Financial support from an Industrial Research Chair funded by FPInnovations and NSERC for a NSERC Discovery grant and from the NSERC Innovative Green Wood Fiber Products Network are acknowledged.

小心:触摸它们之前，请阅读所有化学品的材料安全数据表（MSDS）。许多在此工作中使用的化学品可能会导致严重的健康损害。使用个人防护，如实验室外套，手套和护目镜是必须的。不要忘记，安全是第一位的。在整个合成中使用的水是蒸馏水。 1.部分氧化纤维作为中间体的制备<ol><li>撕4克C-90软木纸浆片材切成小块的约2×2 平方厘米。 </li><li>浸泡撕裂纸浆片在水中至少一天。 </li><li>崩解使用机械粉碎机以实现几乎均匀分散的湿的纸浆。 </li><li>为了组装真空过滤，在布氏漏斗中确保一个尼龙过滤器，并放置在漏斗中的过滤器烧瓶中。然后，过滤器烧瓶连接到使用适当的管道真空泵。打开泵，并倒在funn崩解的纸浆解决方案埃尔到纸浆从液体中分离出来。 </li><li>测量湿纸浆（M 1）的重量，并计算出由纸浆的吸水量:M W，1 = M 1 - 4。 </li><li>高碘酸盐氧化剂溶液的制备<ol><li>对于SNCC / DAMC合成:分别在200- 男女，加入1ml水溶解2.64克高碘酸钠（的NaIO 4）和15.48氯化物克氯化钠（NaCl）。 </li><li>对于ENCC / DCC合成:分别在266- 男女，加入1ml水溶解5.33克高碘酸钠（的NaIO 4）和15.6氯化克氯化钠（NaCl）。 </li></ol></li><li>分别加入湿纸浆1.6准备的解决方案。确保的水的总量（由纸浆加加入水吸收）是等于200毫升SNCC和266毫升ENCC合成。 </li><li>覆盖烧杯用铝箔彻底防止高碘失活在RT以速度〜105转搅拌t的所需量，同时IME根据表1，实现了有利的醛含量。作为一个例子，以获得〜6.5毫摩尔/克醛，为96小时反应。 </li><li>当反应时间过去后，打开铝箔和（在ENCC / DCC合成的情况下）乙二醇加入1毫升（在SNCC / DAMC合成的情况下）或3 ml至该混合物并搅拌10分钟以终止氧化经淬火碘酸反应。 </li><li>收集通过真空过滤（根据1.4）的氧化纸浆，再分散它在500毫升水中，并搅拌它30分钟。重复此步骤，至少5次，以从高碘彻底清洁纸浆。 </li><li>在氧化的纸浆中的第 5 次水洗涤之后，纸浆从溶液通过真空过滤分离，将其存储在冷的（4℃）的地方。 </li></ol> 2. SNCC和DAMC的合成<ol><li>划分部分氧化的湿纸浆（M 1），在1.11得到，由四个:M 2 = M 1/4，并测量吸收水的重量:M W，2 = M 2 - 1。 </li><li>分散在纸浆（100 - 男女，2）克水在圆底烧瓶（总水含量= 100克）。 </li><li>放置在油浴中的圆底烧瓶中并加热，在80℃下的部分氧化的纸浆为6小时，同时轻轻地搅拌。 注意:如果纸浆被完全用高碘氧化（DS = 2）， 例如 ，通过在含有3.87克氯化钠（8.64毫摩尔）和65毫升的水，同时搅拌6的溶液1克纸浆1.85克的NaIO 4（8.65毫摩尔）反应天，这取决于水的加热条件和停留时间，二醛纤维素（DAC）的特性改变（ 表2）。 </li><li>冷却该溶液至室温。 </li><li>离心18,500 XG溶液10分钟。沉淀物是unfibrillated纤维素（级分1）。 </li><li>仔细分离上清液并称重（A）。 </li><li>加入1.7（A）G丙醇到，同时搅拌以沉淀SNCC在2.6得到的上清液。关于分离SNCC并添加丙醇细节是图1中可用。 </li><li>离心在3000 xg离心双相溶液10分钟，并分离所得凝胶状沉淀物（第二级分，SNCC）通过倾析，这是准备再分散和透析用于进一步纯化（部分4）和表征（部分5）。 </li><li>在2.8中得到的上清，加入3.5（A）G丙醇，得到白色沉淀物（第三级分，DAMC）。 </li><li>离心2.9的溶液在3000×g离心10分钟，并收集了凝胶状DAMC沉淀物（通过在一个单独的烧杯中倒出上清液）准备在水中再分散，通过透析纯化（在第4个可用的信息），并且其特征在于（第5节）。 </li></ol> 3. ENCC和DCC的合成<ol><li>在100毫升溶解制备0.5M的氢氧化钠（NaOH）的溶液中〜2克NaOH水，并保持它放在一边。这将在步骤3.7中使用。 </li><li>划分湿氧化纸浆，在1.11得到，由四个:M 3 = M 1/4，并测量吸收水的重量:M W，3 = 米3 - 1。 </li><li>另外，将添加2.93克氯化钠（NaCl）和1.41亚氯酸钠（次氯酸钠2） - （50 - 男女，3）毫升水搅拌溶解。 </li><li>暂停米3克在3.3中获得的溶液湿氧化处理的纸浆（含约1克干氧化纸浆）的。请注意，最终纸浆浓度为1g在50ml总可用水（游离和吸收水）。 </li><li>放置一个pH计在3.4的溶液中。 </li><li>添加1.41克过氧化氢 ​​（H 2 O 2）至步骤3.4中滴加该混合物。 </li><li>搅拌3.6在室温24小时的悬浮液在105转，同时通过逐渐加入在步骤3.1制得的0.5M氢氧化钠（NaOH）将pH保持〜5。 注:pH值开始减小，从反应开始后迅速〜15分钟，并且它应在5至少在反应的第一4小时保持恒定。为方便起见，它被认为该反应是在下午1点开始，将pH控制，直到下午5点，然​​后将反应是左的O / N和在上午将pH再增加到5月初。这么长的时间之后，pH值下降不会显著，表明大部分的转换得以实现。现在，几乎没有固体可在溶液中观察到的（大纤维被分解成纳米颗粒）。需要注意的是，如果反应在放置较长的时间，则结晶性部分可能会中断。 </li><li>划分从3.7 10分钟得到的成均等加权离心管中，离心以27,000 xg离心悬浮液中，并将上清液（ENCC + DCC）从微纤维的沉淀物分离。 </li><li>称重从3.8得到的上清液，并调用溶液质量（B）。 </li><li>慢慢加入0.16（B）G乙醇以3.9的溶液中，同时搅拌，形成白色沉淀物（第二级分，ENCC）。 </li><li>离心机的3.10在3000 xg离心10分钟的溶液中，并通过倾析分离所得凝胶状ENCC沉淀。 ENCC是准备在水中再分散，通过透析（在第4个可用的信息）进行纯化，并且其特征在于（第5部分）。 </li><li>以3.11得到的上清液中，添加乙醇等质量的溶液的质量，得到白色沉淀物（第三级分，DCC）。 </li><li>离心的3.12的溶液在3000×g离心10分钟，并分离凝胶状DCC沉淀准备在水中再分散，通过透析纯化（在第4个可用细节），并进行表征。 </li></ol> 4.透析过程净化SNCC，DAMC，ENCC或DCC <ol><li>剧烈搅拌1小时再分散在10ml水中2.8（SNCC）的任何步骤中得到的凝胶状沉淀物，2.10（DAMC），3.11（ENCC），或者3.13（DCC）。 </li><li>第广场在一个透析管e离散（分子量截留值= 12-14 kDa的，长度约30厘米，宽度约为4.5厘米），并通过夹紧固定的顶部和底部。 </li><li>放置在〜4升蒸馏水填充透析袋中，并搅拌24小时以喷射的盐。 </li><li>收集在冷的（4℃）处的容器和储存的透析溶液。 </li></ol> 5.后净化表征:固相和充电浓度测量<ol><li> 浓度测量 <ol><li>权衡的加权盘3毫升期望分散体（铝杯57毫米）。 </li><li>放置装有在烘箱（50℃）O / N分散体中的称量皿。 </li><li>称量干膜，并计算在分散纳米颗粒或聚合物的浓度: 浓度（重量/体积％）=干膜/ 3的100×质量，或 浓度（重量/重量％）=分散的干膜/质量100×质量</li></ol></li><li> 电导滴定 </st荣&gt; <ol><li> SNCC或DAMC确定醛含量的电导滴定 <ol><li>通过加入0.82毫升盐酸至25毫升水中，随后通过调节最终体积至100ml制备的0.1M盐酸（HCl）。 </li><li>单独地，通过将​​0.4克氢氧化钠至蒸馏水达到100 ml终溶液制备的NaOH的0.1M。 </li><li>继盐酸羟胺法24，所希望的分散体的公知的添加量的水所需量（ 例如和0.02克在50毫升H 2 O）。 </li><li>将pH调节至3.5使用稀盐酸（0.1M）。 </li><li>加入10 mL盐酸羟胺溶液（5％W / W）的分散液。 </li><li>监测pH值，并通过添加0.1M NaOH中直到pH变成3.5稳定保持在3.5。 </li><li>使用NaOH的消耗体积以中和从醛基和NH 2 OH·HCl的的反应中释放的H +测量醛concentra化（在反应过程中消耗的NaOH =摩尔产生的HCl的摩尔=上SNCC醛基摩尔）。 </li></ol></li><li> ENCC或DCC确定羧基含量的电导滴定 <ol><li>以下文献25中 ，添加所希望的分散体的足够量的有0.02克的固体140毫升蒸馏水。 </li><li>单独地，在蒸馏水中溶解0.117克NaCl达到100 ml终溶液制备20mM的NaCl洗涤。 2毫升20毫米氯化钠添加到5.2.2.1。 </li><li>降低pH值至约3用稀盐酸（0.1M）。 </li><li>通过以0.1毫升/分钟的增量加入标准氢氧化钠（NaOH，10毫摩尔）至pH〜11进行电导滴定。 </li><li>使用NaOH的消耗体积以中和电荷的基团（在图2中详细说明），测量表面电荷浓度（1摩尔消耗的碱的等于1摩尔羧基的粒子表面上）。 </li></ol></li></ol></li></ol>

