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Citrobacter koseri (formerly classified as Citrobacter diversus ) is a gram-negative bacillus (GNB) that occurs as an opportunistic pathogen in neonates and immunocompromised patients. Citrobacter species have been implicated in nosocomial settings leading to infections involving the urinary tract, respiratory tract, liver, biliary tract, meninges, and even in rarer conditions—blood stream infection and infective endocarditis (IE). Gram-negative bacilli are responsible for 3% to 4% of all IE cases and have been traditionally associated with intravenous drug users. Patients with non-HACEK (species other than Haemophilus species, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, or Kinglella species) GNB IE have poor clinical outcomes with higher rates of in-hospital mortality and complications. The American Heart Association (AHA) and Infectious Diseases Society of America (IDSA) both recommend the use of combination antibiotic therapy with a beta-lactam (penicillins, cephalosporins, or carbapenems) and either an aminoglycoside or fluoroquinolones for 6 weeks (about 1 and a half months) to treat IE due to non-HACEK GNB. Citrobacter koseri is becoming more recognized due to its inherent resistance to ampicillin and emerging drug resistance to beta lactams and aminoglycosides requiring carbapenem therapy. Our case is of a 75-year-old male with no previously reported history of primary or secondary immunodeficiency disorders who developed C koseri blood stream infection. His infectious work-up revealed mitral valve IE and septic cerebral emboli resulting in ischemic infarcts. This case illustrates the importance of recognizing GNB organisms as rising human pathogens in IE cases even without active injection drug use or nosocomial exposure.

Background:. Anterior cruciate ligament reconstruction with hamstring tendon autograft (H-ACLR) is a standard ambulatory procedure with the potential for considerable postoperative pain. We hypothesized that general anesthesia combined with a multimodal analgesia regimen would reduce postoperative opioid use associated with H-ACLR. Methods:. This study was a single-center, surgeon-stratified, double-blinded, placebo-controlled, randomized clinical trial. The primary end point was the total postoperative opioid use during the immediate postoperative period, and secondary outcomes included postoperative knee pain, adverse events, and ambulatory discharge efficiency. Results:. One hundred and twelve subjects, 18 to 52 years of age, were randomized to placebo (57 subjects) or combination multimodal analgesia (MA) (55 subjects). The MA group required fewer opioids postoperatively (mean ± standard deviation, 9.81 ± 7.58 versus 13.88 ± 8.49 morphine milligram equivalents; p = 0.010; effect size = −0.51). Similarly, the MA group required fewer opioids within the first 24 hours postoperatively (mean ± standard deviation, 16.56 ± 10.77 versus 22.13 ± 10.66 morphine milligram equivalents; p = 0.008; effect size = −0.52). The subjects in the MA group reported lower posteromedial knee pain (median [interquartile range, IQR]: 3.0 [0.0 to 5.0] versus 4.0 [2.0 to 5.0]; p = 0.027) at 1 hour postoperatively. Nausea medication was required for 10.5% of the subjects receiving the placebo versus 14.5% of the subjects receiving MA (p = 0.577). Pruritis was reported for 17.5% of subjects receiving the placebo versus 14.5% receiving MA (p = 0.798). The median time to discharge was 177 minutes (IQR, 150.5 to 201.0 minutes) for subjects receiving placebo versus 188 minutes (IQR, 160.0 to 222.0 minutes) for those receiving MA (p = 0.271). Conclusions:. A combination of general anesthesia and local, regional, oral, and intravenous multimodal analgesia appears to reduce postoperative opioid requirements after H-ACLR compared with placebo. Adding preoperative patient education and focusing on donor-site analgesia may maximize perioperative outcomes. Level of Evidence:. Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Background: Hamstring tendon (HT) autograft for anterior cruciate ligament (ACL) reconstruction has shown equivalent graft failure rates to bone-patellar-tendon-bone (BTB) with decreased prevalence of anterior knee pain. It should be noted that young athletes, particularly females athletes, may have increased graft failure rates with HT versus BTB. Additionally, HT graft diameters

Odontogenic bacteremia, most commonly involving gram-positive oral flora, can result from daily self-care practices or professional dental procedures. Though usually transient and quickly cleared by the immune system, the presence of periodontal disease increases the frequency of exposure and risk of persistence of oral-systemic infections. Comorbidities such as asplenia, alcoholism, and immunocompromise increase the risk of complications of hematogenous spread and severe systemic illness. Capnocytophaga is a genus of anaerobic fastidious gram-negative bacilli, which is a common member of human oral flora, and its density is proportional to mass of dental plaques and periodontal diseases. Capnocytophaga spp that colonize humans are less virulent and are uncommon causes of bacteremia when compared with the Capnocytophaga typical of canines. C gingivalis has been rarely reported as a cause of disease in immunocompromised or immunocompetent hosts. In this article, we present a case of an immunocompromised 70-year-old man with poor oral hygiene, on methotrexate and prednisone for rheumatoid arthritis and sarcoidosis, who was admitted for chronic obstructive pulmonary disease exacerbation and developed C gingivalis bacteremia and septic shock after an episode of upper gastrointestinal bleeding. Poor oral hygiene in our patient is believed to have increased his risk as an immunocompromised patient to developing C gingivalis bacteremia. This case highlights the importance of oral care in immunocompromised patients especially while hospitalized, and those about to receive transplant, chemotherapy, or on immune modulators.

Objectives:. Coronavirus disease 2019 is associated with high mortality rates and multiple organ damage. There is increasing evidence that these patients are at risk for various cardiovascular insults; however, there are currently no guidelines for the diagnosis and management of such cardiovascular complications in patients with coronavirus disease 2019. We share data and recommendations from a multidisciplinary team to highlight our institution’s clinical experiences and guidelines for managing cardiovascular complications of coronavirus disease 2019. Design, Setting, and Patients:. This was a retrospective cohort study of patients admitted to one of six ICUs dedicated to the care of patients with coronavirus disease 2019 located in three hospitals within one academic medical center in Atlanta, Georgia. Measurements/Interventions:. Chart review was conducted for sociodemographic, laboratory, and clinical data. Rates of specific cardiovascular complications were assessed, and data were analyzed using a chi-square or Wilcoxon rank-sum test for categorical and continuous variables. Additionally, certain cases are presented to demonstrate the sub committee’s recommendations. Main Results:. Two-hundred eighty-eight patients were admitted to the ICU with coronavirus disease 2019. Of these, 86 died (29.9%), 242 (84.03%) had troponin elevation, 70 (24.31%) had dysrhythmias, four (1.39%) had ST-elevation myocardial infarction, eight (2.78%) developed cor pulmonale, and 190 (65.97%) with shock. There was increased mortality risk in patients with greater degrees of troponin elevation (p < 0.001) and with the development of arrhythmias (p < 0.001), cor pulmonale (p < 0.001), and shock (p < 0.001). Conclusions:. While there are guidelines for the diagnosis and management of pulmonary complications of coronavirus disease 2019, there needs to be more information regarding the management of cardiovascular complications as well. These recommendations garnered from the coronavirus disease 2019 cardiology subcommittee from our institution will add to the existing knowledge of these potential cardiovascular insults as well as highlight suggestions for the diagnosis and management of the range of cardiovascular complications of coronavirus disease 2019. Additionally, with the spread of coronavirus disease 2019, our case-based recommendations provide a bedside resource for providers newly caring for patients with coronavirus disease 2019.

