Bridging the Gap in Cryopreservation Mechanism: Unraveling the Interplay between Structure, Dynamics, and Thermodynamics in Cryoprotectant Aqueous Solutions.

Cryoprotectants play a crucial role in preserving biological material, ensuring their viability during storage and facilitating crucial applications such as the conservation of medical compounds, tissues, and organs for transplantation. However, the precise mechanism by which cryoprotectants modulate the thermodynamic properties of water to impede the formation and growth of ice crystals, thus preventing long-term damage, remains elusive. This is evident in the use of empirically optimized recipes for mixtures that typically contain DMSO, glycerol, and various sugar constituents.

From Local Hydration Motifs in Aqueous Acetic Acid Solutions to Macroscopic Mixing Thermodynamics: A Quantitative Connection from THz-Calorimetry.

We report the results of THz measurements (30-440 cm) of aqueous acetic acid solutions over the full mixing range ( = 0-1). We recorded spectroscopic observables as a function of the acetic acid concentration in the frequency range of the intermolecular stretch at 150 cm and of the librational modes at 350-440 cm. This allowed us to unravel changes in hydrophobic and hydrophilic hydration motifs, respectively.

Impact of hydrophobicity on local solvation structures and its connection with the global solubilization thermodynamics of amphiphilic molecules.

The relationship between the local solvation structures and global thermodynamics, specifically in the case of amphiphilic molecules, is a complex phenomenon and is not yet fully understood. With the prior knowledge that local solvation structures can impose a significant impact on the overall solvation process, we here combine THz spectroscopic analysis with MD simulations to investigate the impact of the altered hydrophobicity and polarity of amphiphilic solute molecules on the local solvation configurations. We use two water soluble alcohols: ethanol (EtOH) and its fluorinated counterpart, 2,2,2-trifluoroethanol (TFE), as model solutes.

Local solvation structures govern the mixing thermodynamics of glycerol-water solutions.

Glycerol is a major cryoprotective agent and is widely used to promote protein stabilization. By a combined experimental and theoretical study, we show that global thermodynamic mixing properties of glycerol and water are dictated by local solvation motifs. We identify three hydration water populations, , bulk water, bound water (water hydrogen bonded to the hydrophilic groups of glycerol) and cavity wrap water (water hydrating the hydrophobic moieties).

Caught in the act: real-time observation of the solvent response that promotes excited-state proton transfer in pyranine.

Photo-induced excited-state proton transfer (ESPT) reactions are of central importance in many biological and chemical processes. Identifying mechanistic details of the solvent reorganizations that facilitate proton transfer however, is challenging for current experimental and theoretical approaches. Using optical pump THz probe (OPTP) spectroscopy and molecular dynamics simulations, we were able to elucidate the ultrafast changes in the solvation environment for three derivatives of pyranine: the photoacid HPTS, the methoxy derivative MPTS, and the photobase OPTS.

Correlating solvation with conformational pathways of proteins in alcohol-water mixtures: a THz spectroscopic insight.

Water, being an active participant in most of the biophysical processes, is important to trace how protein solvation changes as its conformation evolves in the presence of solutes or co-solvents. In this study, we investigate how the secondary structures of two diverse proteins - lysozyme and β-lactoglobulin - change in the aqueous mixtures of two alcohols - ethanol and 2,2,2-trifluoroethanol (TFE) using circular dichroism measurements. We observe that these alcohols change the secondary structures of these proteins and the changes are protein-specific.

Connection of large amplitude angular jump motions with temporal heterogeneity in aqueous solutions.

It has now been established that large angular jumps do take place when a rotating water molecule exchanges its hydrogen bond (H-bond) identity. This motion differs from the small angular diffusional steps occurring within short time intervals which define the 'Debye diffusion model' of water dynamics. We intend to investigate whether these two processes do eventually complement each other.

Soft interaction and excluded volume effect compete as polyethylene glycols modulate enzyme activity.

Polyethylene glycols (PEGs) can either preferentially bind to biomolecules or exert excluded volume effect depending upon their chain length and concentration. We have studied the effect of ethylene glycol (EG) and PEGs of different chain lengths (M 400 and 4000) on the enzyme efficiency of hen-egg-white lysozyme (HEWL) on Micrococcus lysodeikticus (M. Lys.

Effect of Phospholipid Headgroup Charge on the Structure and Dynamics of Water at the Membrane Interface: A Terahertz Spectroscopic Study.