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The authors have nothing to disclose.

以下在此视觉本文所讨论的化学，高度稳定的基于纤维素的纳米颗粒的具有可调电荷轴承结晶和非结晶相（毛状纳米晶纤维素）的频谱产生。取决于碘酸氧化时间，如表1所示，各种产品，得到:氧化纤维（级分1），SNCC（级分2），和DAMC（馏分3），其每个提供独特的性能，如所定义的大小，形态，结晶度，和醛含量。在各种带负电荷的物质，即馏分1（羧化的纸浆纤维），级分2（ENCC）?...

纤维素，如在世界上最丰富的生物聚合物，已被最近担任一个关键原料，得到命名纳米晶纤维素晶体纳米颗粒（NCC，也被称为纤维素纳米晶体的CNC）1。理解NCC合成的机理，需要探索纤维素纤维的结构。纤维素是直链和包含聚β-（1,4）-D-葡萄糖残基2多分散聚合物。在各单体的糖环通过糖苷氧连接形成的（1-1.5）链×10 4个吡喃葡萄糖单元2,3，引入交替结晶份和无序的，无定形的区域，首先通过Nageli和施文德纳2,4报道。取决于来源，纤维素的结晶部分可以采取多种多晶型5。 如果纤维素纤维是用强酸处理，如硫酸，非晶相可以是完全水解AWAy以扰乱聚合物并产生取决于来源各种长宽比的晶体颗粒（ 例如 ，宽度的木材和棉花产量的90％以上的结晶纳米棒〜5-10纳米，长度〜100-300纳米，而tunicin，细菌，和藻类产生5-60纳米宽，100纳米至微米几个长NCC的）6。读者可参考在这些纳米材料2,5,7-16的科学和工程方面提供了大量的文学作品。尽管这些纳米颗粒的许多有趣的性质，它们的胶体稳定性一直在高盐浓度和高/低pH值的问题，由于其相对低的表面电荷量（小于1毫摩尔/克）17。 代替强酸水解，纤维素纤维可以用氧化剂（高碘）进行处理，在脱水-D-吡喃葡萄糖残基裂解的C 2 -C 3键以形成2,3-二醛单元无显著副反应18,19。这些部分氧化的纤维可以被用来作为一种有价值的中间体材料以产生仅仅使用化学反应的纳米颗粒轴承非晶和结晶区域（毛状纳米晶纤维素），无需任何机械剪切或超声处理20。当部分氧化度DS &lt;2，加热氧化中的产品，即纤维状纤维素，水分散性二醛纤维素纳米晶须称为空间稳定的纳米晶纤维素（SNCC）三批纤维的结果，并溶解二醛改性纤维素（DAMC），其可以分离通过在共溶剂加成和精确控制间歇离心21。 对所述部分氧化的纤维受控氯酸盐氧化转换几乎所有的醛基至羧基单元，它可以为每克微晶纤维素引入高达7毫摩尔COOH基团视醛含量18 </suP&gt;，作为稳定剂。这些纳米颗粒被称为electrosterically稳定纳米晶纤维素（ENCC）。此外，已经证实，带电毛发状凸出链软层上ENCC 17存在。这种材料已被用来作为一种高效吸附剂来清除重金属离子22。电荷这些纳米颗粒能够通过控制高碘反应时间23被精确地控制。 尽管纤维素的已知氧化还原反应，生产SNCC和ENCC的从未报道过的任何其他研究小组最可能是由于在分离的挑战。我们已经能够成功地合成和通过精确设计的反应和分离步骤分离纳米产品的各种馏分。这种视觉文章完整详细演示了如何重现性准备和表征上述新型纳米晶须轴承非晶和晶体部分期从木质纤维。本教程可能是在软质材料，生物和医药科学，纳米技术和纳米光子学，环境科学与工程和物理学领域活跃的研究人员的资产。

