Mode coupling behavior and fragile to strong transition of trehalose in a binary mixture with water upon supercooling.

We perform molecular dynamics simulations of a binary mixture of water and trehalose with the TIP4P/Ice water model. We analyze the slow dynamics of trehalose molecules in the mildly supercooled region for concentrations of 3.66 and 18.57 wt. %. We previously studied the dynamics of water in the same mixtures. Supercooled TIP4P/Ice water solvating trehalose molecules was found to follow the Mode Coupling Theory (MCT) and to undergo a transition from a fragile to a strong behavior for both concentrations. Here, we show that also the dynamics of trehalose molecules follows the MCT and displays a fragile to strong crossover (FSC). The results show that trehalose in binary mixtures with water shares with it the dynamical behavior typical of glass forming liquids. Moreover, the FSC for trehalose structural relaxation times is found to occur at temperatures close to those previously obtained for water in the same solutions, showing that the dynamics of the solute is strongly coupled to that of the solvent. We also perform a MCT test showing that the trehalose dynamics obeys the MCT time-temperature superposition principle and that the exponents derived from the theory and the ones obtained from fitting procedure of the relaxation times are comparable, confirming that trehalose molecules in supercooled water solutions follow the MCT of glassy dynamics. Moreover, as predicted by the theory, trehalose particles have MCT parameters comparable to those of water in the same mixtures. This is an important result, given that MCT was originally formulated for monoatomic particles.

Structure and slow dynamics of protein hydration water with cryopreserving DMSO and trehalose upon cooling.

We study, through molecular dynamics simulations, three aqueous solutions with one lysozyme protein and three different concentrations of trehalose and dimethyl sulfoxide (DMSO). We analyze the structural and dynamical properties of the protein hydration water upon cooling. We find that trehalose plays a major role in modifying the structure of the network of HBs between water molecules in the hydration layer of the protein. The dynamics of hydration water presents, in addition to the α-relaxation, typical of glass formers, a slower long-time relaxation process, which greatly slows down the dynamics of water, particularly in the systems with trehalose, where it becomes dominant at low temperatures. In all the solutions, we observe, from the behavior of the α-relaxation times, a shift of the Mode Coupling Theory crossover temperature and the fragile-to-strong crossover temperature toward higher values with respect to bulk water. We also observe a strong-to-strong crossover from the temperature behavior of the long-relaxation times. In the aqueous solution with only DMSO, the transition shifts to a lower temperature than in the case with only lysozyme reported in the literature. We observe that the addition of trehalose to the mixture has the opposite effect of restoring the original location of the strong-to-strong crossover. In all the solutions analyzed in this work, the observed temperature of the protein dynamical transition is slightly shifted at lower temperatures than that of the strong-to-strong crossover, but their relative order is the same, showing a correlation between the motion of the protein and that of the hydration water.

Discovery and Optimization of Pyridazinones as PI3Kδ Selective Inhibitors for Administration by Inhalation.

A hit-to-lead campaign pursuing the identification of novel inhalant small-molecule phosphatidylinositol 3-kinase (PI3K) inhibitors for the treatment of inflammatory respiratory diseases is disclosed. A synthetically versatile pyridazin-3(2H)-one scaffold was designed, and three exit vectors on the core moiety were used to explore chemical diversity and optimize pharmacological and absorption, distribution, metabolism, and excretion (ADME) properties. Desired modulation of PI3Kδ selectivity and cellular potency as well as ADME properties in view of administration by inhalation was achieved. Intratracheal administration of lead compound 26 resulted in a promising pharmacokinetic profile, thus demonstrating that the optimization strategy of in vitro profiles successfully translated to an in vivo setting.

Incidence of new-onset hypertension before, during, and after the COVID-19 pandemic: a 7-year longitudinal cohort study in a large population.

