Anisotropy in the dielectric spectrum of hydration water and its relation to water dynamics

Proteins, molecules, and macromolecular assemblies in water are surrounded by a nanometer-sized hydration layer with properties very different from bulk water. Here, we use classical molecular dynamics simulations to study the dielectric response of hydration water next to hydrophobic and hydrophilic planar surfaces. We find the interfacial dielectricabsorption of water to be strongly anisotropic: compared to bulk water, which shows a broad dielectricabsorption maximum around 15 GHz in the imaginary part of the dielectric function, the absorption for electric fields parallel to the surface is of similar strength and shows a slight redshift, while for perpendicular electric fields it is strongly attenuated and blueshifted. This anisotropy is generic for hydrophobic and hydrophilic surfaces. From our spatially resolved dielectric functions and a modified Maxwell-Garnett theory that accounts for anisotropic hydration layers around spherical particles, the dielectricabsorption of solutions of organic molecules and micelles is derived to exhibit the experimentally known attenuation in combination with a redshift. These two features are traced back to the subtle interplay of interfacial depolarization effects and the dielectricanisotropy in the hydration layer. By a detailed analysis of the individual water molecule dynamics the perpendicular blueshift is shown not to be linked to accelerated water reorientation, but rather to dielectric boundary effects. Carefully conducted angularly resolved experiments at planar aqueous interfaces will be able to resolve this dielectricanisotropy and thus to confirm the subtle connection between spectralabsorption features and the molecular water dynamics in hydration layers

Synthesis of β³-amino acid and peptides from D-ribose

<p>Synthesis of new β³-amino acid, peptides and conformational analysis are reported from d-ribose, using Wittig olefination and Aza-Michael addition.</p

Risk of Bacterial Coinfections in Febrile Infants 60 Days Old and Younger with Documented Viral Infections.

ObjectiveTo determine the risk of serious bacterial infections (SBIs) in young febrile infants with and without viral infections.Study designPlanned secondary analyses of a prospective observational study of febrile infants 60 days of age or younger evaluated at 1 of 26 emergency departments who did not have clinical sepsis or an identifiable site of bacterial infection. We compared patient demographics, clinical, and laboratory findings, and prevalence of SBIs between virus-positive and virus-negative infants.ResultsOf the 4778 enrolled infants, 2945 (61.6%) had viral testing performed, of whom 1200 (48.1%) were virus positive; 44 of the 1200 had SBIs (3.7%; 95% CI, 2.7%-4.9%). Of the 1745 virus-negative infants, 222 had SBIs (12.7%; 95% CI, 11.2%-14.4%). Rates of specific SBIs in the virus-positive group vs the virus-negative group were: UTIs (33 of 1200 [2.8%; 95% CI, 1.9%-3.8%] vs 186 of 1745 [10.7%; 95% CI, 9.2%-12.2%]) and bacteremia (9 of 1199 [0.8%; 95% CI, 0.3%-1.4%] vs 50 of 1743 [2.9%; 95% CI, 2.1%-3.8%]). The rate of bacterial meningitis tended to be lower in the virus-positive group (0.4%) than in the viral-negative group (0.8%); the difference was not statistically significant. Negative viral status (aOR, 3.2; 95% CI, 2.3-4.6), was significantly associated with SBI in multivariable analysis.ConclusionsFebrile infants ≤60 days of age with viral infections are at significantly lower, but non-negligible risk for SBIs, including bacteremia and bacterial meningitis

Risk of Bacterial Coinfections in Febrile Infants 60 Days Old and Younger with Documented Viral Infections.