<table border="0" cellpadding="0" cellspacing="0" width="947">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Q-90 softwood pulp</td>
			<td style="width:149px;">FPInnovations</td>
			<td style="width:213px;">-</td>
			<td style="width:369px;">-</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Sodium periodate</td>
			<td style="width:149px;">Sigma-Aldrich</td>
			<td style="width:213px;">S1878-500G/CAS7790-28-5</td>
			<td style="width:369px;">Light sensitive, Strong oxidizer, must be kept away from flammable materials</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sodium chloride</td>
			<td style="width:149px;">ACP Chemicals</td>
			<td style="width:213px;">S2830-3kg/7647-14-5</td>
			<td style="width:369px;">-</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">2-Propanol</td>
			<td style="width:149px;">Fisher</td>
			<td style="width:213px;">L-13597/67-63-0</td>
			<td style="width:369px;">Flammable</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ethylene glycol</td>
			<td style="width:149px;">Sigma-Aldrich</td>
			<td style="width:213px;">102466-1L/107-21-1</td>
			<td style="width:369px;">-</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sodium hydroxide</td>
			<td style="width:149px;">Fisher</td>
			<td style="width:213px;">L-19234/1310-73-2</td>
			<td style="width:369px;">Strong base, causes serious health effects</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Sodium chlorite</td>
			<td style="width:149px;">Sigma-Aldrich</td>
			<td style="width:213px;">71388-250G/7758-19-2</td>
			<td style="width:369px;">Reactive with reducing agents and combustible materials</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Hydrogen peroxide</td>
			<td style="width:149px;">Fisher</td>
			<td style="width:213px;">H325-500/7722-84-1</td>
			<td style="width:369px;">Corrosive and oxidizing agent, keep in a cool and dark place</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ethanol</td>
			<td style="width:149px;">Commercial alcohols</td>
			<td style="width:213px;">P016EAAN</td>
			<td style="width:369px;">Flammable</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Hydrochloric acid</td>
			<td style="width:149px;">ACP Chemicals</td>
			<td style="width:213px;">H-6100-500mL/7647-01-0</td>
			<td style="width:369px;">Strong acid, causes serious health effects</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Hydroxylamine hydrochloride</td>
			<td style="width:149px;">Sigma-Aldrich</td>
			<td style="width:213px;">159417-100G/5470-11-1</td>
			<td style="width:369px;">Unstable at high temperature and humidity, mutagenic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Centrifuge</td>
			<td style="width:149px;">Beckman Coulter</td>
			<td style="width:213px;">J2</td>
			<td>High rotary speed</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Fixed angle rotor</td>
			<td style="width:149px;">Beckman Coulter</td>
			<td style="width:213px;">JA-25.50</td>
			<td>Tighten the lid carefully</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:216px;">Dialysis tubing</td>
			<td style="width:149px;">Spectrum Labs</td>
			<td style="width:213px;">Spectra (Part No. 132676)</td>
			<td>Cutoff Mw = 12-14 kD, Length ~ 30 cm, width ~ 4.5 cm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Aluminum cup</td>
			<td style="width:149px;">VWR</td>
			<td style="width:213px;">611-1371</td>
			<td>57 mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Titrator</td>
			<td style="width:149px;">Metrohm</td>
			<td style="width:213px;">836 Titrando</td>
			<td>-</td>
		</tr>
	</tbody>
</table>

highly stable, functional hairy nanoparticles and biopolymers from wood fibers: towards sustainable nanotechnology

纳米粒子，如纳米技术和纳米医学的关键材料之一，在过去十年中取得了显著的重要性。虽然基于金属纳米粒子合成和环境相关的麻烦，纤维素引入了纳米粒子合成一个绿色，可持续的替代。这里，我们提出的化学合成和分离程序以基于木材纤维毛的纳米颗粒（轴承非晶和结晶区域）和生物聚合物的新类。通过软木浆的高碘酸盐氧化，纤维素的葡萄糖环的C 2 -C 3键被打开以形成2,3-二醛基。部分氧化的纤维进一步加热（ 例如 ，T = 80℃）的结果在三个产品，即纤维状氧化纤维素，空间稳定的纳米晶纤维素（SNCC），并溶解二醛改性纤维素（DAMC），这是公通过间歇离心分离和共溶剂加成。部分氧化的纤维（不加热）被用作一个高反应性的中间产物以用亚反应转换几乎所有醛的羧基。共溶剂沉淀和离心导致electrosterically稳定纳米晶纤维素（ENCC）和二羧基化纤维素（DCC）。 SNCC因此表面电荷ENCC（羧基含量）被精确地通过控制碘酸氧化反应时间，从而导致高度稳定的纳米颗粒的轴承每克的纳米颗粒（ 如超过700毫摩尔的官能团，受控的醛的含量比常规NCC轴承&lt;&lt; 1毫摩尔官能团/克）。原子力显微镜（AFM），透射电子显微镜（TEM）和扫描电子显微镜（SEM）证明了棒状的形态。电导滴定，傅立叶变换红外光谱（FTIR），核磁共振（NMR），动态光散射（DLS），电动 - S的ONIC振幅（ESA）和声衰减谱棚光对这些纳米材料的优异性能。

