Relationship between molecular structure, gelation behaviour and gel properties of Fmoc-dipeptides
Relationship between molecular structure, gelation behaviour and gel properties of Fmoc-dipeptides
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DOI：
10.1039/b921863g
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发表时间：
2010-01-01
期刊：
影响因子：
3.4
通讯作者：
Frith, William J.
中科院分区：
文献类型：
--
作者：
Adams, Dave J.;Mullen, Leanne M.;Frith, William J.
我们研究了分子结构对一系列fmoc -二肽凝胶行为的影响。凝胶化是用葡萄糖醛酸- δ内酯触发的，它可以控制地降低pH值，使凝胶性能随时间的推移而保持不变。这是在凝胶强度的发展方面使用流变学观察到的。总的来说，我们发现形成稳定凝胶的能力是由fmoc -二肽的总体疏水性决定的。对于浓度为14.62 mM的fmoc -二肽，疏水性较弱的凝胶形成了协同作用（log P < 2.8）。在中等疏水性（2.8 < log P < 5.5）下，pH为4时形成自支撑凝胶。然而，不同的二肽以不同的速度组装，可能是由于不同的pK(a)（由二肽的不同疏水性引起）和形成不同硬度的凝胶。对两种fmoc二肽（FmocLG和FmocFG）进行了更详细的研究。研究了凝胶模量对浓度的依赖关系，发现其近似为1.4幂定律，这对于此类材料来说是非常低的。凝胶在经受大变形压缩试验时的行为也不寻常。在足够高的压缩率下，凝胶反应本质上是脆性的，显示出一个初始弹性区域，其杨氏模量与测量的剪切模量一致，并且在3-5%的应变下发生破坏。然而，在较低的压缩率下，水从凝胶中表达出来，导致其不可逆的压实。这种行为与凝胶是由刚性棒状结构网络组成的观点是一致的，如果变形超过其弹性极限，将无法恢复其原始形状。
We have investigated the influence of molecular structure on the gelation behaviour of a range of Fmoc-dipeptides. Gelation is triggered using glucono-delta-lactone, which controllably lowers the pH, allowing the gel properties to be followed with time. This was observed in terms of the development of the gel strength using rheology. In general, we find that the ability to form a stable gel is determined by the overall hydrophobicity of the Fmoc-dipeptide. For the Fmoc-dipeptides investigated at concentrations of 14.62 mM, gels that undergo syneresis are formed for those that are less hydrophobic (log P < 2.8). At intermediate hydrophobicities (2.8 < log P < 5.5), self-supporting gels are formed at pH 4. However, the different dipeptides assemble at different rates, possibly due to differences in pK(a) (arising from the different hydrophobicities of the dipeptides) and form gels of a variety of stiffnesses. Two Fmoc-dipeptides (FmocLG and FmocFG) were studied in more detail. The dependence of the gel modulus on concentration was investigated and found to approximate a 1.4 power law, which is unusually low for such materials. The behaviour of the gels when subjected to large deformation compression testing was also unusual. At sufficiently high compression rates, the gel response is brittle in nature, showing an initial elastic region with a Young's modulus consistent with the measured shear moduli and failure occurring at 3-5% strain. However, at lower compression rates, water is expressed from the gel, resulting in its irreversible compaction. Such behaviour is consistent with the idea that the gels are composed of networks of rigid rod-like structures, which, if deformed beyond their elastic limit will not recover their original form.