Soft tissue infections occur in over 30% of patients with chemotherapy-induced neutropenia. Gram-positive bacterial infections predominate early in neutropenia, and likelihood of infection by resistant bacteria and fungi increases with prolonged neutropenia. Prior infections and exposures influence the risk of rare pathogens. A 55-year-old woman with chemotherapy-induced neutropenia was scratched on her forearm by a dog. She cleaned the wound with isopropanol and was treated empirically with amoxicillin-clavulanate. Over the next 4 days, she developed fever along with erythema, edema, and mild tenderness of the forearm without purulence or crepitus. She was hospitalized and received empiric treatment with intravenous vancomycin, piperacillin-tazobactam, tobramycin, and voriconazole. Despite therapy, her fevers persisted and the cellulitis progressed for over a week. After 10 days of hospitalization, her neutrophil count began to recover and a bulla developed at the wound site. Culture of the bullous fluid grew Serratia marcescens , and antibiotics were switched to cefepime based on susceptibility. She defervesced and showed substantial improvement of cellulitis within 48 hours and was discharged on oral ciprofloxacin. Serratia marcescens skin infections are rare, and this may be the first report of Serratia cellulitis associated with trauma from dog contact. This case highlights the need to consider unusual pathogens based on exposure history and immune status and to obtain cultures from fluid collections or tissue in cases of treatment-resistant soft tissue infections.

Background: Xerostomia is a chief complaint of patients with Sjögren's syndrome (SS). However, newer proposals for SS classification remove xerostomia and hyposalivation from the criteria list. Given these developments and the importance of patient-centered research outcomes, we sought to evaluate the utility of patient-reported xerostomia with implications for classification criteria, and clinical trials targeting SS treatment modalities. Methods: A nested case-control study was designed within The National Institute of Dental and Craniofacial Research/National Institutes of Health (NIDCR/NIH) SS Cohort - one of the largest SS cohorts in the US. Clinical characteristics of those with and without xerostomia in SS and other salivary gland dysfunctions were compared. Several analytical methods were employed, including multivariable logistic regression modeling. Findings: The NIDCR/NIH Sjögren's Syndrome Clinic has an open cohort with ongoing enrollment since 1984. This open cohort comprised of 2046 participants by August 27, 2015. Baseline data of 701 SS, 355 Sicca, and 247 ISS participants within the source cohort were analyzed. Xerostomia was highest among SS participants (87.4%, 95% CI: 84.8%–89.8%) compared to Sicca (72.4%, 95% CI: 67.4%–77.0%, p 3 months (OR: 5.80, 95% CI: 3.62–9.28, p-value 2 (OR: 1.92, 95% CI: 1.20–3.09, p-value = 0.007), and salivary gland swelling (OR: 49.39, 95% CI: 2.02–1206.30, p-value = 0.017). Age, gender, fatigue, pain, anxiety, and autoantibodies were not significantly associated with xerostomia. Interpretation: Findings from this study indicate that patient-reported xerostomia is highly prevalent among SS patients and is associated with several clinical phenotypes of this complex syndrome, thereby making it an important indicator of SS. The evidence also suggests that xerostomia is not limited to low salivary flow but might be reflective of compositional changes of saliva. Consequently, these findings suggest the need to consider xerostomia in the development of SS classification criteria and in patient-centered outcomes research in SS intervention trials. This research was supported by the Intramural Research Program of the National Institutes of Health (NIH), National Institute of Dental and Craniofacial Research (NIDCR) Grant # DE000704-15. Dr. Baer is supported by RO1-DE-12354-15A1.

Background: Parkinson’s disease (PD) patients are prone to infections leading to hospitalization. We used the Norton Scale score (NSS) as a prognostic tool for these patients. Method: Retrospective analysis of consecutive PD patients, all had NSS appreciation upon admission. Analyses were made to establish the association between NSS upon admission, short-term, and long-term clinical outcomes. Results: Five hundred twenty-eight PD patients’ records were reviewed, of which 81 were eligible for analysis. Patients who died during hospitalization had a significantly lower NSS (10.0 vs. 13.1, p = .026). Among surviving patients, those who were discharged to more intensive care facilities relative to their original place of arrival also had a significantly lower NSS (10.38 vs. 13.63, p = .0002). Lower NSS was found to increase the risk for 1-year mortality (odds ratio = 1.3; 95% confidence interval = [1.09, 1.56], p = .003). Conclusion: Lower NSS upon admission of PD patients, suffering from infection is associated with worse clinical outcomes.

Metal carbonates, which are ubiquitous in the near-surface mineral record, are a major product of biomineralizing organisms and serve as important targets for capturing anthropogenic CO 2 emissions. However, pathways of carbonate mineralization typically diverge from classical predictions due to the involvement of disordered precursors, such as the dense liquid phase (DLP), yet little is known about DLP formation or solidification processes. Using in situ methods we report that a highly hydrated bicarbonate DLP forms via liquid-liquid phase separation and transforms into hollow hydrated amorphous CaCO 3 particles. Acidic proteins and polymers extend DLP lifetimes while leaving the pathway and chemistry unchanged. Molecular simulations suggest that the DLP forms via direct condensation of solvated Ca² + ⋅(HCO 3 - ) 2 complexes that react due to proximity effects in the confined DLP droplets. Our findings provide insight into CaCO 3 nucleation that is mediated by liquid-liquid phase separation, advancing the ability to direct carbonate mineralization and elucidating an often-proposed complex pathway of biomineralization., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Bacterial infections have been a serious threat to mankind throughout history. Natural antimicrobial peptides (AMPs) and their membrane disruption mechanism have generated immense interest in the design and development of synthetic mimetics that could overcome the intrinsic drawbacks of AMPs, such as their susceptibility to proteolytic degradation and low bioavailability. Herein, by exploiting the self-assembly and pore-forming capabilities of sequence-defined peptoids, we discovered a family of low-molecular weight peptoid antibiotics that exhibit excellent broad-spectrum activity and high selectivity toward a panel of clinically significant Gram-positive and Gram-negative bacterial strains, including vancomycin-resistant Enterococcus faecalis (VREF), methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus epidermidis (MRSE), Escherichia coli , Pseudomonas aeruginosa , and Klebsiella pneumoniae . Tuning the peptoid side chain chemistry and structure enabled us to tune the efficacy of antimicrobial activity. Mechanistic studies using transmission electron microscopy (TEM), bacterial membrane depolarization and lysis, and time-kill kinetics assays along with molecular dynamics simulations reveal that these peptoids kill both Gram-positive and Gram-negative bacteria through a membrane disruption mechanism. These robust and biocompatible peptoid-based antibiotics can provide a valuable tool for combating emerging drug resistance.