纸浆的高碘和绿泥石氧化期间每个部分的质量部分和电荷含量取决于反应时间（ 见表1）。此外，DAC分子量取决于加热条件和停留时间（ 见表2）。一旦SNCC和DAMC制成，它们通过添加丙醇（ 图1）中沉淀出来。为了测量ENCC的电荷内容，电导滴定进行（ 图2）。 NCC和ENCC胶体行为由离子强度和pH的影响。的大小和NCC和ENCC与氯化?...

Watch this Scientific Journal Video about Highly Stable, Functional Hairy Nanoparticles and Biopolymers from Wood Fibers: Towards Sustainable Nanotechnology at JoVE.com

Highly Stable, Functional Hairy Nanoparticles and Biopolymers from Wood Fibers: Towards Sustainable Nanotechnology

Synthesis schemes to prepare highly stable wood fiber-based hairy nanoparticles and functional cellulose-based biopolymers have been detailed.

高稳定性，功能性毛纳米粒子和木纤维生物聚合物:迈向可持续纳米技术

Nanoparticles, as one of the key materials in nanotechnology and nanomedicine, have gained significant importance during the past decade. While ...

highly-stable-functional-hairy-nanoparticles-biopolymers-from-wood

Research

JoVE Journal

Chemistry

11.9K 次观看.  McGill University. Synthesis schemes to prepare highly stable wood fiber-based hairy nanoparticles and functional cellulose-based biopolymers have been detailed. 

视频: Highly Stable, Functional Hairy Nanoparticles and Biopolymers from Wood Fibers: Towards Sustainable Nanotechnology

Formation of Ordered Biomolecular Structures by the Self-assembly of Short Peptides

In nature, complex functional structures are formed by the self-assembly of biomolecules under mild conditions. Understanding the forces that control self-assembly and mimicking this process in vitro will bring about major advances in the areas of materials science and nanotechnology. Among the available biological building blocks, peptides have several advantages as they present substantial diversity, their synthesis in large scale is straightforward, and they can easily be modified with biological and chemical entities1,2. Several classes of designed peptides such as cyclic peptides, amphiphile peptides and peptide-conjugates self-assemble into ordered structures in solution. Homoaromatic dipeptides, are a class of short self-assembled peptides that contain all the molecular information needed to form ordered structures such as nanotubes, spheres and fibrils3-8. A large variety of these peptides is commercially available.
This paper presents a procedure that leads to the formation of ordered structures by the self-assembly of homoaromatic peptides. The protocol requires only commercial reagents and basic laboratory equipment. In addition, the paper describes some of the methods available for the characterization of peptide-based assemblies. These methods include electron and atomic force microscopy and Fourier-Transform Infrared Spectroscopy (FT-IR). Moreover, the manuscript demonstrates the blending of peptides (coassembly) and the formation of a &#34;beads on a string&#34;-like structure by this process.9 The protocols presented here can be adapted to other classes of peptides or biological building blocks and can potentially lead to the discovery of new peptide-based structures and to better control of their assembly.

This paper describes the formation of highly ordered peptide-based structures by the spontaneous process of self-assembly. The method utilizes commercially available peptides and common lab equipment. This technique can be applied to a large variety of peptides and may lead to the discovery of new peptide-based assemblies.

生物分子有序结构由短肽的自组装形成

In nature, complex functional structures are formed by the self-assembly of biomolecules under mild conditions. Understanding the forces that control ...

科研

化学

Towards Biomimicking Wood: Fabricated Free-standing Films of Nanocellulose, Lignin, and a Synthetic Polycation

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and lignin. Layer-by-layer (LbL) assembly process which relies on the assembly of oppositely charged molecules from aqueous solutions was used to build a freestanding composite film of isolated wood polymers of lignin and oxidized nanofibril cellulose (NFC). To facilitate the assembly of these negatively charged polymers, a positively charged polyelectrolyte, poly(diallyldimethylammomium chloride) (PDDA), was used as a linking layer to create this simplified model cell wall. The layered adsorption process was studied quantitatively using quartz crystal microbalance with dissipation monitoring (QCM-D) and ellipsometry. The results showed that layer mass/thickness per adsorbed layer increased as a function of total number of layers. The surface coverage of the adsorbed layers was studied with atomic force microscopy (AFM). Complete coverage of the surface with lignin in all the deposition cycles was found for the system, however, surface coverage by NFC increased with the number of layers. The adsorption process was carried out for 250 cycles (500 bilayers) on a cellulose acetate (CA) substrate. Transparent free-standing LBL assembled nanocomposite films were obtained when the CA substrate was later dissolved in acetone. Scanning electron microscopy (SEM) of the fractured cross-sections showed a lamellar structure, and the thickness per adsorption cycle (PDDA-Lignin-PDDA-NC) was estimated to be 17 nm for two different lignin types used in the study. The data indicates a film with highly controlled architecture where nanocellulose and lignin are spatially deposited on the nanoscale (a polymer-polymer nanocomposites), similar to what is observed in the native cell wall.

