Can glycine betaine denature proteins?

Effects of osmolytes under crowding conditions on the properties of muscle glycogen phosphorylase b

The study of the relationship between the activity and stability of enzymes under crowding conditions in the presence of osmolytes is important for understanding the functioning of a living cell. The effect of osmolytes (trehalose and betaine) on the secondary and tertiary structure and activity of muscle glycogen phosphorylase b (Phb) under crowding conditions created by PEG 2000 and PEG 20000 was investigated using dynamic light scattering, differential scanning calorimetry, circular dichroism spectroscopy, fluorimetry and enzymatic activity assay. At 25 °C PEGs increased Phb activity, but PEG 20000 to a greater extent. Wherein, PEG 20000 significantly destabilized its tertiary and secondary structure, in contrast to PEG 2000. Trehalose removed the effects of PEGs on Phb, while betaine significantly reduced the activating effect of PEG 20000 without affecting the action of PEG 2000. Under heat stress at 48 °C, the protective effect of osmolytes under crowding conditions was more pronounced than at room temperature, and the Phb activity in the presence of osmolytes was higher in these conditions than in diluted solutions. These results provide important insights into the complex mechanism, by which osmolytes affect the structure and activity of Phb under crowding conditions.

Modulation of protein-saccharide interactions by deep-sea osmolytes under high pressure stress

Deep-sea organisms must cope with high hydrostatic pressures (HHP) up to the kbar regime to control their biomolecular processes. To alleviate the adverse effects of HHP on protein stability most organisms use high amounts of osmolytes. Little is known about the effects of these high concentrations on ligand binding. We studied the effect of the deep-sea osmolytes trimethylamine-N-oxide, glycine, and glycine betaine on the binding between lysozyme and the tri-saccharide NAG3, employing experimental and theoretical tools to reveal the combined effect of osmolytes and HHP on the conformational dynamics, hydration changes, and thermodynamics of the binding process. Due to their different chemical makeup, these cosolutes modulate the protein-sugar interaction in different ways, leading to significant changes in the binding constant and its pressure dependence. These findings suggest that deep-sea organisms may down- and up-regulate reactions in response to HHP stress by altering the concentration and type of the intracellular osmolyte.

Effects of Exogenous Application of Glycine Betaine Treatment on 'Huangguoggan' Fruit during Postharvest Storage

Loss of quality in citrus fruit is a common occurrence during postharvest storage due to oxidative stress and energy consumption. In recent years, glycine betaine (GB) has been widely applied to postharvest horticulture fruit. This study aimed to investigate the effect of GB treatment (10 mM and 20 mM) on the quality and antioxidant activity of 'Huangguogan' fruit during postharvest storage at room temperature. Our results indicated that both 10 mM and 20 mM treatments effectively reduced weight and firmness losses and maintained total soluble solid (TSS), titratable acidity (TA), and ascorbic acid contents. Additionally, GB treatment significantly increased the activity of antioxidant enzymes, maintained higher levels of total phenols and total flavonoids, and led to slower accumulation of H2O2. A transcriptome analysis conducted at 28 days after treatment (DAT)identified 391 differentially expressed genes (DEGs) between 20 mM GB (GB-2) and the control (CK) group. These DEGs were enriched in various pathways, particularly related to oxygen oxidoreductase, peroxidase activity, and flavonoid biosynthesis. Overall, the application of GB proved beneficial in enhancing the storability and extending the shelf life of 'Huangguogan' fruit.

