外进行，在35℃和40℃的涉及在24和48小时的时间点测量的残余活性。 29C3显示在35°C，41％和176％活性高于WT PlyC在24和​​48小时的孵化时间点，分别为（ 图4a）。 29C3显示在40°C，28％和107％活性高于WT PlyC在24和​​48小时的孵化时间点，分别为（ 图4b）。 WT PlyC和29C3的残余活性也被监测，每20分钟共3小时，在45℃下，WT PlyC只能保留21％的活性，而29C3在此温度下保温3小时后能保留46％的活性。 WT PlyC和29C3的半衰期（的t 1/2）分别为67和147分钟，分别，建议<html> 29C3 ING，有2.2倍的增长在动力学稳定性，在45℃（ 图5）。 <table border="1"><tbody><tr><td>总计第1轮候选人</td><td> 35 </td></tr><tr><td>考生WT PlyCA序列</td><td> 7 </td></tr><tr><td>考生≥1氨基酸突变</td><td> 28 </td></tr><tr><td> -平均核苷酸突变率（NT / plyCA的 ） </td><td> 2.75 </td></tr><tr><td> - 核苷酸变异范围（NT） </td><td> 1-6 </td></tr><tr><td> - 平均氨基酸的突变率（AA / PlyCA） </td><td> 1.9 </td></tr><tr><td> - 氨基酸变异范围（AA） </td><td> 1-5 </td></tr></tbody></table> 表1。候选人基因组分析。 pload/4216/4216fig1highres.jpg"/&gt; 图1。定向进化分析方法。定向进化，一个人开始，与铅酶，将WT PlyC的第一轮。包含随机公正的plyCA基因的核苷酸突变的PlyC突变体库，然后构建一个容易出错的DNA聚合酶，克隆到表达载体pBAD24，转化到E.大肠杆菌菌株DH5α中已经含有pBAD33:plyCB个别的转化体接种到其自身特定的孔的96孔微量滴定板。通过广泛的筛选过程中，个别PlyC催化活性的突变体，在非容许的温度下温育后，被分类为动力学稳定性增强的突变体。 Theconstruct显示最进展的热性能，将因而成为铅的酶为下一轮的随机诱变。总体来说，有三个完整的轮拟人米突变，DNA改组在溶菌分子的与演化的热行为。 <a href="http://www.jove.com/files/ftp_upload/4216/4216fig1large.jpg" target="_blank">点击此处查看大图</a> 。 <img alt="图2" src="/files/ftp_upload/4216/4216fig2.jpg" /> 图2。定向进化测定96孔微量滴定板的模板的微量滴定板的最佳的加热条件下的测定期间的示意图（ 图2a）包括一个单一的父母WT PlyC克隆接种到微量滴定板的每一行的。的微量滴定板的示意图（ 图2b）的突变体的筛选期间，包括在第1列中的每个孔中接种，以及独特的父母WT PlyC克隆接种各孔列中的2-12具有鲜明PlyC突变克隆。被指定为家长积极控制，共同井A1-D1nsist WT PlyC结构不暴露在非允许的温度孵化。 E1-H1井被指定为负的家长控制功能，其中包括暴露在非允许的温度孵化的的WT PlyC结构。 <img alt="图3" src="/files/ftp_upload/4216/4216fig3.jpg" /> 图3。残余活性的动力学分析，比较WT PlyC和29C3酶被纯化至均一，并温育30分钟，在热循环仪中，以相等的摩尔浓度，在任一室温下或在范围从45-50℃的温度梯度酶的活性与特定温度下孵化后显示的最大速度。随着异常为25℃和47.7℃，在每个温度下的变化在WT和29C3之间的活动相关的p-值&lt;0.05。所有的数据被报告为三个独立实验的平均值±SEM。 </p&gt; <img alt="图4" src="/files/ftp_upload/4216/4216fig4.jpg" /> 图4。剩余活性动力学分析比较WT PlyC 29C3在35℃和40℃。平等摩尔浓度纯化的WT PlyC和29C3孵育的热块中，在35℃（ 图4a）或40℃（ 图4b）。在24和48小时的时间点，测定残留的酶活性。每种构建所显示的活性，被归一化到在时间点零显示的最大速度。活性在WT和29C3之间在每一个温度和时间点相关的变化的p-值&lt;0.05。所有的数据被报告为三个独立实验的平均值±SEM。 <img alt="图5" src="/files/ftp_upload/4216/4216fig5.jpg" /> 图5。剩余活性动力学分析比较WT PlyC 29C3在45°C的平等纯化WT PlyC和29C3的摩尔浓度的热块中孵育在45℃，测定残留的酶活性为3小时，每20分钟。每种构建所显示的活性，被归一化到在时间点零显示的最大速度。与异常的数据点在20分钟，在每个时间点的变化在WT和29C3之间的活性相关性的p-值&lt;0.05。所有的数据被报告为三个独立实验的平均值±SEM。