BACKGROUND: While the augmented incidence of diabetes after COVID-19 has been widely confirmed, controversial results are available on the risk of developing hypertension during the COVID-19 pandemic. METHODS: We designed a longitudinal cohort study to analyze a closed cohort followed up over a 7-year period, i.e., 3 years before and 3 years during the COVID-19 pandemic, and during 2023, when the pandemic was declared to be over. We analyzed medical records of more than 200,000 adults obtained from a cooperative of primary physicians from January 1, 2017, to December 31, 2023. The main outcome was the new diagnosis of hypertension. RESULTS: We evaluated 202,163 individuals in the pre-pandemic years and 190,743 in the pandemic years, totaling 206,857 when including 2023 data. The incidence rate of new hypertension was 2.11 (95% C.I. 2.08-2.15) per 100 person-years in the years 2017-2019, increasing to 5.20 (95% C.I. 5.14-5.26) in the period 2020-2022 (RR = 2.46), and to 6.76 (95% C.I. 6.64-6.88) in 2023. The marked difference in trends between the first and the two successive observation periods was substantiated by the fitted regression lines of two Poisson models conducted on the monthly log-incidence of hypertension. CONCLUSIONS: We detected a significant increase in new-onset hypertension during the COVID-19 pandemic, which at the end of the observation period affected ~ 20% of the studied cohort, a percentage higher than the diagnosis of COVID-19 infection within the same time frame. This observation suggests that increased attention to hypertension screening should not be limited to individuals who are aware of having contracted the infection but should be extended to the entire population.

A New Tool to Identify Pediatric Patients with Atypical Diabetes Associated with Gene Polymorphisms.

Background: Recent diabetes subclassifications have improved the differentiation between patients with type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus despite several overlapping features, yet without considering genetic forms of diabetes. We sought to facilitate the identification of monogenic diabetes by creating a new tool that we validated in a pediatric maturity-onset diabetes of the young (MODY) cohort. Methods: We first created the DIAgnose MOnogenic DIAbetes (DIAMODIA) criteria based on the pre-existing, but incomplete, MODY calculator. This new score is composed of four strong and five weak criteria, with patients having to display at least one weak and one strong criterion. Results: The effectiveness of the DIAMODIA criteria was evaluated in two patient cohorts, the first consisting of patients with confirmed MODY diabetes (n=34) and the second of patients with T1DM (n=390). These DIAMODIA criteria successfully detected 100% of MODY patients. Multiple correspondence analysis performed on the MODY and T1DM cohorts enabled us to differentiate MODY patients from T1DM. The three most relevant variables to distinguish a MODY from T1DM profile were: lower insulin-dose adjusted A1c score ≤9, glycemic target-adjusted A1c score ≤4.5, and absence of three anti-islet cell autoantibodies. Conclusion: We validated the DIAMODIA criteria, as it effectively identified all monogenic diabetes patients (MODY cohort) and succeeded to differentiate T1DM from MODY patients. The creation of this new and effective tool is likely to facilitate the characterization and therapeutic management of patients with atypical diabetes, and promptly referring them for genetic testing which would markedly improve clinical care and counseling, as well.

Long-Lasting Control of LDL Cholesterol Induces a 40% Reduction in the Incidence of Cardiovascular Events: New Insights from a 7-Year Study.