SUCROSE-NON-FERMENTING1-RELATED PROTEIN KINASE1 (SnRK1), a central plant metabolic sensor kinase, phosphorylates its target proteins, triggering a global shift from anabolism to catabolism. Molecular modeling revealed that upon binding of KIN10 to GEMINIVIRUS REP-INTERACTING KINASE1 (GRIK1), KIN10's activation T-loop reorients into GRIK1's active site, enabling its phosphorylation and activation. Trehalose 6-phosphate (T6P) is a proxy for cellular sugar status and a potent inhibitor of SnRK1. T6P binds to KIN10, a SnRK1 catalytic subunit, weakening its affinity for GRIK1. Here, we investigate the molecular details of T6P inhibition of KIN10. Molecular dynamics simulations and in vitro phosphorylation assays identified and validated the T6P binding site on KIN10. Under high-sugar conditions, T6P binds to KIN10, blocking the reorientation of its activation loop and preventing its phosphorylation and activation by GRIK1. Under these conditions, SnRK1 maintains only basal activity levels, minimizing phosphorylation of its target proteins, thereby facilitating a general shift from catabolism to anabolism.

Two-dimensional (2D) materials have attracted intense interest due to their potential for applications in fields ranging from chemical sensing to catalysis, energy storage, and biomedicine. Recently, peptoids, a class of biomimetic sequence-defined polymers, have been found to self-assemble into 2D crystalline sheets that exhibit unusual properties, such as high chemical stability and the ability to self-repair. The structure of a peptoid is close to that of a peptide except that the side chains are appended to the amide nitrogen rather than the α carbon. In this study, we investigated the effect of peptoid sequence on the mechanism and kinetics of 2D assembly on mica surfaces using in situ AFM and time-resolved X-ray scattering. We explored three distinct peptoid sequences that are amphiphilic in nature with hydrophobic and hydrophilic blocks and are known to self-assemble into 2D sheets. The results show that their assembly on mica starts with deposition of aggregates that spread to establish 2D islands, which then grow by attachment of peptoids, either monomers or unresolvable small oligomers, following well-known laws of crystal step advancement. Extraction of the solubility and kinetic coefficient from the dependence of the growth rate on peptoid concentration reveals striking differences between the sequences. The sequence with the slowest growth rate in bulk and with the highest solubility shows almost no detachment; i.e., once a growth unit attaches to the island edge, there is almost no probability of detaching. Furthermore, a peptoid sequence with a hydrophobic tail conjugated to the final carboxyl residue in the hydrophilic block has enhanced hydrophobic interactions and exhibits rapid assembly both in the bulk and on mica. These assembly outcomes suggest that, while the π-π interactions between adjacent hydrophobic blocks play a major role in peptoid assembly, sequence details, particularly the location of charged groups, as well as interaction with the underlying substrate can significantly alter the thermodynamic stability and assembly kinetics.

Multiple jobholding is increasingly common, particularly among full-time employees who have adopted side-hustles -income-generating work from the gig economy that is performed alongside full-time work. A distinguishing feature of side-hustles is substantial autonomy in the work's timing, location, and method. This autonomy has typically been portrayed as beneficial. We shift this consensus by developing a within-person model that suggests elevated side-hustle autonomy-relative to what is typical for that person-sets the employee on a course to feel "boxed in" by their full-time job. Drawing on psychological reactance theory, we argue that elevated autonomy in a side-hustle sensitizes employees to threats that restrict their control. As these employees shift to full-time work, we theorize that this sensitivity is associated with feelings of hostility that contribute to counterproductive behavior. We also propose, however, that side-hustle autonomy has benefits for full-time work-motivating employees to reassert control through increased initiative, thereby enhancing task performance. We explore the countervailing relationships between side-hustle autonomy and full-time work outcomes with a daily experience sampling study (ESM) of 101 full-time employees with side-hustles and their coworkers (Study 1) and a weekly ESM study of 100 full-time employees with side-hustles (Study 2). Taken together, we build and test theory about how employees' side-hustle autonomy exhibits within-person relationships that are a "mixed-bag" for their full-time work behavior. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Peptoids (N-substituted glycines) are a class of biomimetic polymers that have attracted significant attention due to their accessible synthesis and enzymatic and thermal stability relative to their naturally occurring counterparts (polypeptides). While these polymers provide the promise of more robust functional materials via hierarchical approaches, they present a new challenge for computational structure prediction for material design. The reliability of calculations hinges on the accuracy of interactions represented in the force field used to model peptoids. For proteins, structure prediction based on sequence and de novo design has made dramatic progress in recent years; however, these models are not readily transferable for peptoids. Current efforts to develop and implement peptoid-specific force fields are spread out, leading to replicated efforts and a fragmented collection of parameterized sidechains. Here, we developed a peptoid-specific force field containing 70 different side chains, using GAFF2 as starting point. The new model is validated based on the generation of Ramachandran-like plots from DFT optimization compared against force field reproduced potential energy and free energy surfaces as well as the reproduction of equilibrium cis/trans values for some residues experimentally known to form helical structures. Equilibrium cis/trans distributions (Kct) are estimated for all parameterized residues to identify which residues have an intrinsic propensity for cis or trans states in the monomeric state.