Biological membranes are highly organized supramolecular assemblies of lipids and proteins. The membrane interface separates the outer (bulk) aqueous phase from the hydrophobic membrane interior. In this work, we have explored the microstructure and collective dynamics of the membrane interfacial hydration shell in zwitterionic and negatively charged phospholipid membrane bilayers using terahertz time-domain spectroscopy.

Decisive Role of Hydrophobicity on the Effect of Alkylammonium Chlorides on Protein Stability: A Terahertz Spectroscopic Finding.

Many biologically important processes involve a subtle interplay between Columbic and hydrophobic interactions among molecular groups with water. A comprehensive understanding of such processes, specially while occurring simultaneously in the same molecule is of practical importance. In this contribution, we report the ultrafast (subpicosecond to picosecond) collective hydrogen bond dynamics of water in the extended hydration layers in a series of alkylammonium chloride salts using THz time domain spectroscopic (TTDS) technique (0.

Collective hydration dynamics in some amino acid solutions: A combined GHz-THz spectroscopic study.

A detailed understanding of hydration of amino acids, the building units of protein, is a key step to realize the overall solvation processes in proteins. In the present contribution, we have made a combined GHz (0.2-50) to THz (0.

Nonmonotonic Hydration Behavior of Bovine Serum Albumin in Alcohol/Water Binary Mixtures: A Terahertz Spectroscopic Investigation.

We report the experimental observation of nonmonotonic changes in the collective hydration of bovine serum albumin (BSA) in the presence of alcohols of varying carbon-chain lengths, that is, ethanol, 2-propanol, and tert-butyl alcohol (TBA), by using terahertz (THz) time domain spectroscopy. We measured the THz absorption coefficient (α) of the protein solutions, and it was observed that α fluctuated periodically as a function of alcohol concentration at a fixed protein concentration. For a fixed alcohol concentration, an increase in the protein concentration resulted in nonmonotonic changes in α; thus, it first decreased rapidly and then increased, which was followed by a shallow decrease.

Non-monotonic dynamics of water in its binary mixture with 1,2-dimethoxy ethane: A combined THz spectroscopic and MD simulation study.

A combined experimental (mid- and far-infrared FTIR spectroscopy and THz time domain spectroscopy (TTDS) (0.3-1.6 THz)) and molecular dynamics (MD) simulation technique are used to understand the evolution of the structure and dynamics of water in its binary mixture with 1,2-dimethoxy ethane (DME) over the entire concentration range.

Effect of Short Chain Poly(ethylene glycol)s on the Hydration Structure and Dynamics around Human Serum Albumin.

We report the changes in the hydration dynamics around a globular protein, human serum albumin (HSA), in the presence of two short chain crowding agents, namely poly(ethylene glycol)s (PEG 200 and 400). The change in the network water structure is investigated using FTIR spectroscopy in the far-infrared (FIR) frequency range. Site specific changes are obtained by time-resolved fluorescence spectroscopic technique using the intrinsic fluorophore tryptophan (Trp214) of HSA.

Does urea alter the collective hydrogen-bond dynamics in water? A dielectric relaxation study in the terahertz-frequency region.

We report the ultrafast collective hydrogen-bond dynamics of water in the extended hydration layer of urea by using terahertz time-domain spectroscopy in the frequency region of 0.3-2.0 THz.

Collective hydration dynamics of guanidinium chloride solutions and its possible role in protein denaturation: a terahertz spectroscopic study.

The remarkable ability of guanidinium chloride (GdmCl) to denature proteins is a well studied yet controversial phenomenon; the exact molecular mechanism is still debatable, especially the role of hydration dynamics, which has been paid less attention. In the present contribution, we have addressed the issue of whether the collective hydrogen bond dynamics of water gets perturbed in the presence of GdmCl and its possible impact on the denaturation of a globular protein human serum albumin (HSA), using terahertz (THz) time domain spectroscopy (TTDS) in the frequency range of 0.3-2.

Short chain polyethylene glycols unusually assist thermal unfolding of human serum albumin.

In the present study we have investigated the thermal stability of the globular transport protein human serum albumin (HSA), in the presence of two small chain polyethylene glycols (namely PEG 200 and PEG 400). Both near- and far-UV circular dichroism (CD) study reveal that addition of PEG moderately increases the α-helical content of the protein without abruptly changing its tertiary structure. The hydration structure at the protein surface experiences a notable change at 30% PEG (v/v) concentration as evidenced from compressibility and dynamic light scattering (DLS) measurements.