Recent studies have yielded controversial results on the long-term effects of statins on the risk of cardiovascular (CV) events. To fill this knowledge gap, we assessed the relationship between low-density lipoprotein cholesterol (LDL-C) levels and CV events in hypertensive patients without previous CV events and naïve to antidyslipidemic treatment within the "Campania Salute Network" in Southern Italy. We studied 725 hypertensive patients with a mean follow-up of 85.4 ± 25.7 months. We stratified our cohort into three groups based on LDL cholesterol (LDL-C) levels in mg/dl: group 1) patients showing during the follow-up a mean LDL-C value ≤100 mg/dl in absence of statin therapy; group 2) statin-treated patients with LDL ≤100 mg/dl; and group 3) patients with LDL-C >100 mg/dl. No significant difference among the groups was observed in terms of demographic and clinical characteristics and medications. The incidence of first CV events was 5.7% in group 1, 6.0% in group 2, and 11.9% in group 3 (P < 0.05 vs. group 1 and group 2). A stable long-term satisfactory control of LDL-C plasma concentration (≤100 mg/dl) reduced the incidence of major CV events from one event every 58.6 patients per year to one event every 115.9 patients per year. These findings were confirmed in a Cox regression analysis, adjusting for potential confounding factors. Collectively, our data demonstrate that a 7-year stable control of LDL-C reduces the incidence of CV events by 40%. SIGNIFICANCE STATEMENT: There are several discrepancies between Mendelian studies and other investigations concerning the actual effects of reduction of plasma concentration of low-density lipoprotein (LDL) cholesterol on the incidence of major cardiovascular events. Taken together, our data in nondiabetic subjects show that a 7-year stable control of LDL cholesterol induces a ∼40% reduction of the incidence of cardiovascular events.

Achieving a Systolic Blood Pressure Below 130 mmHg Reduces the Incidence of Cardiovascular Events in Hypertensive Patients with Echocardiographic Left Ventricular Hypertrophy.

Background: Recent reports have evidenced an increased mortality rate in hypertensive patients with electrocardiographic left ventricular hypertrophy (ECG-LVH) achieving systolic blood pressure (SBP) <130 mmHg. However, to the best of our knowledge, the actual effects of blood pressure reduction to the ≤130/80 mmHg target on the incidence of cardiovascular (CV) events have never been determined in hypertensive patients with a diagnosis of left ventricular hypertrophy based on echocardiographic criteria (Echo-LVH). Methods: To fill this long-standing knowledge gap, we harnessed a population of 9511 hypertensive patients, followed-up for 33.6 [interquartile range 7.9-72.7] months. The population was divided into six groups according to the average SBP achieved during the follow-up (≤130, 130-139, and ≥140 mmHg) and absence/presence of Echo-LVH. The primary endpoint was a composite of fatal or nonfatal myocardial infarction and stroke, sudden cardiac death, heart failure requiring hospitalization, revascularization, and carotid stenting. Secondary endpoints included atrial fibrillation and transient ischemic attack. Results: During the follow-up, achieved SBP and diastolic blood pressure (DBP) were comparable between patients with and without Echo-LVH. Strikingly, the rates of primary and secondary endpoints were significantly higher in patients with Echo-LVH and SBP >130 mmHg, reaching the highest values in the Echo-LVH group with SBP ≥140 mmHg. By separate Cox multivariable regressions, after adjusting for potential confounders, both primary and secondary endpoints were significantly associated with SBP ≥140 mmHg and Echo-LVH. Instead, DBP reduction ≤80 mmHg was associated with a significant increased rate of secondary events. Conclusions: In hypertensive patients with Echo-LVH, achieving an average in-treatment SBP target ≤130 mmHg has a beneficial prognostic impact on incidence of CV events. SIGNIFICANCE STATEMENT: Contrary to recent findings, achieving in-treatment SBP ≤130 mmHg lowers the incidence of CV events in hypertensive patients with Echo-LVH. However, reducing DBP ≤80 mmHg is linked to increased CV complications. Cox multivariable regression models, considering potential confounders, reveal that the rate of hard and soft CV events is significantly associated with Echo-LVH and SBP ≥140 mmHg. Our data indicate that therapeutic strategies for Echo-LVH patients should target SBP ≤130 mmHg while avoiding lowering DBP ≤80 mmHg.

Incidence of type 2 diabetes before and during the COVID-19 pandemic in Naples, Italy: a longitudinal cohort study.

