Self-Assembly of Peptide-Conjugated Forklike Mesogens at Aqueous/Liquid Crystalline Interfaces: Molecular Design for Ordering Transition Induced by Specific Binding of Biomolecules.

Self-assembly of functional liquid crystals provides a powerful approach to the development of stimuli-responsive materials and interfaces. Here, we have designed and synthesized bioconjugated amphiphilic dendritic mesogens containing arginine-glycine-aspartic acid (RGD) peptide sequence to develop new biofunctional aqueous/liquid crystalline interfaces. We have found that the RGD peptide-conjugated forklike mesogens induce the homeotropic alignment of liquid crystals at the aqueous interfaces, leading to distinct optical changes caused by the specific binding of the target proteins. In contrast, no response to the target protein is observed for the interfaces prepared with the RGD peptide-conjugated single mesogen. Molecular insights into the orientation and stimuli-responsiveness of the bioconjugated mesogens at the interfaces are obtained based on measurements of the Langmuir films and self-assembled properties of these molecules. These results demonstrate that the number of rodlike cores of the bioconjugated mesogens affects the monolayer structures formed at the aqueous interface as well as the liquid crystalline properties. We propose a new molecular design of bioconjugated mesogens to couple biomolecular interactions at the aqueous interfaces with the ordering transition of the liquid crystals. These materials have the potential to tailor the responsiveness of liquid crystalline interfaces for biomolecular sensing.

Efficient extraction and preservation of thermotolerant phycocyanins from red alga Cyanidioschyzon merolae.

C-Phycocyanin (PC) is a protein used commercially as a natural blue pigment produced by cyanobacteria, cryptophytes, and rhodophytes. Although it is industrially synthesized from the cyanobacterium Arthrospira platensis, PC requires high levels of energy for its extraction, which involves freezing of cells. However, as a protein, PC is easily denatured at extreme temperatures. In this study, we extracted PC from the red alga Cyanidioschyzon merolae, denoted as CmPC, and found that this protein was tolerant to high temperatures and acidic pH. CmPC was extracted by suspending cells in water mixed with various salts and organic acids without freeze-drying or freeze-thaw. The stability of CmPC varied with salt concentration and was destabilized by organic acids. Our results indicate that C. merolae is a potential candidate for PC production with thermotolerant properties.