Watch this Scientific Journal Video about A New Screening Method for the Directed Evolution of Thermostable Bacteriolytic Enzymes at JoVE.com

耐热溶菌酶定向进化的新筛选方法- 中国优秀硕士学位论文全文数据库免疫学和感染|视频

A New Screening Method for the Directed Evolution of Thermostable Bacteriolytic Enzymes

热稳定性工程领域的一种新型的定向进化方法的具体开发，从而验证溶菌酵素。随机诱变只有一轮中，演进式溶菌酶，PlyC 29C3，显示后大于两倍的残留活性相比升高的温度下温育后的野生型蛋白。

耐高温溶菌酶的定向进化的一个新的筛选方法

Directed evolution is defined as a method to harness natural selection in order to engineer proteins to acquire particular properties that are not ...

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17.8K 次观看.  University of Maryland. 热稳定性工程领域的一种新型的定向进化方法的具体开发，从而验证溶菌酵素。随机诱变只有一轮中，演进式溶菌酶，PlyC 29C3，显示后大于两倍的残留活性相比升高的温度下温育后的野生型蛋白。

视频: A New Screening Method for the Directed Evolution of Thermostable Bacteriolytic Enzymes

Particle Agglutination Method for Poliovirus Identification

In the Global Polio Eradication Initiative, laboratory diagnosis plays a critical role by isolating and identifying PV from the stool samples of acute flaccid paralysis (AFP) cases. In the World Health Organization (WHO) Global Polio Laboratory Network, PV isolation and identification are currently being performed by using cell culture system and real-time RT-PCR, respectively. In the post-eradication era of PV, simple and rapid identification procedures would be helpful for rapid confirmation of polio cases at the national laboratories. In the present study, we will show the procedure of novel PA assay developed for PV identification. This PA assay utilizes interaction of PV receptor (PVR) molecule and virion that is specific and uniform affinity to all the serotypes of PV. The procedure is simple (one step procedure in reaction plates) and rapid (results can be obtained within 2 h of reaction), and the result is visually observed (observation of agglutination of gelatin particles).

A recently developed novel particle agglutination (PA) assay utilizing virus receptor molecule allowed a rapid and easy identification of poliovirus (PV). In this article, we will show the procedure for the PA assay for PV identification.

脊髓灰质炎病毒识别粒子凝集法

In the Global Polio Eradication Initiative, laboratory diagnosis plays a critical role by isolating and identifying PV from the stool samples of acute ...

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免疫与感染

Selection of Plasmodium falciparum Parasites for Cytoadhesion to Human Brain Endothelial Cells