Models of trust have focused on the notion that an employee's trust in a coworker is based on that coworker's trustworthiness and the employee's trust propensity-a generalized tendency to believe others are trustworthy. Although these models capture the general assessment of risk associated with trusting a particular coworker, they provide insufficient insight into why an employee might take the risk associated with trust on a particular day. Bringing the concept of risk propensity -the tendency to accept or avoid risk-from the decision-making literature into the trust literature, we build a model of trust that suggests employees' trusting behaviors stem from both their calculated assessment of risk (encapsulated in trustworthiness and trust propensity) and their tendency to take those risks. We draw on motivated reasoning theory (Kunda, 1990) and the decision-making literature to suggest that employees' daily strivings for achievement, affiliation, stimulation, and security induce a biased reasoning process that influences employees' risk propensity that day. Our test of this theoretical model demonstrates that generalized work motives have an indirect effect on employees' trust in their coworkers, through risk propensity, that goes above and beyond established bases of trust. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The surge of opportunities available through the gig economy has increased the sizeable population of people who hold multiple jobs. Many of these multiple jobholders are full-time employees who have adopted side-hustles-income-generating work performed alongside full-time work. A core and ubiquitous feature of both full-time work and side-hustles is status, or membership in a social hierarchy. Although status has traditionally been investigated as an employee's enduring position in the social hierarchy at their full-time job, employees with side-hustles hold two distinct work-related statuses: status in their full-time job and status in their side-hustle. Having two statuses necessarily creates a situation in which employees' status is either consistent or inconsistent across roles. We investigate the implications of status inconsistency between side-hustles and full-time work for employees' stress, well-being, and performance. We assert that status inconsistency between side-hustles and full-time work requires employees to navigate stress-inducing tensions, such as incongruent role expectations and confusion regarding their sense of self. By extension, we propose that status inconsistency between side-hustles and full-time work promotes more role stress than occupying consistently low-status roles. In a four-wave field study of full-time employees with side-hustles, and their supervisors, we use polynomial regression analysis to test our predictions. We find that status inconsistency diminishes performance in full-time work via role stress and emotional exhaustion. Given the burgeoning gig economy and associated changes to how work is organized, our research has important and timely implications for multiple jobholders and their full-time work organizations. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Objective: Sjögren syndrome (SS) has a significant impact on health-related quality of life (HRQOL). We sought to evaluate how the Patient Reported Outcome Measurement Information System (PROMIS) domains in SS may supplement the European League Against Rheumatism (EULAR) Sjögren Syndrome Patient Reported Index (ESSPRI)., Methods: A cross-sectional evaluation was performed on consecutive adult patients during visits to an SS clinic between March 2018 and February 2020. Each patient completed PROMIS short forms related to HRQOL and the ESSPRI, and had a clinical assessment. Patients were either classified as SS by 2016 American College of Rheumatology (ACR)/EULAR criteria, or as "sicca not otherwise specified (NOS)" and used as a comparison group. Univariable and multivariable linear regression models were used to evaluate predictors of PROMIS fatigue (-F), pain interference (-PI), and ability to participate in social roles and activities (-APS)., Results: Two hundred twenty-seven patients with SS and 85 with sicca NOS were included and did not differ in ESSPRI domains; 26% of the SS and 20% of the sicca NOS group had concurrent autoimmune disease. In SS, PROMIS-PI, PROMIS-F, and PROMIS physical function were at least one-half SD worse than US population normative values. PROMIS-PI ( r = 0.73) and PROMIS-F ( r = 0.80) were highly correlated with ESSPRI pain and fatigue subdomains. Fatigue and pain interference, but not dryness or mood disturbance, were the strongest predictors of social participation in multivariable analysis., Conclusion: In our SS cohort, PROMIS instruments identified a high disease burden of pain interference, fatigue, and physical function. PROMIS-F strongly predicted PROMIS-APS. PROMIS-PI and PROMIS-F scores correlated highly with their respective ESSPRI domains. PROMIS instruments should be considered to identify relevant HRQOL patterns in SS., (Copyright © 2022 The Journal of Rheumatology.)

Plant plastidial acyl-acyl carrier protein (ACP) desaturases are a soluble class of diiron-containing enzymes that are distinct from the diiron-containing integral membrane desaturases found in plants and other organisms. The archetype of this class is the stearoyl-ACP desaturase which converts stearoyl-ACP into oleoyl (18:1Δ9cis)-ACP. Several variants expressing distinct regioselectivity have been described including a Δ6-16:0-ACP desaturase from black-eyed Susan vine (Thunbergia alata). We solved a crystal structure of the T. alata desaturase at 2.05 Å resolution. Using molecular dynamics (MD) simulations, we identified a low-energy complex between 16:0-ACP and the desaturase that would position C6 and C7 of the acyl chain adjacent to the diiron active site. The model complex was used to identify mutant variants that could convert the T. alata Δ6 desaturase to Δ9 regioselectivity. Additional modeling between ACP and the mutant variants confirmed the predicted regioselectivity. To validate the in-silico predictions, we synthesized two variants of the T. alata desaturase and analyzed their reaction products using gas chromatography-coupled mass spectrometry. Assay results confirmed that mutants designed to convert T. alata Δ6 to Δ9 selectivity exhibited the predicted changes. In complementary experiments, variants of the castor desaturase designed to convert Δ9 to Δ6 selectivity lost some of their Δ9 desaturation ability and gained the ability to desaturate at the Δ6 position. The computational workflow for revealing the mechanistic understanding of regioselectivity presented herein lays a foundation for designing acyl-ACP desaturases with novel selectivities to increase the diversity of monoenes available for bioproduct applications., (Published by Oxford University Press on behalf of American Society of Plant Biologists 2021. This work is written by US Government employees and is in the public domain in the US.)

Identification of molecules and elucidation of their chemical structure are ubiquitous problems in chemistry. Mass spectrometry (MS) can be used due to its sensitivity and versatility. For detection to occur, analytes must be ionized and transferred to the gas phase. Soft ionization processes such as electrospray ionization are popular; however, resulting microsolvated phases can alter the chemistry of analytes and therefore detection and identification. To understand these processes, we use computational methods to probe the ionization propensity of serine in the gas phase, aqueous microsolvated clusters, and aqueous solution. We show that the tautomeric form of serine is altered by the presence of water, as five water molecules can stabilize the zwitterionic tautomer. Inclusion of cosolutes such as ions can stabilize the zwitterion with as few as one or two water molecules present. We demonstrate that ionization propensity, as measured by gas phase bacisity, can increase by over 100 kJ/mol when placed in a small water-serine cluster, showing the sensitivity of the chemistry of microsolvated analytes. Finally, detailed analysis reveals that small droplets (less than seven water molecules) are extremely sensitive to addition of further water molecules. Beyond this limit, structural and electronic properties change little with droplet size.

