Low-Density Water Structure Observed in a Nanosegregated Cryoprotectant Solution at Low Temperatures from 285 to 238 K.

The structure of liquid water is defined by its molecular association through hydrogen bonding. Two different structures have been proposed for liquid water at low temperatures: low-density liquid (LDL) and high-density liquid (HDL) water. Here, we demonstrate a platform that can be exploited to experimentally probe the structure of liquid water in equilibrium at temperatures down to 238 K. We make use of a cryoprotectant molecule, glycerol, that, when mixed with water, lowers the freezing temperature of the solution nonmonotonically with glycerol concentration. We use a combination of neutron diffraction measurements and computational modeling to examine the structure of water in glycerol-water liquid mixtures at low temperatures from 285 to 238 K. We confirm that the mixtures are nanosegregated into regions of glycerol-rich and water-rich clusters. We examine the water structure and reveal that, at the temperatures studied here, water forms a low-density water structure that is more tetrahedral than the structure at room temperature. We postulate that nanosegregation allows water to form a low-density structure that is protected by an extensive and encapsulating glycerol interface.

Molecular insight into the hydrogen bonding and micro-segregation of a cryoprotectant molecule.

Glycerol-water liquid mixtures are intriguing hydrogen-bonded systems and essential in many fields of chemistry, ranging from basic molecular research to widespread use in industrial and biomedical applications as cryoprotective solutions. Despite much research on these mixtures, the details of their microscopic structure are still not understood. One common notion is that glycerol acts to diminish the hydrogen bonding ability of water, a recurring hypothesis that remains untested by direct experimental approaches. The present work characterizes the structure of glycerol-water mixtures, across the concentration range, using a combination of neutron diffraction experiments and computational modeling. Contrary to previous expectations, we show that the hydrogen bonding ability of water is not diminished in the presence of glycerol. We show that glycerol-water hydrogen bonds effectively take the place of water-water hydrogen bonds, allowing water to maintain its full hydrogen bonding capacity regardless of the quantity of glycerol in the environment. We provide a quantitative measurement of all hydrogen bonding in the system and reveal a concentration range where a microsegregated, bipercolating liquid mixture exists in coexistence with a considerable interface region. This work highlights the role of hydrogen bonding connectivity rather than water structuring/destructuring effects in these important cryoprotective systems.

The hydrogen-bonding ability of the amino acid glutamine revealed by neutron diffraction experiments.

Hydrogen bonding between glutamine residues has been identified as playing an important role in the intermolecular association and aggregation of proteins. To establish the molecular mechanisms of glutamine interactions, neutron diffraction coupled with hydrogen/deuterium isotopic substitution in combination with computational modeling has been used to investigate the structure and hydration of glutamine in aqueous solution. The final structures obtained are consistent with the experimental data and provide insight into the hydrogen-bonding ability of glutamine. We find that the backbone of glutamine is able to coordinate more water molecules than the side chain, suggesting that charged groups on the glutamine molecule are more successful in attracting water than the dipole in the side chain. In both the backbone and the side chain, we find that the carbonyl groups interact more readily with water molecules than the amine groups. We find that glutamine-glutamine interactions are present, despite their low concentration in this dilute solution. This is evidenced through the occurrence of dimers of glutamine molecules in the solution, demonstrating the effective propensity of this molecule to associate through backbone-backbone, backbone-side chain, and side chain-side chain hydrogen bond interactions. The formation of dimers of glutamine molecules in such a dilute solution (30 mg/mL glutamine) may have implications in the aggregation of glutamine-rich proteins in neurological diseases where aggregation is prevalent.

Structural examination of the impact of glycerol on water structure.