Most human malaria deaths are caused by blood-stage Plasmodium falciparum parasites. Cerebral malaria, the most life-threatening complication of the disease, is characterised by an accumulation of Plasmodium falciparum infected red blood cells (iRBC) at pigmented trophozoite stage in the microvasculature of the brain2-4. This microvessel obstruction (sequestration) leads to acidosis, hypoxia and harmful inflammatory cytokines (reviewed in 5). Sequestration is also found in most microvascular tissues of the human body2, 3. The mechanism by which iRBC attach to the blood vessel walls is still poorly understood.
The immortalized Human Brain microvascular Endothelial Cell line (HBEC-5i) has been used as an in vitro model of the blood-brain barrier6. However, Plasmodium falciparum iRBC attach only poorly to HBEC-5i in vitro, unlike the dense sequestration that occurs in cerebral malaria cases. We therefore developed a panning assay to select (enrich) various P. falciparum strains for adhesion to HBEC-5i in order to obtain populations of high-binding parasites, more representative of what occurs in vivo.
A sample of a parasite culture (mixture of iRBC and uninfected RBC) at the pigmented trophozoite stage is washed and incubated on a layer of HBEC-5i grown on a Petri dish. After incubation, the dish is gently washed free from uRBC and unbound iRBC. Fresh uRBC are added to the few iRBC attached to HBEC-5i and incubated overnight. As schizont stage parasites burst, merozoites reinvade RBC and these ring stage parasites are harvested the following day. Parasites are cultured until enough material is obtained (typically 2 to 4 weeks) and a new round of selection can be performed. Depending on the P. falciparum strain, 4 to 7 rounds of selection are needed in order to get a population where most parasites bind to HBEC-5i. The binding phenotype is progressively lost after a few weeks, indicating a switch in variant surface antigen gene expression, thus regular selection on HBEC-5i is required to maintain the phenotype.
In summary, we developed a selection assay rendering P. falciparum parasites a more "cerebral malaria adhesive" phenotype. We were able to select 3 out of 4 P. falciparum strains on HBEC-5i. This assay has also successfully been used to select parasites for binding to human dermal and pulmonary endothelial cells. Importantly, this method can be used to select tissue-specific parasite populations in order to identify candidate parasite ligands for binding to brain endothelium. Moreover, this assay can be used to screen for putative anti-sequestration drugs7.

Selection of Plasmodium falciparum Parasites for Cytoadhesion to Human Brain Endothelial Cells

An in vitro model for cerebral malaria sequestration is described1. Plasmodium falciparum infected red blood cells are selected for binding to immortalized human brain microvascular endothelial cells. The selected parasites show a distinct phenotype. The selection process can be applied using various P. falciparum strains and endothelial cell lines.

选择恶性疟原虫</emCytoadhesion>寄生虫对人脑血管内皮细胞

Most human malaria deaths are caused by blood-stage Plasmodium falciparum parasites. Cerebral malaria, the most life-threatening complication of the ...

A Primary Neuron Culture System for the Study of Herpes Simplex Virus Latency and Reactivation

Herpes simplex virus type-1 (HSV-1) establishes a life-long latent infection in peripheral neurons. This latent reservoir is the source of recurrent reactivation events that ensure transmission and contribute to clinical disease. Current antivirals do not impact the latent reservoir and there are no vaccines. While the molecular details of lytic replication are well-characterized, mechanisms controlling latency in neurons remain elusive. Our present understanding of latency is derived from in vivo studies using small animal models, which have been indispensable for defining viral gene requirements and the role of immune responses. However, it is impossible to distinguish specific effects on the virus-neuron relationship from more general consequences of infection mediated by immune or non-neuronal support cells in live animals. In addition, animal experimentation is costly, time-consuming, and limited in terms of available options for manipulating host processes. To overcome these limitations, a neuron-only system is desperately needed that reproduces the in vivo characteristics of latency and reactivation but offers the benefits of tissue culture in terms of homogeneity and accessibility.
Here we present an in vitro model utilizing cultured primary sympathetic neurons from rat superior cervical ganglia (SCG) (Figure 1) to study HSV-1 latency and reactivation that fits most if not all of the desired criteria. After eliminating non-neuronal cells, near-homogeneous TrkA+ neuron cultures are infected with HSV-1 in the presence of acyclovir (ACV) to suppress lytic replication. Following ACV removal, non-productive HSV-1 infections that faithfully exhibit accepted hallmarks of latency are efficiently established. Notably, lytic mRNAs, proteins, and infectious virus become undetectable, even in the absence of selection, but latency-associated transcript (LAT) expression persists in neuronal nuclei. Viral genomes are maintained at an average copy number of 25 per neuron and can be induced to productively replicate by interfering with PI3-Kinase / Akt signaling or the simple withdrawal of nerve growth factor1. A recombinant HSV-1 encoding EGFP fused to the viral lytic protein Us11 provides a functional, real-time marker for replication resulting from reactivation that is readily quantified. In addition to chemical treatments, genetic methodologies such as RNA-interference or gene delivery via lentiviral vectors can be successfully applied to the system permitting mechanistic studies that are very difficult, if not impossible, in animals. In summary, the SCG-based HSV-1 latency / reactivation system provides a powerful, necessary tool to unravel the molecular mechanisms controlling HSV1 latency and reactivation in neurons, a long standing puzzle in virology whose solution may offer fresh insights into developing new therapies that target the latent herpesvirus reservoir.