Research indicates that whereas ingratiation directed toward one's supervisor enhances employee-supervisor social exchange quality, it diminishes social exchange quality with those who observe this behavior, such as team members. However, because researchers have largely overlooked the role of social context in shaping supervisors' and teammates' reactions to ingratiatory employees, current understanding of how ingratiation plays out in complex organizational settings may be incomplete, and perhaps misleading. In this study, we augment a social context perspective with social exchange theory to propose that comparative levels of ingratiation, determined by the focal employee's ingratiation in the context of other team members' ingratiation, shape social exchange quality with supervisors and teammates. The results from a multi-wave multi-source field study of 222 employees and their supervisors from 64 teams show that higher levels of ingratiation relative to other team members increases the employee's social exchange quality with the supervisor, whereas congruence between the employee's and other team members' ingratiation enhances social exchange quality with team members. We also find that relative ingratiation and ingratiation congruence increase citizenship received from supervisors and team members, respectively, via social exchange quality with the corresponding actor(s). Overall, our research contributes to a more complete understanding of ingratiation, especially in regard to how reactions to this behavior are largely a function of the social context in which it occurs. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The binding of group II metal cations such as Ca 2+ and Mg 2+ has been largely categorized as electrostatic or ionic using carboxylate symmetric and asymmetric stretching frequency assignments that have been historically used with little regard for the solvation environment of aqueous solutions. However, given the importance of these cations and their binding mechanisms related to biological function and in revealing surface enrichment factors for ocean to marine aerosol transfer, it is imperative that a deeper understanding be sought to include hydration effects. Here, infrared reflection-absorption and Raman spectra for surface and solution phase carboxylate binding information, respectively, are compared against bare (unbound) carboxylate and bidentate Zn 2+ :carboxylate spectral signatures. Spectral non-coincidence effect analysis, temperature studies, and spectral and potential of mean force calculations result in a concise interpretation of binding motifs that include the role of mediating water molecules, that is, contact and solvent-shared ion pairs. Calcium directly binds to the carboxylate group in contact ion pairs where magnesium rarely does. Moreover, we reveal the dominance of the solvent-shared ion pair of magnesium with carboxylate at the air-water interface and in solution.

The plant acyl-acyl carrier protein (ACP) desaturases are a family of soluble enzymes that convert saturated fatty acyl-ACPs into their cis-monounsaturated equivalents in an oxygen-dependent reaction. These enzymes play a key role in biosynthesis of monounsaturated fatty acids in plants. ACPs are central proteins in fatty acid biosynthesis that deliver acyl chains to desaturases. They have been reported to show a varying degree of local dynamics and structural variability depending on the acyl chain size. It has been suggested that substrate-specific changes in ACP structure and dynamics have a crucial impact on the desaturase enzymatic activity. Using molecular dynamics simulations, we investigated the intrinsic solution structure and dynamics of ACP from spinach with four different acyl chains: capric (C 10 ), myristic (C 14 ), palmitic (C 16 ), and stearic (C 18 ) acids. We found that the fatty acids can adopt two distinct structural binding motifs, which feature different binding free energies and influence the ACP dynamics in a different manner. Docking simulations of ACP to castor Δ 9 -desaturase and ivy Δ 4 -desaturase suggest that ACP desaturase interactions could lead to a preferential selection between the motifs., (Copyright © 2021 Biophysical Society. All rights reserved.)

Fully synthetic peptoid membranes are known to mimic important features of biological membranes, with several advantages over other biomimetic membranes. A fundamental understanding of how the individual peptoid amphiphiles assemble in solution to form the bilayer membrane is key to unlocking their versatility for application in a broad range of processes. In this study, in situ X-ray scattering and molecular dynamics simulations are used to understand the early stages of assembly of three different peptoids that exhibit distinctly different crystallization kinetics. The in situ measurements reveal that the peptoids aggregate first into a nascent phase that is less crystalline than the assembled peptoid membrane. Anisotropic aromatic interactions are determined to be the dominant driving force in the early stages of membrane formation. These results provide key insights into how the peptoid assembly may be manipulated during the early stages of assembly and nucleation and growth.

Objective: To define the association between oral and systemic manifestations of Sjögren syndrome (SS) and quality of life (QOL)., Methods: We analyzed a cross-sectional survey conducted by the Sjögren's Foundation in 2016, with 2961 eligible responses. We defined oral symptom and sign exposures as parotid gland swelling, dry mouth, mouth ulcers/sores, oral candidiasis, trouble speaking, choking or dysphagia, sialolithiasis or gland infection, and dental caries. Systemic exposures included interstitial lung disease, purpura/petechiae/cryoglobulinemia, vasculitis, neuropathy, leukopenia, interstitial nephritis, renal tubular acidosis, autoimmune hepatitis, primary biliary cholangitis, or lymphoma. Outcomes included SS-specific QOL questions generated by SS experts and patients., Results: Using multivariable regression models adjusted for age, sex, race, and employment, we observed that mouth ulcers or sores, trouble speaking, and dysphagia were associated with poor quality of life. The following oral aspects had the greatest effect on the following QOL areas: (1) mouth ulcers/sores on the challenge and burden of living with SS (OR 4.26, 95% CI 2.89-6.28); (2) trouble speaking on memory and concentration (OR 4.24, 95% CI 3.28-5.48); and (3) dysphagia on functional interference (OR 4.25, 95% CI 3.13-5.79). In contrast, systemic manifestations were associated with QOL to a lesser extent or not at all., Conclusion: Oral manifestations of SS, particularly mouth ulcers or sores, trouble speaking, and dysphagia, were strongly associated with worse QOL. Further study and targeted treatment of these oral manifestations provides the opportunity to improve quality of life in patients with SS., (Copyright © 2021 by the Journal of Rheumatology.)

We study the prototypical S N 2 reaction Cl - + CH 3 Cl → CH 3 Cl + Cl - in water using quantum mechanics/molecular mechanics (QM/MM) computer simulations with transition path sampling and inertial likelihood maximization. We have identified a new solvent coordinate to complement the original atom-exchange coordinate used in the classic analysis by Chandrasekhar, Smith, and Jorgensen [J. Am. Chem. Soc. 107, 154 (1985)]. The new solvent coordinate quantifies instantaneous solvent-induced polarization relative to the equilibrium average charge density at each point along the reaction pathway. On the basis of likelihood scores and committor distributions, the new solvent coordinate improves upon the description of solvent dynamical effects relative to previously proposed solvent coordinates. However, it does not increase the transmission coefficient or the accuracy of a transition state theory rate calculation.