Background: The association of COVID-19 with the development of new-onset diabetes has been recently investigated by several groups, yielding controversial results. Population studies currently available in the literature are mostly focused on type 1 diabetes (T1D), comparing patients with a SARS-CoV-2 positive test to individuals without COVID-19, especially in paediatric populations. In this study, we sought to determine the incidence of type 2 diabetes (T2D) before and during the COVID-19 pandemic. Methods: In this longitudinal cohort study, we analysed a cohort followed up over a 6-year period using an Interrupted Time Series approach, i.e. 3-years before and 3-years during the COVID-19 pandemic. We analysed data obtained from >200,000 adults in Naples (Italy) from January 1st 2017 to December 31st 2022. In this manner, we had the opportunity to compare the incidence of newly diagnosed T2D before (2017-2019) and during (2020-2022) the COVID-19 pandemic. The key inclusion criteria were age >18-year-old and data availability for the period of observation; patients with a diagnosis of diabetes obtained before 2017 were excluded. The main outcome of the study was the new diagnosis of T2D, as defined by the International Classification of Diseases 10 (ICD-X), including prescription of antidiabetic therapies for more than 30 days. Findings: A total of 234,956 subjects were followed-up for at least 3-years before or 3-years during the COVID-19 pandemic and were included in the study; among these, 216,498 were analysed in the pre-pandemic years and 216,422 in the pandemic years. The incidence rate of T2D was 4.85 (95% CI, 4.68-5.02) per 1000 person-years in the period 2017-2019, vs 12.21 (95% CI, 11.94-12.48) per 1000 person-years in 2020-2022, with an increase of about twice and a half. Moreover, the doubling time of the number of new diagnoses of T2D estimated by unadjusted Poisson model was 97.12 (95% CI, 40.51-153.75) months in the prepandemic period vs 23.13 (95% CI, 16.02-41.59) months during the COVID-19 pandemic. Interestingly, these findings were also confirmed when examining patients with prediabetes. Interpretation: Our data from this 6-year study on more than 200,000 adult participants indicate that the incidence of T2D was significantly higher during the pandemic compared to the pre-COVID-19 phase. As a consequence, the epidemiology of the disease may change in terms of rates of outcomes as well as public health costs. COVID-19 survivors, especially patients with prediabetes, may require specific clinical programs to prevent T2D. Funding: The US National Institutes of Health (NIH: NIDDK, NHLBI, NCATS), Diabetes Action Research and Education Foundation, Weill-Caulier and Hirschl Trusts.

Glassy dynamics of water in TIP4P/Ice aqueous solutions of trehalose in comparison with the bulk phase.

We perform molecular dynamics simulations of TIP4P/Ice water in solution with trehalose for 3.65 and 18.57 wt. % concentrations and of bulk TIP4P/Ice water at ambient pressure, to characterize the structure and dynamics of water in a sugar aqueous solution in the supercooled region. We find here that TIP4P/Ice water in solution with trehalose molecules follows the Mode Coupling Theory and undergoes a fragile to strong transition up to the highest concentration investigated, similar to the bulk. Moreover, we perform a Mode Coupling Theory test, showing that the Time Temperature Superposition principle holds for both bulk TIP4P/Ice water and for TIP4P/Ice water in the solutions and we calculate the exponents of the theory. The direct comparison of the dynamical results for bulk water and water in the solutions shows upon cooling along the isobar a fastening of water dynamics for lower temperatures, T < 240 K. We found that the counter-intuitive behavior for the low temperature solutions can be explained with the diffusion anomaly of water leading us to the conclusion that the fastening observed below T = 240 K in water dynamics is only fictitious, due to the fact that the density of water molecules in the solutions is higher than the density of the bulk at the same temperature and pressure. This result should be taken into account in experimental investigations which are often carried out at constant pressure.

Phase Diagram of Aqueous Solutions of LiCl: a Study of Concentration Effects on the Anomalies of Water.

