Trimethylamine N-oxide (TMAO) doubly locks the hydrophobic core and surfaces of protein against desiccation stress.

Interactions between proteins and osmolytes are ubiquitous within cells, assisting in response to environmental stresses. However, our understanding of protein-osmolyte interactions underlying desiccation tolerance is limited. Here, we employ solid-state NMR (ssNMR) to derive information about protein conformation and site-specific interactions between the model protein, SH3, and the osmolyte trimethylamine N-oxide (TMAO).

Preparation of Single-Helical Curdlan Hydrogel and Its Activation with Coagulation Factor G.

β-1,3-glucans are a kind of natural polysaccharide with immunomodulatory, antitumor, and anti-inflammatory properties. Curdlan, as the simplest linear β-1,3-glucan, possesses a variety of biological activities and thermogelation properties. However, due to the complexity and variability of the conformations of curdlan, the exact structure-activity relationship remains unclear.

Preparation and characterization of curdlan with unique single-helical conformation and its assembly with Congo Red.

Elucidating the structure-activity relationship of curdlan is hampered by a lack of characterization with unique specific conformations (i.e., single- or triple-helix).

Dynamic mechanism of halide salts on the phase transition of protein models, poly(N-isopropylacrylamide) and poly(N,N-diethylacrylamide).

The effects of salts on protein systems are not yet fully understood. We investigated the ionic dynamics of three halide salts (NaI, NaBr, and NaCl) with two protein models, namely poly(N-isopropylacrylamide) (PNIPAM) and poly(N,N-diethylacrylamide) (PDEA), using multinuclear NMR, dispersion corrected density functional theory (DFT-D) calculations and dynamic light scattering (DLS) methods. The variation in ionic line-widths and chemical shifts induced by the polymers clearly illustrates that anions rather than cations interact directly with the polymers.

Inverse solubility of chitin/chitosan in aqueous alkali solvents at low temperature.

The low-temperature dissolving mechanism of chitin/chitosan in the alkali (LiOH, NaOH and KOH) aqueous solvents has not been well established yet. As revealed by our XRD and NMR methods, the prepared deacetylated chitins can be categorized as chitin (DA = 0.94-0.

Preferential adsorption of the additive is not a prerequisite for cononsolvency in water-rich mixtures.

Cononsolvency of poly(N-isopropylacrylamide) (PNIPAM) gels in binary mixed solvents (water-acetone and water-DMSO) has been comparatively investigated by H HR-MAS NMR spectroscopy. The results demonstrate that, although the addition of both acetone and DMSO gives rise to cononsolvency behavior, PNIPAM preferentially interacts with acetone rather than DMSO in a water-rich regime, regardless of whether the temperature is above or below the volume phase transition temperature (VPTT). It suggests that the preferential adsorption of the additive cannot be deemed as a prerequisite for the cononsolvency in water-rich mixtures.

Inhomogeneous-collapse driven micelle-vesicle transition of amphiphilic block copolymers.

Understanding the morphological transition dynamics related to the hydrophilic-hydrophobic interface has been a challenge due to the lack of an effective evaluation method. Herein, nuclear magnetic resonance spectroscopy was employed to study the morphological transition related chain collapse of poly(N,N'-diethylaminoethylmethacrylate)-b-poly(N-isopropylacrylamide) (PDEAEMA-b-PNIPA) and poly(N,N'-dimethylaminoethylmethacrylate)-b-poly(N-isopropylacrylamide) (PDMAEMA-b-PNIPA) and was proved to be a powerful technique in morphological transition mechanism studies once combined with dynamic light scattering and transmission electron microscopy. Unlike the cooperative coil collapse of two blocks in the PDMAEMA-b-PNIPA alkaline solution upon heating which induces the assembly of a nanostructure (∼200 nm) with a hydrophobic core containing both collapsed PDMAEMA and PNIPA segments and a hydrophilic surface part consisting of un-shrunk PDMAEMA and PNIPA segments, PDEAEMA-b-PNIPA with a low-temperature core-shell micelle structure showed a micelle-vesicle transition due to temperature-induced inhomogeneous-collapse of PNIPA.

1H MAS NMR studies of the phase separation of poly(N-isopropylacrylamide) gel in binary solvents.

Preferential interactions of solvents with poly(N-isopropylacrylamide) (PNIPAM) gel networks in binary water/alcohol (water/methanol and water/ethanol) mixtures have been investigated using variable-temperature high-resolution 1H MAS NMR. NMR results for PNIPAM gel in the binary solvents reveal the existence of two distinct types of water/alcohol mixtures above the LCST: confined binary solvents bound inside the gel, and free binary solvents expelled from the gel. It is interesting to find that the alcohol concentration in confined solution is significantly higher than that in free solution.