The sugar alcohol glycerol is essential for cryopreservation, an important process used for the storage of biological molecules, cells, or tissues at low temperatures. A key hypothesis for the cryoprotective action of glycerol is that the glycerol molecule acts to modify the hydrogen bonding ability of water molecules, thus inhibiting ice formation. In this study, high-resolution neutron diffraction has been used in conjunction with hydrogen/deuterium isotopic labeling to determine with unprecedented detail the structure of a dilute aqueous glycerol solution. Contrary to some expectations, at the first neighbor level no modification in the position of the coordination shell of water is observed. However, at the second neighbor level the presence of only small quantities of glycerol in the solution has the same impact on water structure as increasing the pressure. Evidence is also found of more glycerol monomers than would be expected in the solution. This prevalence of isolated glycerol molecules results in a very well mixed solution with glycerol-water hydrogen bond interactions being very favorable. Our results indicate that while the local structure of water is relatively unperturbed by the presence of glycerol, the hydrogen bonded network is highly mixed between glycerol and water. These results indicate that efforts to explain the action of glycerol should focus on not just local water structure, but the extended hydrogen bonded network in the system.

Preference for isolated water molecules in a concentrated glycerol-water mixture.

Neutron diffraction coupled with hydrogen/deuterium isotopic substitution has been used to investigate the structure of a concentrated glycerol water (4:1 mole fraction) solution. The neutron diffraction data were used to constrain a three-dimensional computational model that is experimentally relevant using the empirical potential structure refinement technique. From interrogation of this model, we find that glycerol-glycerol hydrogen bonding is largely unperturbed by the presence of water in the solution. We find that glycerol-water hydrogen bonding is prevalent, suggesting that water molecules effectively take the place of glycerol molecules in this concentrated solution. In contrast, we find that water-water hydrogen bonding is significantly perturbed. While the first coordination shell of water in the concentrated solution remains similar to that of pure water, water-water hydrogen bonding is greatly diminished beyond the first neighbor distance. Interestingly, the majority of water molecules exist as single monomers in the concentrated glycerol solution. The preference of isolated water molecules results in a solution that is well mixed with optimal glycerol-water hydrogen bonding. These results highlight the importance of preferential hydrogen bonding in aqueous solutions and suggest a mechanism for cryoprotection by which glycerol effectively hydrogen bonds with water, resulting in a disrupted hydrogen-bonded water network.

The structure of glycerol in the liquid state: a neutron diffraction study.

Neutron diffraction coupled with hydrogen/deuterium isotopic substitution has been used to investigate the structure of the pure cryoprotectant glycerol in the liquid state at 298 K and 1 atm. The neutron diffraction data were used to constrain a 3 dimensional computational model that is experimentally relevant using the empirical potential structure refinement (EPSR) technique. These simulations lead to a model structure of the glycerol molecule that is consistent with the experimental data. Interestingly, from interrogation of this structure, it is found that the number of hydrogen bonds per molecule is larger than had previously been suggested. Furthermore, converse to previous work, no evidence for intra-molecular hydrogen bonds is found. These results highlight the importance and relevance of using experimental data to inform computational modelling of even simple liquid systems.

Segregation in aqueous methanol enhanced by cooling and compression.

Molecular segregation in methanol-water mixtures is studied across a wide concentration range as a function of temperature and pressure. Cluster distributions obtained from both neutron diffraction and molecular dynamics simulations point to significantly enhanced segregation as the mixtures are cooled or compressed. This evolution toward greater molecular heterogenity in the mixture accounts for the observed changes in the water-water radial distribution function and there are indications also of a change in the topology of the water clusters. The observed behavior is consistent with an approach to an upper critical solution point. Such a point would appear to be "hidden" below the freezing line, thereby precluding observation of the two-fluid region.

Methanol-water solutions: a bi-percolating liquid mixture.

An extensive series of neutron diffraction experiments and molecular dynamics simulations has shown that mixtures of methanol and water exhibit extended structures in solution despite the components being fully miscible in all proportions. Of particular interest is a concentration region (methanol mole fraction between 0.27 and 0.54) where both methanol and water appear to form separate, percolating networks. This is the concentration range where many transport properties and thermodynamic excess functions reach extremal values. The observed concentration dependence of several of these material properties of the solution may therefore have a structural origin.