We perform molecular dynamics simulations in order to study thermodynamics and the structure of supercooled aqueous solutions of lithium chloride (LiCl) at concentrations c = 0.678 and 2.034 mol/kg. We model the solvent using the TIP4P/2005 potential and the ions using the Madrid-2019 force field, a force field particularly suited for studying this solution. We find that, for c = 0.678 mol/kg, the behavior of the equation of state, studied in the P-T plane, indicates the presence of a liquid-liquid phase transition, similar to what was previously found for bulk water. We estimate the position of the liquid-liquid critical point to be at Tc ≈ 174 K, Pc ≈ 1775 bar, and ρc ≈ 1.065 g/cm3. When the concentration is tripled to c = 2.034 mol/kg, no critical point is observed, indicating its possible disappearance at this concentration. We also study the water-water and water-ions structure in the two solutions, and we find that at the concentrations examined the effect of ions on the water-water structure is not strong, and all the features found in bulk water are preserved. We also calculate the hydration number of the Li and Cl ions, and in line with experiments, we find the value of 4 for Li+ and between 5.5 and 6 for Cl-, confirming the good performances of the Madrid-2019 force field.

The therapeutic concordance approach reduces adverse drug reactions in patients with resistant hypertension.

Background: Adverse drug reactions (ADRs) remain among the leading causes of therapy-resistant hypertension (TRH) and uncontrolled blood pressure (BP). We have recently reported beneficial results in BP control in patients with TRH adopting an innovative approach, defined as therapeutic concordance, in which trained physicians and pharmacists reach a concordance with patients to make them more involved in the therapeutic decision-making process. Methods: The main scope of this study was to investigate whether the therapeutic concordance approach could lead to a reduction in ADR occurrence in TRH patients. The study was performed in a large population of hypertensive subjects of the Campania Salute Network in Italy (ClinicalTrials.gov Identifier: NCT02211365). Results: We enrolled 4,943 patients who were firstly followed-up for 77.64 ± 34.44 months, allowing us to identify 564 subjects with TRH. Then, 282 of these patients agreed to participate in an investigation to test the impact of the therapeutic concordance approach on ADRs. At the end of this investigation, which had a follow-up of 91.91 ± 54.7 months, 213 patients (75.5%) remained uncontrolled while 69 patients (24.5%, p < 0.0001) reached an optimal BP control. Strikingly, during the first follow-up, patients had complained of a total of 194 ADRs, with an occurrence rate of 68.1% and the therapeutic concordance approach significantly reduced ADRs to 72 (25.5%). Conclusion: Our findings indicate that the therapeutic concordance approach significantly reduces ADRs in TRH patients.

Therapeutic concordance improves blood pressure control in patients with resistant hypertension.

INTRODUCTION: An empathetic approach may be particularly useful in patients with therapy-resistant hypertension (TRH), defined as the failure to achieve target blood pressure (BP) despite a maximal doses of 3 antihypertensive drugs including a diuretic. However, the effects of therapeutic concordance have not been determined in hypertensive patients. METHODS: We designed a study to explore the impact of therapeutic concordance in patients with TRH, who were included in an intervention arm based on a protocol in which trained personnel periodically verified the pharmacological regimen of these patients. RESULTS: From a cohort of 5331 hypertensive patients followed-up for 77.64 ± 34.44 months, 886 subjects were found to have TRH; of these, 322 had apparent TRH (aTRH: uncontrolled office BP but optimal home BP) and 285 refused to participate in a second follow-up study, yielding a population of 279 patients with true TRH (tTRH). These tTRH patients were followed according to the therapeutic concordance protocol for 91.91 ± 54.7 months, revealing that 210 patients (75.27%) remained with uncontrolled BP (uncontrolled tTRH, Group I) while 69 patients (24.73%) reached an optimal BP control (average BP <140/90 mmHg in at least 50% of follow-up visits, Group II). Strikingly, at the end of the second follow-up, the percentage of patients displaying a decline in kidney function was significantly smaller in Group II than in Group I (8.5% vs 23.4%, p < 0.012). CONCLUSIONS: Taken together, our findings indicate for the first time that therapeutic concordance significantly improves the outcome of antihypertensive treatment in a population of patients with TRH.

