Unique aqueous self-assembly behavior of a thermoresponsive diblock copolymer

It is well-recognized that block copolymer self-assembly in solution typically produces spheres, worms or vesicles, with the relative volume fraction of each block dictating the copolymer morphology. Stimulus-responsive diblock copolymers that can undergo either sphere/worm or vesicle/worm transitions are also well-documented. Herein we report a new amphiphilic diblock copolymer that can form spheres, worms, vesicles or lamellae in aqueous solution. Such self-assembly behavior is unprecedented for a single diblock copolymer of fixed composition yet is achieved simply by raising the solution temperature from 1 °C (spheres) to 25 °C (worms) to 50 °C (vesicles) to 70 °C (lamellae). Heating increases the degree of hydration (and hence the effective volume fraction) of the core-forming block, with this parameter being solely responsible for driving the sphere-to-worm, worm-to-vesicle and vesicle-to-lamellae transitions. The first two transitions exhibit excellent reversibility but the vesicle-to-lamellae transition exhibits hysteresis on cooling. This new thermoresponsive diblock copolymer provides a useful model for studying such morphological transitions and is likely to be of significant interest for theoretical studies

Antioxidant efficacy and adhesion rescue by a recombinant mussel foot protein-6

Mytilus foot protein type 6 (mfp-6) is crucial for maintaining the reducing conditions needed for optimal wet adhesion in marine mussels. In this report we describe the expression and production of a recombinant Mytilus californianus foot protein type 6 variant 1 (rmfp-6.1) fused with a hexa-histidine affinity tag in Escherichia coli and its purification by affinity chromatography. Recombinant mfp-6 showed high purification yields of 5–6 mg/L cell culture and excellent solubility in low pH buffers that retard oxidation of its many thiol groups. Purified rmfp-6.1 protein showed high DPPH radical scavenging activity as compared to Vitamin C. Using the highly sensitive surface force apparatus (SFA) technique to measure interfacial surface forces in the nanoNewton range we show that rmfp-6.1 is also able to rescue the oxidation-dependent adhesion loss of mussel foot protein 3 (mfp-3) at pH 3. The adhesion rescue is related to a reduction of dopaquinone back to DOPA in mfp-3 which is the reverse reaction observed during the detrimental enzymatic browning process in fruits and vegetables. Broadly viewed, rmfp-6.1 has potential as a versatile antioxidant for applications ranging from personal products to anti-spoilants for perishable foods during processing and storage