The objective of this research was to form synthetic plant cell wall tissue using layer-by-layer assembly of nanocellulose fibrils and isolated lignin assembled from dilute aqueous suspensions.&#160; Surface measurement techniques of quartz crystal microbalance and atomic force microscopy were used to monitor the formation of the polymer-polymer nanocomposite material.

朝仿生学木:纳米纤维素，木质素的装配式自由站立电影和合成聚阳离子

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and ...

Folding and Characterization of a Bio-responsive Robot from DNA Origami

The DNA nanorobot is a hollow hexagonal nanometric device, designed to open in response to specific stimuli and present cargo sequestered inside. Both stimuli and cargo can be tailored according to specific needs. Here we describe the DNA nanorobot fabrication protocol, with the use of the DNA origami technique. The procedure initiates by mixing short single-strand DNA staples into a stock mixture which is then added to a long, circular, single-strand DNA scaffold in presence of a folding buffer. A standard thermo cycler is programmed to gradually lower the mixing reaction temperature to facilitate the staples-to-scaffold annealing, which is the guiding force behind the folding of the nanorobot. Once the 60 hr folding reaction is complete, excess staples are discarded using a centrifugal filter, followed by visualization via agarose-gel electrophoresis (AGE). Finally, successful fabrication of the nanorobot is verified by transmission electron microscopy (TEM), with the use of uranyl-formate as negative stain.

DNA origami is a powerful method for fabricating precise nanoscale objects by programming the self-assembly of DNA molecules. Here we describe a protocol for the folding of a bio-responsive robot from DNA origami, its purification and negative staining for transmission electron microscopic imaging (TEM).

折叠的DNA折纸一个生物反应机器人与表征

The DNA nanorobot is a hollow hexagonal nanometric device, designed to open in response to specific stimuli and present cargo sequestered inside. Both ...

From Constructs to Crystals &#8211; Towards Structure Determination of &#946;-barrel Outer Membrane Proteins

Membrane proteins serve important functions in cells such as nutrient transport, motility, signaling, survival and virulence, yet constitute only ~1% percent of known structures. There are two types of membrane proteins, &#945;-helical and &#946;-barrel. While &#945;-helical membrane proteins can be found in nearly all cellular membranes, &#946;-barrel membrane proteins can only be found in the outer membranes of mitochondria, chloroplasts, and Gram-negative bacteria. One common bottleneck in structural studies of membrane proteins in general is getting enough pure sample for analysis. In hopes of assisting those interested in solving the structure of their favorite &#946;-barrel outer membrane protein (OMP), general protocols are presented for the production of target &#946;-barrel OMPs at levels useful for structure determination by either X-ray crystallography and/or NMR spectroscopy. Here, we outline construct design for both native expression and for expression into inclusion bodies, purification using an affinity tag, and crystallization using detergent screening, bicelle, and lipidic cubic phase techniques. These protocols have been tested and found to work for most OMPs from Gram-negative bacteria; however, there are some targets, particularly for mitochondria and chloroplasts that may require other methods for expression and purification. As such, the methods here should be applicable for most projects that involve OMPs from Gram-negative bacteria, yet the expression levels and amount of purified sample will vary depending on the target OMP.

&#946;-barrel outer membrane proteins (OMPs) serve many functions within the outer membranes of Gram-negative bacteria, mitochondria, and chloroplasts. Here, we hope to alleviate a known bottleneck in structural studies by presenting protocols for the production of &#946;-barrel OMPs in sufficient quantities for structure determination by X-ray crystallography or NMR spectroscopy.

从构造到晶体 - 迈向β桶外膜蛋白的结构解析

Membrane proteins serve important functions in cells such as nutrient transport, motility, signaling, survival and virulence, yet constitute only ~1% ...