Rate theories have found great utility across the chemical sciences by providing a physically transparent way to analyze dynamical processes. Here we demonstrate the benefits of using transition state theory and Marcus theory to study the rate of proton transfer in HCl solutions. By using long ab initio molecular dynamics simulations, we show that good agreement is obtained between these two different formulations of rate theory and how they can be used to study the pathways and lifetime of proton transfer in aqueous solution. Since both rate theory formulations utilize identical sets of molecular data, this provides a self-consistent theoretical picture of the rates of aqueous phase proton transfer. Specifically, we isolate and quantify the rates of proton transfer, ion-pair dissociation, and solvent exchange in concentrated HCl solutions. Our analysis predicts a concentration dependence to both proton transfer and ion-pairing. Moreover, our estimate of the lifetime for the Zundel species is 0.8 and 1.3 ps for 2 M and 8 M HCl, respectively. We demonstrate that concentration effects can indeed be quantified through the combination of state-of-the-art simulation and theory and provides a picture of the important correlations between the cation (hydronium) and the counterion in acid solutions.

The ability to reproduce the experimental structure of water around the sodium and potassium ions is a key test of the quality of interaction potentials due to the central importance of these ions in a wide range of important phenomena. Here, we simulate the Na + and K + ions in bulk water using three density functional theory functionals: (1) the generalized gradient approximation (GGA) based dispersion corrected revised Perdew, Burke, and Ernzerhof functional (revPBE-D3) (2) the recently developed strongly constrained and appropriately normed (SCAN) functional (3) the random phase approximation (RPA) functional for potassium. We compare with experimental X-ray diffraction (XRD) and X-ray absorption fine structure (EXAFS) measurements to demonstrate that SCAN accurately reproduces key structural details of the hydration structure around the sodium and potassium cations, whereas revPBE-D3 fails to do so. However, we show that SCAN provides a worse description of pure water in comparison with revPBE-D3. RPA also shows an improvement for K + , but slow convergence prevents rigorous comparison. Finally, we analyse cluster energetics to show SCAN and RPA have smaller fluctuations of the mean error of ion-water cluster binding energies compared with revPBE-D3.

When hydrolyzable cations such as aluminum interact with solid-water interfaces, macroscopic interfacial properties ( e.g ., surface charge and potential) and interfacial phenomena ( e.g ., particle adhesion) become tightly linked with the microscopic details of ion adsorption and speciation. We use in situ atomic force microscopy to directly image individual aluminum ions at a mica-water interface and show how adsorbate populations change with pH and aluminum activity. Complementary streaming potential measurements then allow us to build a triple layer model (TLM) that links surface potentials to adsorbate populations, via equilibrium binding constants. Our model predicts that hydrolyzed species dominate the mica-water interface, even when unhydrolyzed species dominate the solution. Ab initio molecular dynamics (AIMD) simulations confirm that aluminum hydrolysis is strongly promoted at the interface. The TLM indicates that hydrolyzed adsorbates are responsible for surface-potential inversions, and we find strong correlations between hydrolyzed adsorbates and particle-adhesion forces, suggesting that these species mediate adhesion by chemical bridging.

An unintended side effect of the goal-setting literature's focus on cognitive dynamics has been an insufficient acknowledgment of how employees affectively experience high-performance goals. This is potentially a crucial oversight, considering the substantial body of research that has demonstrated the impact of employees' affective states on organizationally relevant attitudes and behaviors. Drawing on cognitive-motivational-relational theory (Lazarus, 1991), we explore the discrete affective states elicited by high-performance goals. We suggest that a key to understanding these affective states is the source of the performance goal. The literature has largely considered whether goals are organization-set or self-set to be a peripheral aspect of a goal's impact on employees. From an affective perspective, however, an employee's self-set performance goals may be appraised and experienced quite differently than performance goals assigned by the organization. We build a theoretical model that suggests high organization-set goals will elicit anxiety due to an appraisal characterized by uncertainty and threat, whereas high self-set goals will elicit enthusiasm due to an appraisal characterized by positive expectations and benefit. We propose that these affective states will have diverging effects on employees' emotional exhaustion and, subsequently, their extrarole performance. We support our model both in the field via a 4-wave study conducted with police officers and their supervisors and in the laboratory via an experiment in which we manipulated goal source during a performance task. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

We exploit gas-phase cluster ion techniques to provide insight into the local interactions underlying divalent metal ion-driven changes in the spectra of carboxylic acids at the air-water interface. This information clarifies the experimental findings that the CO stretching bands of long-chain acids appear at very similar energies when the head group is deprotonated by high subphase pH or exposed to relatively high concentrations of Ca 2+ metal ions. To this end, we report the evolution of the vibrational spectra of size-selected [Ca 2+ ·RCO 2 - ] + ·(H 2 O) n =0 to 12 and RCO 2 - ·(H 2 O) n =0 to 14 cluster ions toward the features observed at the air-water interface. Surprisingly, not only does stepwise hydration of the RCO 2 - anion and the [Ca 2+ ·RCO 2 - ] + contact ion pair yield solvatochromic responses in opposite directions, but in both cases, the responses of the 2 (symmetric and asymmetric stretching) CO bands to hydration are opposite to each other. The result is that both CO bands evolve toward their interfacial asymptotes from opposite directions. Simulations of the [Ca 2+ ·RCO 2 - ] + ·(H 2 O) n clusters indicate that the metal ion remains directly bound to the head group in a contact ion pair motif as the asymmetric CO stretch converges at the interfacial value by n = 12. This establishes that direct metal complexation or deprotonation can account for the interfacial behavior. We discuss these effects in the context of a model that invokes the water network-dependent local electric field along the C-C bond that connects the head group to the hydrocarbon tail as the key microscopic parameter that is correlated with the observed trends., Competing Interests: The authors declare no conflict of interest.

Many biological systems are composed of nanoscale structures having hydrophobic and hydrophilic groups adjacent to one another and in contact with aqueous electrolyte solution. The interaction of ions with such structures is of fundamental importance. Although many studies have focused on characterizing planar extended (often air/water) interfaces, little is known about ion speciation at complex nanoscale biological systems. To start understanding the complex mechanisms involved, we use a hexadecane nanodroplet system, stabilized with a dilute monolayer of positively charged dodecyltrimethylammonium cations (DTA + ) groups in contact with an electrolyte solution (NaSCN). Using vibrational sum frequency scattering, second harmonic scattering, ζ-potential measurements, and quantum density functional theory, we find DTA + -SCN - ion pairing at concentrations as low as 5 mM. A variety of ion species emerge at different ionic strengths, with differently oriented SCN - groups adsorbed on hydrophilic or hydrophobic parts of the surface. This diverse and heterogeneous chemical environment is surprisingly different from the behavior at extended liquid planar interfaces, where ion pairing is typically detected at molar concentrations and nanoscale system stability is no requirement.