Determinants and Characteristics of Insulin Dose Requirements in Children and Adolescents with New-Onset Type 1 Diabetes: Insights from the INSENODIAB Study.

Aims: New-onset type 1 diabetes mellitus (T1D) in pediatric patients represents a clinical challenge for initial total daily insulin dosing (TIDD) due to substantial heterogeneity in practice and lack of consensus on the optimal starting dose. Our INSENODIAB (INsulin SEnsitivity in New Onset type 1 DIABetes) study is aimed at (1) exploring the influence of patient-specific characteristics on insulin requirements in pediatric patients with new-onset T1D; (2) constructing a predictive model for the recommended TIDD tailored to individual patient profiles; and (3) assessing potential associations between TIDD and patient outcomes at follow-up intervals of 3 and 12 months. Methods: We conducted a comprehensive analysis of medical records for children aged 6 months to 18 years, hospitalized for new-onset T1D from 2013 to 2022. The study initially involved multivariable regression analysis on a retrospective cohort (rINSENODIAB), incorporating baseline variables. Subsequently, we validated the model robustness on a prospective cohort (pINSENODIAB) with a significance threshold of 5%. The model accuracy was assessed by Pearson's correlation. Results: Our study encompassed 103 patients in the retrospective cohort and 80 in the prospective cohort, with median TIDD at diagnosis of 1.1 IU/kg BW/day (IQR 0.5). The predictive model for optimal TIDD was established using baseline characteristics, resulting in the following formula: TIDD (IU/d) = ([0.09 × Age2] + [0.68 × %Weight Loss] + [28.60 × Veinous pH] - [1.03 × Veinous bicarbonates] + [0.81 × Weight] - 194.63). Validation of the model using the pINSENODIAB cohort demonstrated a significant Pearson correlation coefficient of 0.74. Notably, no significant correlation was observed between TIDD at diagnosis and partial remission markers (IDAA1C, C-peptide) at 3- and 12-months postdiagnosis time points. Conclusions: In the context of new-onset T1D in pediatric patients, we identified key influencing factors for determining optimal TIDD, including age, percentage of weight loss, weight, veinous pH, and bicarbonates. These findings have paved the way for the development of a dosing algorithm to potentially expedite glycemic control stabilization and facilitate a more individualized approach to treatment regimens.

High HDL (High-Density Lipoprotein) Cholesterol Increases Cardiovascular Risk in Hypertensive Patients.

BACKGROUND: Emerging evidence suggests that elevated circulating levels of HDL-C (high-density lipoprotein cholesterol) could be linked to an increased mortality risk. However, to the best of our knowledge, the relationship between HDL-C and specific cardiovascular events has never been investigated in patients with hypertension. METHODS: To fill this knowledge gap, we analyzed the relationship between HDL-C levels and cardiovascular events in hypertensive patients within the Campania Salute Network in Southern Italy. RESULTS: We studied 11 987 patients with hypertension, who were followed for 25 534 person-years. Our population was divided in 3 groups according to the HDL-C plasma levels: HDL-C<40 mg/dL (low HDL-C); HDL-C between 40 and 80 mg/dL (medium HDL-C); and HDL-C>80 mg/dL (high HDL-C). At the follow-up analysis, adjusting for potential confounders, we observed a total of 245 cardiovascular events with a significantly increased risk of cardiovascular events in the low HDL-C group and in the high HDL-C arm compared with the medium HDL-C group. The spline analysis revealed a nonlinear U-shaped association between HDL-C levels and cardiovascular outcomes. Interestingly, the increased cardiovascular risk associated with high HDL-C was not confirmed in female patients. CONCLUSIONS: Our data demonstrate that there is a U-shaped association between HDL-C and the risk of cardiovascular events in male patients with hypertension.