Layer-by-layer Synthesis and Transfer of Freestanding Conjugated Microporous Polymer Nanomembranes

CMP as large surface area materials have attracted growing interest recently, due to their high variability in the incorporation of functional groups in combination with their outstanding thermal and chemical stability, and low densities. However, their insoluble nature causes problems in their processing since usually applied techniques such as spin coating are not available. Especially for membrane applications, where the processing of CMP as thin films is desirable, the processing problems have hindered their commercial application.
Here we describe the interfacial synthesis of CMP thin films on functionalized substrates via molecular layer-by-layer (l-b-l) synthesis. This process allows the preparation of films with desired thickness and composition and even desired composition gradients.
The use of sacrificial supports allows the preparation of freestanding membranes by dissolution of the support after the synthesis. To handle such ultra-thin freestanding membranes the protection with sacrificial coatings showed great promise, to avoid rupture of the nanomembranes. To transfer the nanomembranes to the desired substrate, the coated membranes are upfloated at the air-liquid interface and then transferred via dip coating.

In this paper we describe the interfacial synthesis of conjugated microporous polymers (CMP) on sacrificial substrates, and the dissolution of the substrate for the preparation of freestanding CMP nanomembranes. In addition, we will describe how the fragile nanomembranes can be transferred to other substrates.

层 - 层的合成和独立式共轭微孔聚合物纳米薄膜的转移

CMP as large surface area materials have attracted growing interest recently, due to their high variability in the incorporation of functional groups in ...

A Simple Method for the Size Controlled Synthesis of Stable Oligomeric Clusters of Gold Nanoparticles under Ambient Conditions

Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like oligomeric clusters of these yellow nanoparticles of narrow size distribution are synthesized under ambient conditions via two methods. The delay-time method controls the number of subunits in the oligoclusters by varying the time between the addition of HAuCl4 to alkaline solution and the subsequent addition of reducing agent, NaSCN. The yellow oligoclusters produced range in size from ~3 to ~25 nm. This size range can be further extended by an add-on method utilizing hydroxylated gold chloride (Na+[Au(OH4-x)Clx]-) to auto-catalytically increase the number of subunits in the as-synthesized oligocluster nanoparticles, providing a total range of 3 nm to 70 nm. The crude oligocluster preparations display narrow size distributions and do not require further fractionation for most purposes. The oligoclusters formed can be concentrated &#62;300 fold without aggregation and the crude reaction mixtures remain stable for weeks without further processing. Because these oligomeric clusters can be concentrated before derivatization they allow expensive derivatizing agents to be used economically. In addition, we present two models by which predictions of particle size can be made with great accuracy.

We describe a simple method for producing highly stable oligomeric clusters of gold nanoparticles via the reduction of chloroauric acid (HAuCl4) with sodium thiocyanate (NaSCN). The oligoclusters have a narrow size distribution and can be produced with a wide range of sizes and surface coats.

根据环境条件的金纳米粒子的稳定低聚簇的大小控制合成的一种简便方法

Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like ...

Photochemical Oxidative Growth of Iridium Oxide Nanoparticles on CdSe@CdS Nanorods

We demonstrate a procedure for the photochemical oxidative growth of iridium oxide catalysts on the surface of seeded cadmium selenide-cadmium sulfide (CdSe@CdS) nanorod photocatalysts. Seeded rods are grown using a colloidal hot-injection method and then moved to an aqueous medium by ligand exchange. CdSe@CdS nanorods, an iridium precursor and other salts are mixed and illuminated. The deposition process is initiated by absorption of photons by the semiconductor particle, which results with formation of charge carriers that are used to promote redox reactions. To insure photochemical oxidative growth we used an electron scavenger. The photogenerated holes oxidize the iridium precursor, apparently in a mediated oxidative pathway. This results in the growth of high quality crystalline iridium oxide particles, ranging from 0.5 nm to about 3 nm, along the surface of the rod. Iridium oxide grown on CdSe@CdS heterostructures was studied by a variety of characterization methods, in order to evaluate its characteristics and quality. We explored means for control over particle size, crystallinity, deposition location on the CdS rod, and composition. Illumination time and excitation wavelength were found to be key parameters for such control. The influence of different growth conditions and the characterization of these heterostructures are described alongside a detailed description of their synthesis. Of significance is the fact that the addition of iridium oxide afforded the rods astounding photochemical stability under prolonged illumination in pure water (alleviating the requirement for hole scavengers).

A protocol for the photochemical oxidative growth of small crystalline iridium oxide nanoparticles on the surface of CdSe@CdS seeded rod nanoparticles is presented.

铱氧化物纳米颗粒对硒化镉硫化镉@纳米棒光化学氧化增长

We demonstrate a procedure for the photochemical oxidative growth of iridium oxide catalysts on the surface of seeded cadmium selenide-cadmium sulfide ...