Case management for dually diagnosed individuals involved in the criminal justice system.

A case-management model for individuals with substance abuse and mental health disorders who are involved in the criminal justice system is described, based on the experience of a rural demonstration project. Detailed descriptions of case-management activities and the philosophy underlying this model of case management are provided. A major goal of these case-management services was to improve access to appropriate treatment for the target population. Evaluation data describing the population served, case-management implementation, and outcomes are presented along with a case vignette. Six-month follow-up data revealed significantly fewer legal problems and apparent symptom relief for participants in the project. Participants reported improvement in most life areas measured compared to the year before, and were generally satisfied with the case-management services. Barriers observed in implementing these types of services and issues for replication are outlined and discussed.

Incidence and outcome of multiple myeloma in Western Australia, 1960 to 1984.

All patients diagnosed with multiple myeloma in Western Australia have been registered since 1960; 337 men and 280 women were registered in the period 1960-84. During this period there was a 25% increase in incidence. Age adjusted incidence rates rose from 2.34 per 100,000 person years in men and 1.64 in women during the decade 1960-69 to 2.95 in men and 1.92 in women in 1980-84. Overall, the incidence was 1.36 times higher in men than in women (95% confidence interval 1.16-1.59). Survival from multiple myeloma improved substantially during the period. In 1960-69, median survival for both sexes was six months, in 1970-79 it was 19 months, and in 1980-84 median survival in men was 43 months while in women it was at least five years.

Interpersonal linkage among Hodgkin's disease patients and controls in Western Australia.

Interpersonal linkages were studied in 178 Hodgkin's disease patients, aged 60 years or younger, who lived in Western Australia between 1964 and 1975, and in their matched controls. Eighty-nine living subjects were interviewed about places and periods of residence, school attendance and employment, and possible linkages were computed based on concurrence of these events. Subjects were also shown the names of all patients and controls and asked to mark the names they recognized, giving details of acquaintanceships. The acquaintanceship method yielded more and the concurrence method fewer case-case links than expected. Little overlap occurred in linkages identified by the two methods. The acquaintanceship method is thought to be the more reliable. Risk factors suggested in the literature were also investigated. Increased risk of Hodgkin's disease in living patients was associated with being unmarried, being born outside Western Australia, smoking cigarettes, and having lived and worked on a farm and worked with animals. These effects did not explain the excess of case-case linkages found by the acquaintanceship method.

The effect of diagnostic review on the estimated incidence of lymphatic and hematopoietic neoplasms in Western Australia.

Diagnoses of 1443 patients from a population-based leukemia and allied disorders registry in Western Australia were subjected to diagnostic review, resulting in 235 deletions, 120 changes in diagnosis, and 23 undecided diagnoses. Deletions occurred mainly in lymphoma registrations, most of these being reclassified as other cancers. Among the patients whose names were deleted, 196 deaths occurred of whom 67 had leukemia or an allied disorder as the certified cause of death. Lymphoma incidence rates in Western Australia were lower than those reported from another Australian registry. Quality control of registration and special interests in diagnosis or classification of particular tumors may affect their reported incidence rates.

Myelofibrosis in Western Australia: an epidemiological study of 29 cases.

Survival figures and other epidemiological features are described for 29 patients with myelofibrosis living in Western Australia during the period 1959 to 1963. These patients form part of a larger series of 509 patients with leukaemia and allied disorders. The diagnostic incidence rate was found to be 0.5 per 100,000 population, the mortality rate was 0.4 per 100,000 and the prevalence 1.8 per 100,000. Comparison with related myeloproliferative disorders shows that myelofibrosis occurs somewhat less frequently than chronic granulocytic leukaemia and considerably less so than polycythaemia vera. The sex ratio indicates a small male preponderance and the age distribution is similar to that in other descriptions. Survival times for all patients accord with those reported in the literature, but this series showed a marked female advantage in survival. Findings in other series are described.