Verification of Thermodynamic Theories of Strain-induced Polymer Crystallization

We studied the crystallization of nearly “homogeneous” polyethylene glycol (PEG) networks prepared by end-crosslinking of tetra-armed PEG. The influence of stretching ratio and strand length on the melting and crystallization...

The importance of being cross-linked for the bacterial cell wall

The bacterial cell wall is primarily composed of a mesh of stiff glycan strands cross-linked by peptide bridges and is essential for safeguarding the cell. The structure of the cell wall has to be stiff enough to bear the high turgor pressure and sufficiently tough to ensure protection against failure. Here we explore the role of various design features of the cell in enhancing the toughness of the cell wall. We explain how the glycan strand length distribution and the degree of cross-linking can play a vital role in ensuring that the cell wall offers sufficient resistance to propagation of cracks. We suggest a possible mechanism by which peptide bond hydrolysis can also help mitigate this risk of failure. We also study the reinforcing effect of MreB on the cell wall and conclude that the cross-linked structure of the cell wall plays the more important role in safeguarding against mechanical failure due to cracking.

Exciton dynamics in DNA oligomers studied by broadband deep-UV transient absorption spectroscopy

We report broadband transient absorption measurements of adenine strands in the deep-UV (250-370 nm). By varying the strand length we resolve the interplay between inter-base stacking and exciton formation and dynamics in DNA oligomers.

Conformational structure-dependent molecular recognition of two aptamers for tetracycline

Base sequence, strand length, and number of recognition sites codetermine conformational structure and performance of aptamers for tetracycline recognition.

Mechanical properties of polymer gels with bimodal distribution in strand length

ABSTRACTThe understanding of the physical properties of hydrogels has been controversial because hydrogels inherently have a substantial amount of heterogeneities in their structures. In this study, we focused on one of the simplest heterogeneities, heterogeneous distribution of strand length, and investigated its influence on physical properties. We prepared Tetra-PEG gels with bimodal distribution in strand length (Tetra-PEG bimodal gels) by combining Tetra-PEG prepolymers with different molecular weights and measured the physical properties including elastic modulus and ultimate deformation ratio. The physical properties of Tetra-PEG bimodal gels were well described by the models for conventional Tetra-PEG gels with the average polymerization degrees between cross-links. We conclude that the mechanical properties of hydrogels that have heterogeneous distribution in strand length can be predicted from those of hydrogels with the average strand length in the range tested in this study.