Muscovite mica (001) is a widely used model surface for controlling molecular assembly and a common substrate for environmental adsorption processes. The mica (001) surface displays near-trigonal symmetry, but many molecular adsorbates-including water-exhibit unequal probabilities of alignment along its three nominally equivalent lattice directions. Buried hydroxyl groups within the muscovite structure are speculated to be responsible, but direct evidence is lacking. Here, we utilize vibrational sum frequency generation spectroscopy (vSFG) to characterize the orientation and hydrogen-bonding environment of near-surface hydroxyls inside mica. Multiple distinct peaks are detected in the O-H stretch region, which we attribute to Si/Al substitution in the SiO 4 tetrahedron and K + ion adsorption above the hydroxyls based on density functional theory simulations. Our findings demonstrate that vSFG can identify the absolute orientation of -OH groups and, hence, the surface termination at a mica surface, providing a means to investigate how -OH groups influence molecular adsorption and better understand mica stacking-sequences and physical behavior.

The surface tension of dilute salt water is a fundamental property that is crucial to understanding the complexity of many aqueous phase processes. Small ions are known to be repelled from the air-water surface leading to an increase in the surface tension in accordance with the Gibbs adsorption isotherm. The Jones-Ray effect refers to the observation that at extremely low salt concentration, the surface tension decreases. Determining the mechanism that is responsible for this Jones-Ray effect is important for theoretically predicting the distribution of ions near surfaces. Here we use both experimental surface tension measurements and numerical solution of the Poisson-Boltzmann equation to demonstrate that very low concentrations of surfactant in water create a Jones-Ray effect. We also demonstrate that the low concentrations of the surfactant necessary to create the Jones-Ray effect are too small to be detectable by surface sensitive spectroscopic measurements. The effect of surface curvature on this behavior is also examined, and the implications for unexplained bubble phenomena are discussed. This work suggests that the purity standards for water may be inadequate and that the interactions between ions with background impurities are important to incorporate into our understanding of the driving forces that give rise to the speciation of ions at interfaces.

The tetra-phenyl arsonium and tetra-phenyl borate (TATB) assumption is a commonly used extra-thermodynamic assumption that allows single ion free energies to be split into cationic and anionic contributions. The assumption is that the values for the TATB salt can be divided equally. This is justified by arguing that these large hydrophobic ions will cause a symmetric response in water. Experimental and classical simulation work has raised potential flaws with this assumption, indicating that hydrogen bonding with the phenyl ring may favor the solvation of the TB - anion. Here, we perform ab initio molecular dynamics simulations of these ions in bulk water demonstrating that there are significant structural differences. We quantify our findings by reproducing the experimentally observed vibrational shift for the TB - anion and confirm that this is associated with hydrogen bonding with the phenyl rings. Finally, we demonstrate that this results in a substantial energetic preference of the water to solvate the anion. Our results suggest that the validity of the TATB assumption, which is still widely used today, should be reconsidered experimentally in order to properly reference single ion solvation free energy, enthalpy, and entropy.

Understanding the nature of ionic hydration at a fundamental level has eluded scientists despite intense interest for nearly a century. In particular, the microscopic origins of the asymmetry of ion solvation thermodynamics with respect to the sign of the ionic charge remains a mystery. Here, we determine the response of accurate quantum mechanical water models to strong nanoscale solvation forces arising from excluded volumes and ionic electrostatic fields. This is compared to the predictions of two important limiting classes of classical models of water with fixed point changes, differing in their treatment of "lone pair" electrons. Using the quantum water model as our standard of accuracy, we find that a single fixed classical treatment of lone pair electrons cannot accurately describe solvation of both apolar and cationic solutes, emphasizing the need for a more flexible description of local electronic effects in solvation processes. However, we explicitly show that all water models studied respond to weak long-ranged electrostatic perturbations in a manner that follows macroscopic dielectric continuum models, as would be expected. We emphasize the importance of these findings in the context of realistic ion models, using density functional theory and empirical models, and discuss the implications of our results for quantitatively accurate reduced descriptions of solvation in dielectric media.

Peptoids are peptide-mimetic biopolymers that are easy to synthesize and adaptable for use in drugs, chemical scaffolds, and coatings. However, there is insufficient information about their structural preferences and interactions with the environment in various applications. We conducted a study to understand the fundamental differences between peptides and peptoids using molecular dynamics simulations with semiempirical (PM6) and empirical (AMBER) potentials, in conjunction with metadynamics enhanced sampling. From studies of single molecules in water and on surfaces, we found that sarcosine (model peptoid) is much more flexible than alanine (model peptide) in different environments. However, the sarcosine and alanine interact similarly with a hydrophobic or a hydrophilic. Finally, this study highlights the conformational landscape of peptoids and the dominant interactions that drive peptoids toward these conformations.

Mechanisms of CaCO 3 nucleation from solutions that depend on multistage pathways and the existence of species far more complex than simple ions or ion pairs have recently been proposed. Herein, we provide a tightly coupled theoretical and experimental study on the pathways that precede the initial stages of CaCO 3 nucleation. Starting from molecular simulations, we succeed in correctly predicting bulk thermodynamic quantities and experimental data, including equilibrium constants, titration curves, and detailed x-ray absorption spectra taken from the supersaturated CaCO 3 solutions. The picture that emerges is in complete agreement with classical views of cluster populations in which ions and ion pairs dominate, with the concomitant free energy landscapes following classical nucleation theory.

[Correction Notice: An Erratum for this article was reported in Vol 103(1) of Journal of Applied Psychology (see record 2017-44052-001). In the article, the fit statistics in Study 3 were reported in error. The fit of the measurement model is: Χ²(362) = 563.66, p = .001; CFI = .94; SRMR = .05; RMSEA = .04. The fit of the SEM model is: Χ²(362) = 563.66, p = .001; CFI = .94; SRMR = .05; RMSEA = .04.] Workplace cheating behavior is unethical behavior that seeks to create an unfair advantage and enhance benefits for the actor. Although cheating is clearly unwanted behavior within organizations, organizations may unknowingly increase cheating as a byproduct of their pursuit of high performance. We theorize that as organizations place a strong emphasis on high levels of performance, they may also enhance employees' self-interested motives and need for self-protection. We suggest that demands for high performance may elicit performance pressure-the subjective experience that employees must raise their performance efforts or face significant consequences. Employees' perception of the need to raise performance paired with the potential for negative consequences is threatening and heightens self-protection needs. Driven by self-protection, employees experience anger and heightened self-serving cognitions, which motivate cheating behavior. A multistudy approach was used to test our predictions. Study 1 developed and provided validity evidence for a measure of cheating behavior. Studies 2 and 3 tested our predictions in time-separated field studies. Results from Study 2 demonstrated that anger mediates the effects of performance pressure on cheating behavior. Study 3 replicated the Study 2 findings, and extended them to show that self-serving cognitions also mediate the effects of performance pressure on cheating behavior. Implications of our findings for theory and practice are provided. (PsycINFO Database Record, ((c) 2018 APA, all rights reserved).)