Deep sea osmolytes in action: their effect on protein-ligand binding under high pressure stress

Because organisms living in the deep sea and in the sub-seafloor must be able to cope with hydrostatic pressures up to 1000 bar and more, their biomolecular processes, including ligand-binding reactions, must be adjusted to keep the associated volume changes low in order to function efficiently. Almost all organisms use organic cosolvents (osmolytes) to protect their cells from adverse environmental conditions. They counteract osmotic imbalance, stabilize the structure of proteins and maintain their function. We studied the binding properties of the prototypical ligand proflavine to two serum proteins with different binding pockets, BSA and HSA, in the presence of two prominent osmolytes, trimethylamine-N-oxide (TMAO) and glycine betaine (GB). TMAO and GB play an important role in the regulation and adaptation of life in deep-sea organisms. To this end, pressure dependent fluorescence spectroscopy was applied, supplemented by circular dichroism (CD) spectroscopy and computer modeling studies. The pressure-dependent measurements were also performed to investigate the intimate nature of the complex formation in relation to hydration and packing changes caused by the presence of the osmolytes. We show that TMAO and GB are able to modulate the ligand binding process in specific ways. Depending on the chemical make-up of the protein's binding pocket and thus the thermodynamic forces driving the binding process, there are osmolytes with specific interaction sites and binding strengths with water that are able to mediate efficient ligand binding even under external stress conditions. In the binding of proflavine to BSA and HSA, the addition of both compatible osmolytes leads to an increase in the binding constant upon pressurization, with TMAO being the most efficient, rendering the binding process also insensitive to pressurization even up to 2 kbar as the volume change remains close to zero. This effect can be corroborated by the effects the cosolvents impose on the strength and dynamics of hydration water as well as on the conformational dynamics of the protein.

Application of Glycine betaine coated chitosan nanoparticles alleviate chilling injury and maintain quality of plum (Prunus domestica L.) fruit

The use of edible coatings can lead to significant extension of the postharvest life of fresh horticultural products through the regulation of water and gaseous exchange during storage. In this regard, nano-engineered materials are of great interest to design novel and multifunctional edible coatings and are increasingly employed. Chitosan and glycine betaine have been reported to enhance fruit tolerance to chilling stress during cold storage. The current study applied new coating treatments to plum (Prunus domestica L. cv. 'Stanley') fruit at maturity stage in a completely randomized factorial design with three replicates. Plums were treated with distilled water (control), glycine betaine (GB) at 2.5 and 5 mM, chitosan (CTS) at 1% (w/v) or glycine betaine-coated chitosan nanoparticles (CTS-GB NPs) at 0.5 and 1% (w/v) and stored at 1 °C for up to 40 days. The application of CTS-GB NPs (0.5% w/v) was the most effective treatment and induced lower electrolyte leakage, MDA and H₂O₂ content, and significantly alleviated chilling injury. Furthermore, this treatment remarkably increased the activity of PAL enzyme, resulting in higher levels of phenolics, flavonoids and anthocyanins content, and enhanced DPPH scavenging capacity. In addition, CTS-GB NPs treatment increased endogenous GB (9.25 mg g^-1 DW) and proline (1929.29 μg g^-1 FW) accumulation leading to higher activity of CAT, POD, SOD and APX enzymes. Based on the obtained results, the commercial application of CTS-GB NPs could effectively reduce chilling injury, preserve nutritional quality, and prolong the storage potential and shelf life of plum fruit.

An imidazolium-based zwitterionic polymer for antiviral and antibacterial dual functional coatings

To reduce the severe health risk and the huge economic impact associated with the fomite transmission of SARS-CoV-2, an imidazolium-based zwitterionic polymer was designed, synthesized, and demonstrated to achieve contact deactivation of a human coronavirus under dry ambient conditions that resemble fomite transmission. The zwitterionic polymer further demonstrated excellent antifouling properties, reducing the adhesion of coronavirus and the formation of bacteria biofilms under wetted conditions. The polymer was synthesized using a substrate-independent and solvent-free process, leveraging an all-dry technique named initiated chemical vapor deposition (iCVD). The broad applicability of this approach was demonstrated by applying the polymer to a range of substrates that are curved and/or with high-aspect-ratio nano/microporous structures, which remained intact after the coating process. The zwitterionic polymer and the synthesis approach reported here present an effective solution to mitigate viral transmission without the need for manual disinfection, reducing the health and economic impact of the ongoing pandemic.