The protocol describes an efficient and reproducible model system to study herpes simplex virus type 1 (HSV-1) latency and reactivation. The assay employs homogenous sympathetic neuron cultures and allows for the molecular dissection of virus-neuron interactions using a variety of tools including RNA interference and expression of recombinant proteins.

神经元的初步培养体系的研究疱疹病毒潜伏期和活化

Herpes simplex virus type-1 (HSV-1) establishes a life-long latent infection in peripheral neurons. This latent reservoir is the source of recurrent ...

A New Method for Qualitative Multi-scale Analysis of Bacterial Biofilms on Filamentous Fungal Colonies Using Confocal and Electron Microscopy

Bacterial biofilms frequently form on fungal surfaces and can be involved in numerous bacterial-fungal interaction processes, such as metabolic cooperation, competition, or predation. The study of biofilms is important in many biological fields, including environmental science, food production, and medicine. However, few studies have focused on such bacterial biofilms, partially due to the difficulty of investigating them. Most of the methods for qualitative and quantitative biofilm analyses described in the literature are only suitable for biofilms forming on abiotic surfaces or on homogeneous and thin biotic surfaces, such as a monolayer of epithelial cells.
While laser scanning confocal microscopy (LSCM) is often used to analyze in situ and in vivo biofilms, this technology becomes very challenging when applied to bacterial biofilms on fungal hyphae, due to the thickness and the three dimensions of the hyphal networks. To overcome this shortcoming, we developed a protocol combining microscopy with a method to limit the accumulation of hyphal layers in fungal colonies. Using this method, we were able to investigate the development of bacterial biofilms on fungal hyphae at multiple scales using both LSCM and scanning electron microscopy (SEM). This report describes the protocol, including microorganism cultures, bacterial biofilm formation conditions, biofilm staining, and LSCM and SEM visualizations.

This protocol describes a new method to grow and qualitatively analyze bacterial biofilms on fungal hyphae by confocal and electron microscopy.

一种用于丝状真菌菌落细菌生物膜的定性多尺度分析的新方法利用共聚焦和电子显微镜

Bacterial biofilms frequently form on fungal surfaces and can be involved in numerous bacterial-fungal interaction processes, such as metabolic ...

A High-throughput Platform for the Screening of Salmonella spp./Shigella spp.

Fecal-oral transmission of acute gastroenteritis occurs from time to time, especially when people who handled food and water are infected by Salmonella spp./Shigella spp. The gold standard method for the detection of Salmonella spp./Shigella spp. is direct culture but this is labor-intensive and time-consuming. Here, we describe a high-throughput platform for Salmonella spp./Shigella spp. screening, using real-time polymerase chain reaction (PCR) combined with guided culture. There are two major stages: real-time PCR and the guided culture. For the first stage (real-time PCR), we explain each step of the method: sample collection, pre-enrichment, DNA extraction and real-time PCR. If the real-time PCR result is positive, then the second stage (guided culture) is performed: selective culture, biochemical identification and serological characterization. We also illustrate representative results generated from it. The protocol described here would be a valuable platform for the rapid, specific, sensitive and high-throughput screening of Salmonella spp./Shigella spp.

A High-throughput Platform for the Screening of Salmonella spp./Shigella spp.

Salmonella spp./Shigella spp. are common pathogens attributed to diarrhea. Here, we describe a high-throughput platform for the screening of Salmonella spp./Shigella spp. using real-time PCR combined with guided culture.

沙门氏菌筛选的高通量平台.

Fecal-oral transmission of acute gastroenteritis occurs from time to time, especially when people who handled food and water are infected by Salmonella ...