Determining the solvation free energies of single ions in water is one of the most fundamental problems in physical chemistry and yet many unresolved questions remain. In particular, the ability to decompose the solvation free energy into simple and intuitive contributions will have important implications for models of electrolyte solution. Here, we provide definitions of the various types of single ion solvation free energies based on different simulation protocols. We calculate solvation free energies of charged hard spheres using density functional theory interaction potentials with molecular dynamics simulation and isolate the effects of charge and cavitation, comparing to the Born (linear response) model. We show that using uncorrected Ewald summation leads to unphysical values for the single ion solvation free energy and that charging free energies for cations are approximately linear as a function of charge but that there is a small non-linearity for small anions. The charge hydration asymmetry for hard spheres, determined with quantum mechanics, is much larger than for the analogous real ions. This suggests that real ions, particularly anions, are significantly more complex than simple charged hard spheres, a commonly employed representation.

Single ion solvation free energies are one of the most important properties of electrolyte solutions and yet there is ongoing debate about what these values are. Only the values for neutral ion pairs are known. Here, we use DFT interaction potentials with molecular dynamics simulation (DFT-MD) combined with a modified version of the quasi-chemical theory (QCT) to calculate these energies for the lithium and fluoride ions. A method to correct for the error in the DFT functional is developed and very good agreement with the experimental value for the lithium fluoride pair is obtained. Moreover, this method partitions the energies into physically intuitive terms such as surface potential, cavity and charging energies which are amenable to descriptions with reduced models. Our research suggests that lithium's solvation free energy is dominated by the free energetics of a charged hard sphere, whereas fluoride exhibits significant quantum mechanical behavior that cannot be simply described with a reduced model.

We present a theory for ion pair dissociation and association, motivated by the concepts of Marcus theory of electron transfer. Despite the extensive research on ion-pairing in many chemical and biological processes, much can be learned from the exploration of collective reaction coordinates. To this end, we explore two reaction coordinates, ion pair distance and coordination number. The study of the correlation between these reaction coordinates provides a new insight into the mechanism and kinetics of ion pair dissociation and association in water. The potential of mean force on these 2D surfaces computed from molecular dynamics simulations of different monovalent ion pairs reveal a Marcus-like mechanism for ion-pairing: Water molecules rearrange forming an activated coordination state prior to ion pair dissociation or association, followed by relaxation of the coordination state due to further water rearrangement. Like Marcus theory, we find the existence of an inverted region where the transition rates are slower with increasing exergonicity. This study provides a new perspective for the future investigations of ion-pairing and transport.

Two-step nucleation pathways in which disordered, amorphous, or dense liquid states precede the appearance of crystalline phases have been reported for a wide range of materials, but the dynamics of such pathways are poorly understood. Moreover, whether these pathways are general features of crystallizing systems or a consequence of system-specific structural details that select for direct versus two-step processes is unknown. Using atomic force microscopy to directly observe crystallization of sequence-defined polymers, we show that crystallization pathways are indeed sequence dependent. When a short hydrophobic region is added to a sequence that directly forms crystalline particles, crystallization instead follows a two-step pathway that begins with the creation of disordered clusters of 10-20 molecules and is characterized by highly non-linear crystallization kinetics in which clusters transform into ordered structures that then enter the growth phase. The results shed new light on non-classical crystallization mechanisms and have implications for the design of self-assembling polymer systems.

First principles molecular dynamics simulation protocol is established using revised functional of Perdew-Burke-Ernzerhof (revPBE) in conjunction with Grimme's third generation of dispersion (D3) correction to describe the properties of water at ambient conditions. This study also demonstrates the consistency of the structure of water across both isobaric (NpT) and isothermal (NVT) ensembles. Going beyond the standard structural benchmarks for liquid water, we compute properties that are connected to both local structure and mass density fluctuations that are related to concepts of solvation and hydrophobicity. We directly compare our revPBE results to the Becke-Lee-Yang-Parr (BLYP) plus Grimme dispersion corrections (D2) and both the empirical fixed charged model (SPC/E) and many body interaction potential model (MB-pol) to further our understanding of how the computed properties herein depend on the form of the interaction potential.

A combination of theory, X-ray diffraction (XRD) and extended x-ray absorption fine structure (EXAFS) are used to probe the hydration structure of aqueous Na + . The high spatial resolution of the XRD measurements corresponds to Q max = 24 Å -1 while the first-reported Na K-edge EXAFS measurements have a spatial resolution corresponding to 2k = Q max = 16 Å -1 . Both provide an accurate measure of the shape and position of the first peak in the Na-O pair distribution function, g NaO (r). The measured Na-O distances of 2.384 ± 0.003 Å (XRD) and 2.37 ± 0.024 Å (EXAFS) are in excellent agreement. These measurements show a much shorter Na-O distance than generally reported in the experimental literature (Na-O avg ∼ 2.44 Å) although the current measurements are in agreement with recent neutron diffraction measurements. The measured Na-O coordination number from XRD is 5.5 ± 0.3. The measured structure is compared with both classical and first-principles density functional theory (DFT) simulations. Both of the DFT-based methods, revPBE and BLYP, predict a Na-O distance that is too long by about 0.05 Å with respect to the experimental data (EXAFS and XRD). The inclusion of dispersion interactions (-D3 and -D2) significantly worsens the agreement with experiment by further increasing the Na-O distance by 0.07 Å. In contrast, the use of a classical Na-O Lennard-Jones potential with SPC/E water accurately predicts the Na-O distance as 2.39 Å although the Na-O peak is over-structured with respect to experiment.

An ability to develop sequence-defined synthetic polymers that both mimic lipid amphiphilicity for self-assembly of highly stable membrane-mimetic 2D nanomaterials and exhibit protein-like functionality would revolutionize the development of biomimetic membranes. Here we report the assembly of lipid-like peptoids into highly stable, crystalline, free-standing and self-repairing membrane-mimetic 2D nanomaterials through a facile crystallization process. Both experimental and molecular dynamics simulation results show that peptoids assemble into membranes through an anisotropic formation process. We further demonstrated the use of peptoid membranes as a robust platform to incorporate and pattern functional objects through large side-chain diversity and/or co-crystallization approaches. Similar to lipid membranes, peptoid membranes exhibit changes in thickness upon exposure to external stimuli; they can coat surfaces in single layers and self-repair. We anticipate that this new class of membrane-mimetic 2D nanomaterials will provide a robust matrix for development of biomimetic membranes tailored to specific applications.