L-Arginine Enhances the Effects of Cardiac Rehabilitation on Physical Performance: New Insights for Managing Cardiovascular Patients During the COVID-19 Pandemic.

Cardiac rehabilitation (CR) following acute myocardial infarction (AMI) improves physical capacities and decreases hospitalizations and cardiovascular mortality. L-arginine is the substrate used by nitric oxide (NO) synthase to generate NO and it has been shown to exert its beneficial effects on endothelium driving vasodilatation, reducing inflammation, and ameliorating physical function. We hypothesized that L-arginine could enhance physical capacities in patients who underwent CR after AMI. We designed a study aimed to assess the effects of L-arginine administration on the physical capacity of patients who underwent coronary revascularization after AMI. The trial was carried out amid the COVID-19 pandemic. Patients were assigned, with a 2:1 ratio, to add to their standard therapy one bottle containing 1.66 g of L-arginine or one bottle of identical aspect apart from not containing L-arginine, twice a day orally for 3 weeks. Patients performed a 6-minute walking test (6MWT), and their Borg modified 0-10 rating of perceived exertion (BRPE) was assessed before starting and at the end of the treatment. Seventy-five patients receiving L-arginine, and 35 receiving placebo successfully completed the study. The 6MWT distance increased significantly in the L-arginine group compared with both baseline and placebo (P < 0.0001). Additionally, we observed a significant improvement in the BRPE in patients treated with L-arginine but not in the placebo group. Taken together, our data indicate that L-arginine potentiates the response to CR independently of age, sex, baseline functional capacity, and comorbid conditions. SIGNIFICANCE STATEMENT: This study shows for the first time that oral supplementation of L-arginine potentiates the response to cardiac rehabilitation after myocardial infarction and cardiac revascularization. Indeed, we observed a significant improvement in two fundamental parameters, namely, the 6-minute walking test and the Borg modified 0-10 rating of perceived exertion. Strikingly, the beneficial effects of L-arginine were independent of age, sex, comorbid conditions, and baseline functional capacity.

Structure and dynamics of nanoconfined water and aqueous solutions.

This review is devoted to discussing recent progress on the structure, thermodynamic, reactivity, and dynamics of water and aqueous systems confined within different types of nanopores, synthetic and biological. Currently, this is a branch of water science that has attracted enormous attention of researchers from different fields interested to extend the understanding of the anomalous properties of bulk water to the nanoscopic domain. From a fundamental perspective, the interactions of water and solutes with a confining surface dramatically modify the liquid's structure and, consequently, both its thermodynamical and dynamical behaviors, breaking the validity of the classical thermodynamic and phenomenological description of the transport properties of aqueous systems. Additionally, man-made nanopores and porous materials have emerged as promising solutions to challenging problems such as water purification, biosensing, nanofluidic logic and gating, and energy storage and conversion, while aquaporin, ion channels, and nuclear pore complex nanopores regulate many biological functions such as the conduction of water, the generation of action potentials, and the storage of genetic material. In this work, the more recent experimental and molecular simulations advances in this exciting and rapidly evolving field will be reported and critically discussed.

Advances in the study of supercooled water.

In this review, we report recent progress in the field of supercooled water. Due to its uniqueness, water presents numerous anomalies with respect to most simple liquids, showing polyamorphism both in the liquid and in the glassy state. We first describe the thermodynamic scenarios hypothesized for the supercooled region and in particular among them the liquid-liquid critical point scenario that has so far received more experimental evidence. We then review the most recent structural indicators, the two-state model picture of water, and the importance of cooperative effects related to the fact that water is a hydrogen-bonded network liquid. We show throughout the review that water's peculiar properties come into play also when water is in solution, confined, and close to biological molecules. Concerning dynamics, upon mild supercooling water behaves as a fragile glass former following the mode coupling theory, and it turns into a strong glass former upon further cooling. Connections between the slow dynamics and the thermodynamics are discussed. The translational relaxation times of density fluctuations show in fact the fragile-to-strong crossover connected to the thermodynamics arising from the existence of two liquids. When considering also rotations, additional crossovers come to play. Mobility-viscosity decoupling is also discussed in supercooled water and aqueous solutions. Finally, the polyamorphism of glassy water is considered through experimental and simulation results both in bulk and in salty aqueous solutions. Grains and grain boundaries are also discussed.