Arbovirus Infections As Screening Tools for the Identification of Viral Immunomodulators and Host Antiviral Factors

RNA interference- and genome editing-based screening platforms have been widely used to identify host cell factors that restrict virus replication. However, these screens are typically conducted in cells that are naturally permissive to the viral pathogen under study. Therefore, the robust replication of viruses in control conditions may limit the dynamic range of these screens. Furthermore, these screens may be unable to easily identify cellular defense pathways that restrict virus replication if the virus is well-adapted to the host and capable of countering antiviral defenses. In this article, we describe a new paradigm for exploring virus-host interactions through the use of screens that center on naturally abortive infections by arboviruses such as vesicular stomatitis virus (VSV). Despite the ability of VSV to replicate in a wide range of dipteran insect and mammalian hosts, VSV undergoes a post-entry, abortive infection in a variety of cell lines derived from lepidopteran insects, such as the gypsy moth (Lymantria dispar). However, these abortive VSV infections can be &#34;rescued&#34; when host cell antiviral defenses are compromised. We describe how VSV strains encoding convenient reporter genes and restrictive L. dispar cell lines can be paired to set-up screens to identify host factors involved in arbovirus restriction. Furthermore, we also show the utility of these screening tools in the identification of virally encoded factors that rescue VSV replication during coinfection or through ectopic expression, including those encoded by mammalian viruses. The natural restriction of VSV replication in L. dispar cells provides a high signal-to-noise ratio when screening for the conditions that promote VSV rescue, thus enabling the use of simplistic luminescence- and fluorescence-based assays to monitor the changes in VSV replication. These methodologies are valuable for understanding the interplay between host antiviral responses and viral immune evasion factors.

Here, we present the protocols to identify 1) virus-encoded immunomodulators that promote arbovirus replication and 2) eukaryotic host factors that restrict arbovirus replication. These fluorescence- and luminescence-based methods allow researchers to rapidly obtain quantitative readouts of arbovirus replication in simplistic assays with low signal-to-noise ratios.

虫媒病毒感染作为鉴定病毒免疫调节剂和宿主抗病毒因子的筛选工具

RNA interference- and genome editing-based screening platforms have been widely used to identify host cell factors that restrict virus replication. ...

Co-immunoprecipitation Assay for Studying Functional Interactions Between Receptors and Enzymes

Receptor-associated enzymes are the major mediators of cellular activation. These enzymes are regulated, at least in part, by physical interactions with cytoplasmic tails of the receptors. The interactions often occur through specific protein domains and result in activation of the enzymes. There are several methods to study interactions between proteins. While co-immunoprecipitation is commonly used to study domains that are required for protein-protein interactions, there are no assays that document the contribution of specific domains to activity of the recruited enzymes at the same time. Accordingly, the method described here combines co-immunoprecipitation and an on-bead enzymatic activity assay for simultaneous evaluation of interactions between proteins and associated enzymatic activation. The goal of this protocol is to identify the domains that are critical for physical interactions between a protein and enzyme and the domains that are obligatory for complete activation of the enzyme. The importance of this assay is demonstrated, as certain receptor protein domains contribute to the binding of the enzyme to the cytoplasmic tail of the receptor, while other domains are necessary to regulate the function of the same enzyme.

Here, we present a protocol for co-immunoprecipitation and an on-bead enzymatic activity assay to simultaneously study the contribution of specific protein domains of plasma membrane receptors to both enzyme recruitment and enzyme activity.

免疫沉淀法研究受体与酶的功能相互作用

Receptor-associated enzymes are the major mediators of cellular activation. These enzymes are regulated, at least in part, by physical interactions with ...