Green and Low-cost Production of Thermally Stable and Carboxylated Cellulose Nanocrystals and Nanofibrils Using Highly Recyclable Dicarboxylic Acids

Here we demonstrate potentially low cost and green productions of high thermally stable and carboxylated cellulose nanocrystals (CNCs) and nanofibrils (CNF) from bleached eucalyptus pulp (BEP) and unbleached mixed hardwood kraft pulp (UMHP) fibers using highly recyclable dicarboxylic solid acids. Typical operating conditions were acid concentrations of 50 - 70 wt% at 100 &#176;C for 60 min and 120 &#176;C (no boiling at atmospheric pressure) for 120 min, for BEP and UMHP, respectively. The resultant CNCs have a higher thermal degradation temperature than their corresponding feed fibers and carboxylic acid group content from 0.2 - 0.4 mmol/g. The low strength (high pKa of 1.0 - 3.0) of organic acids also resulted in CNCs with both longer lengths of approximately 239 - 336 nm and higher crystallinity than CNCs produced using mineral acids. Cellulose loss to sugar was minimal. Fibrous cellulosic solid residue (FCSR) from the dicarboxylic acid hydrolysis was used to produce carboxylated CNFs through subsequent mechanical fibrillation with low energy input.

Here we demonstrate a novel method for green and sustainable productions of highly thermally stable and carboxylated cellulose nanocrystals (CNC) and nanofibrils (CNF) using highly recyclable solid dicarboxylic acids.

热稳定和羧基化纤维素纳米晶和纳米原纤维使用高度可回收的二元羧酸绿色和低成本生产

Here we demonstrate potentially low cost and green productions of high thermally stable and carboxylated cellulose nanocrystals (CNCs) and nanofibrils ...

Microfluidic Dry-spinning and Characterization of Regenerated Silk Fibroin Fibers

The protocol demonstrates a method for mimicking the spinning process of silkworm. In the native spinning process, the contracting spinning duct enables the silk proteins to be compact and ordered by shearing and elongation forces. Here, a biomimetic microfluidic channel was designed to mimic the specific geometry of the spinning duct of the silkworm. Regenerated silk fibroin (RSF) spinning doped with high concentration, was extruded through the microchannel to dry-spin fibers at ambient temperature and pressure. In the post-treated process, the as-spun fibers were drawn and stored in ethanol aqueous solution. Synchrotron radiation wide-angle X-ray diffraction (SR-WAXD) technology was used to investigate the microstructure of single RSF fibers, which were fixed to a sample holder with the RSF fiber axis normal to the microbeam of the X-ray. The crystallinity, crystallite size, and crystalline orientation of the fiber were calculated from the WAXD data. The diffraction arcs near the equator of the two-dimensional WAXD pattern indicate that the post-treated RSF fiber has a high orientation degree.

A protocol for the microfluidic spinning and microstructure characterization of regenerated silk fibroin monofilament is presented.

微流控干纺及再生丝素纤维的表征

The protocol demonstrates a method for mimicking the spinning process of silkworm. In the native spinning process, the contracting spinning duct enables ...

Stable DNA Motifs, 1D and 2D Nanostructures Constructed from Small Circular DNA Molecules

This article presents a detailed protocol for synthesis of small circular DNA molecules, annealing of circular DNA motifs, and construction of 1D and 2D DNA nanostructures. Over decades, the rapid development of DNA nanotechnology is attributed to the use of linear DNAs as the source materials. For example, the DAO (double crossover, antiparallel, odd half-turns) tile is well-known as a building block for construction of 2D DNA lattices; the core structure of DAO is made from two linear single-stranded (ss) oligonucleotides, like two ropes making a right hand granny&#160;knot. Herein, a new type of DNA tiles called cDAO (coupled DAO) are built using a small circular ss-DNA of c64nt or c84nt (circular 64 or 84 nucleotides) as the scaffold strand and several linear ss-DNAs as the staple strands. Perfect 1D and 2D nanostructures are assembled from cDAO tiles: infinite nanowires, nanospirals, nanotubes, nanoribbons; and finite nano-rectangles. Detailed protocols are described: 1) preparation by T4 ligase and purification by denaturing PAGE (polyacrylamide gel electrophoresis) of small circular oligonucleotides, 2) annealing of stable circular tiles, followed by native PAGE analysis, 3) assembling of infinite 1D nanowires, nanorings, nanospirals, infinite 2D lattices of nanotubes and nanoribbons, and finite 2D nano-rectangles, followed by AFM (Atomic Force Microscopy) imaging. The method is simple, robust, and affordable for most labs.

This article presents a detailed protocol for T4 ligation and denaturing PAGE purification of small circular DNA molecules, annealing and native PAGE analysis of circular tiles, assembling and AFM imaging of 1D and 2D DNA nanostructures, as well as agarose gel electrophoresis and centrifugation purification of finite DNA nanostructures.

由小圆形 DNA 分子构建的稳定 DNA 分子、一维和二维纳米结构

This article presents a detailed protocol for synthesis of small circular DNA molecules, annealing of circular DNA motifs, and construction of 1D and 2D ...