Dynamical crossover and its connection to the Widom line in supercooled TIP4P/Ice water.

We perform molecular dynamics simulations with the TIP4P/Ice water model to characterize the relationship between dynamics and thermodynamics of liquid water in the supercooled region. We calculate the relevant properties of the phase diagram, and we find that TIP4P/Ice presents a retracing line of density maxima, similar to what was previously found for atomistic water models and models of other tetrahedral liquids. For this model, a liquid-liquid critical point between a high-density liquid and a low-density liquid was recently found. We compute the lines of the maxima of isothermal compressibility and the minima of the coefficient of thermal expansion in the one phase region, and we show that these lines point to the liquid-liquid critical point while collapsing on the Widom line. This line is the line of the maxima of correlation length that emanates from a second order critical point in the one phase region. Supercooled water was found to follow mode coupling theory and to undergo a transition from a fragile to a strong behavior right at the crossing of the Widom line. We find here that this phenomenology also happens for TIP4P/Ice. Our results appear, therefore, to be a general characteristic of supercooled water, which does not depend on the interaction potential used, and they reinforce the idea that the dynamical crossover from a region where the relaxation mechanism is dominated by cage relaxation to a region where cages are frozen and hopping dominates is correlated in water to a phase transition between a high-density liquid and a low-density liquid.

Effect of trehalose on protein cryoprotection: Insights into the mechanism of slowing down of hydration water.

We study, with molecular dynamics simulations, a lysozyme protein immersed in a water-trehalose solution upon cooling. The aim is to understand the cryoprotectant role played by this disaccharide through the modifications that it induces on the slow dynamics of protein hydration water with its presence. The α-relaxation shows a fragile to strong crossover about 20° higher than that in the bulk water phase and 15° higher than that in lysozyme hydration water without trehalose. The protein hydration water without trehalose was found to show a second slower relaxation exhibiting a strong to strong crossover coupled with the protein dynamical transition. This slower relaxation time importantly appears enormously slowed down in our cryoprotectant solution. On the other hand, this long-relaxation in the presence of trehalose is also connected with a stronger damping of the protein structural fluctuations than that found when the protein is in contact with the pure hydration water. Therefore, this appears to be the mechanism through which trehalose manifests its cryoprotecting function.

Protein-Water and Water-Water Long-Time Relaxations in Protein Hydration Water upon Cooling-A Close Look through Density Correlation Functions.

We report results on the translational dynamics of the hydration water of the lysozyme protein upon cooling obtained by means of molecular dynamics simulations. The self van Hove functions and the mean square displacements of hydration water show two different temperature activated relaxation mechanisms, determining two dynamic regimes where transient trapping of the molecules is followed by hopping phenomena to allow to the structural relaxations. The two caging and hopping regimes are different in their nature. The low-temperature hopping regime has a time scale of tenths of nanoseconds and a length scale on the order of 2-3 water shells. This is connected to the nearest-neighbours cage effect and restricted to the supercooling, it is absent at high temperature and it is the mechanism to escape from the cage also present in bulk water. The second hopping regime is active at high temperatures, on the nanoseconds time scale and over distances of nanometers. This regime is connected to water displacements driven by the protein motion and it is observed very clearly at high temperatures and for temperatures higher than the protein dynamical transition. Below this temperature, the suppression of protein fluctuations largely increases the time-scale of the protein-related hopping phenomena at least over 100 ns. These protein-related hopping phenomena permit the detection of translational motions of hydration water molecules longly persistent in the hydration shell of the protein.