Spore Adsorption as a Nonrecombinant Display System for Enzymes and Antigens

The bacterial spore is a metabolically quiescent cell, formed by a series of protective layers surrounding a dehydrated cytoplasm. This peculiar structure makes the spore extremely stable and resistant and has suggested the use of the spore as a platform to display heterologous molecules. So far, a variety of antigens and enzymes have been displayed on spores of Bacillus subtilis and of a few other species, initially by a recombinant approach and, then, by a simple and efficient nonrecombinant method. The nonrecombinant display system is based on the direct adsorption of heterologous molecules on the spore surface, avoiding the construction of recombinant strains and the release of genetically modified bacteria in the environment. Adsorbed molecules are stabilized and protected by the interaction with spores, which limits the rapid degradation of antigens and the loss of enzyme activity at unfavorable conditions. Once utilized, spore-adsorbed enzymes can be collected easily with a minimal reduction of activity and reused for additional reaction rounds. In this paper is shown how to adsorb model molecules to purified spores of B. subtilis, how to evaluate the efficiency of adsorption, and how to collect used spores to recycle them for new reactions.

This protocol focuses on the use of bacterial spores as a &#34;live&#34; nanobiotechnological tool to adsorb heterologous molecules with various biological activities. The methods to measure the efficiency of adsorption are also shown.

作为酶和抗原的非重组显示系统的孢子吸附

The bacterial spore is a metabolically quiescent cell, formed by a series of protective layers surrounding a dehydrated cytoplasm. This peculiar structure ...

Bacterial Peptide Display for the Selection of Novel Biotinylating Enzymes

Biotin is an attractive post-translational modification of proteins that provides a powerful tag for the isolation and detection of protein. Enzymatic biotinylation by the E. coli biotin-protein ligase BirA is highly specific and allows for the biotinylation of target proteins in their native environment; however, the current usage of BirA mediated biotinylation requires the presence of a synthetic acceptor peptide (AP) in the target protein. Therefore, its application is limited to proteins that have been engineered to contain the AP. The purpose of the present protocol is to use the bacterial display of a peptide derived from an unmodified target protein to select for BirA variants that biotinylates the peptide. The system is based on a single plasmid that allows for the co-expression of BirA variants along with a scaffold for the peptide display on the bacterial surface. The protocol describes a detailed procedure for the incorporation of the target peptide into the display scaffold, creation of the BirA library, selection of active BirA variants and initial characterization of the isolated BirA variants. The method provides a highly effective selection system for the isolation of novel BirA variants that can be used for the further directed evolution of biotin-protein ligases that biotinylate a native protein in complex solutions.

Here we present a method to select for novel variants of the E. coli biotin-protein ligase BirA that biotinylates a specific target peptide. The protocol describes the construction of a plasmid for the bacterial display of the target peptide, generation of a BirA library, selection and characterization of BirA variants.

细菌肽显示用于选择新型生物仿生酶

Biotin is an attractive post-translational modification of proteins that provides a powerful tag for the isolation and detection of protein. Enzymatic ...

An Efficient Method for Directed Hepatocyte-Like Cell Induction from Human Embryonic Stem Cells

The potential functions of hepatocyte-like cells (HLCs) derived from human embryonic stem cells (hESCs) hold great promise for disease modeling and drug screening applications. Provided here is an efficient and reproducible method for differentiation of hESCs into functional HLCs. The establishment of an endoderm lineage is a key step in the differentiation to HLCs. By our method, we regulate the key signaling pathways by continuously supplementing Activin A and CHIR99021 during hESC differentiation into definitive endoderm (DE), followed by generation of hepatic progenitor cells, and finally HLCs with typical hepatocyte morphology in a stagewise method with completely defined reagents. The hESC-derived HLCs produced by this method express stage-specific markers (including albumin, HNF4&#945; nuclear receptor, and sodium taurocholate cotransporting polypeptide (NTCP)), and show special characteristics related to mature and functional hepatocytes (including indocyanine green staining, glycogen storage, hematoxylin-eosin staining and CYP3 activity), and can provide a platform for the development of HLC-based applications in the study of liver diseases.

This manuscript describes a detailed protocol for differentiation of human embryonic stem cells (hESCs) into functional hepatocyte-like cells (HLCs) by continuously supplementing Activin A and CHIR99021 during hESC differentiation into definitive endoderm (DE).

从人类胚胎干细胞中引导肝细胞样细胞诱导的有效方法

The potential functions of hepatocyte-like cells (HLCs) derived from human embryonic stem cells (hESCs) hold great promise for disease modeling and drug ...