ObjectiveTo determine the risk of serious bacterial infections (SBIs) in young febrile infants with and without viral infections.Study designPlanned secondary analyses of a prospective observational study of febrile infants 60 days of age or younger evaluated at 1 of 26 emergency departments who did not have clinical sepsis or an identifiable site of bacterial infection. We compared patient demographics, clinical, and laboratory findings, and prevalence of SBIs between virus-positive and virus-negative infants.ResultsOf the 4778 enrolled infants, 2945 (61.6%) had viral testing performed, of whom 1200 (48.1%) were virus positive; 44 of the 1200 had SBIs (3.7%; 95% CI, 2.7%-4.9%). Of the 1745 virus-negative infants, 222 had SBIs (12.7%; 95% CI, 11.2%-14.4%). Rates of specific SBIs in the virus-positive group vs the virus-negative group were: UTIs (33 of 1200 [2.8%; 95% CI, 1.9%-3.8%] vs 186 of 1745 [10.7%; 95% CI, 9.2%-12.2%]) and bacteremia (9 of 1199 [0.8%; 95% CI, 0.3%-1.4%] vs 50 of 1743 [2.9%; 95% CI, 2.1%-3.8%]). The rate of bacterial meningitis tended to be lower in the virus-positive group (0.4%) than in the viral-negative group (0.8%); the difference was not statistically significant. Negative viral status (aOR, 3.2; 95% CI, 2.3-4.6), was significantly associated with SBI in multivariable analysis.ConclusionsFebrile infants ≤60 days of age with viral infections are at significantly lower, but non-negligible risk for SBIs, including bacteremia and bacterial meningitis

Epidemiology of Bacteremia in Febrile Infants Aged 60 Days and Younger

Study objectiveTo describe the current epidemiology of bacteremia in febrile infants 60 days of age and younger in the Pediatric Emergency Care Applied Research Network (PECARN).MethodsWe conducted a planned secondary analysis of a prospective observational study of febrile infants 60 days of age and younger presenting to any of 26 PECARN emergency departments (2008 to 2013) who had blood cultures obtained. We excluded infants with significant comorbidities or critically ill appearance. The primary outcome was prevalence of bacteremia.ResultsOf 7,335 screened infants, 4,778 (65.1%) had blood cultures and were enrolled. Of these patients, 84 had bacteremia (1.8%; 95% confidence interval [CI] 1.4% to 2.2%). The prevalence of bacteremia in infants aged 28 days or younger (47/1,515) was 3.1% (95% CI 2.3% to 4.1%); in infants aged 29 to 60 days (37/3,246), 1.1% (95% CI 0.8% to 1.6%). Prevalence differed by week of age for infants 28 days of age and younger (0 to 7 days: 4/156, 2.6%; 8 to 14 days: 19/356, 5.3%; 15 to 21 days: 15/449, 3.3%; and 22 to 28 days: 9/554, 1.6%). The most common pathogens were Escherichia coli (39.3%; 95% CI 29.5% to 50.0%) and group B streptococcus (23.8%; 95% CI 16.0% to 33.9%). Bacterial meningitis occurred in 19 of 1,515 infants 28 days of age and younger (1.3%; 95% CI 0.8% to 2.0%) and 5 of 3,246 infants aged 29 to 60 days (0.2%; 95% CI 0.1% to 0.4%). Of 84 infants with bacteremia, 36 (42.9%; 95% CI 32.8% to 53.5%) had urinary tract infections (E coli 83%); 11 (13.1%; 95% CI 7.5% to 21.9%) had bacterial meningitis.ConclusionThe prevalence of bacteremia and meningitis among febrile infants 28 days of age and younger is high and exceeds that observed in infants aged 29 to 60 days. E coli and group B streptococcus are the most common bacterial pathogens

Epidemiology of Bacteremia in Febrile Infants Aged 60 Days and Younger

Study objectiveTo describe the current epidemiology of bacteremia in febrile infants 60 days of age and younger in the Pediatric Emergency Care Applied Research Network (PECARN).MethodsWe conducted a planned secondary analysis of a prospective observational study of febrile infants 60 days of age and younger presenting to any of 26 PECARN emergency departments (2008 to 2013) who had blood cultures obtained. We excluded infants with significant comorbidities or critically ill appearance. The primary outcome was prevalence of bacteremia.ResultsOf 7,335 screened infants, 4,778 (65.1%) had blood cultures and were enrolled. Of these patients, 84 had bacteremia (1.8%; 95% confidence interval [CI] 1.4% to 2.2%). The prevalence of bacteremia in infants aged 28 days or younger (47/1,515) was 3.1% (95% CI 2.3% to 4.1%); in infants aged 29 to 60 days (37/3,246), 1.1% (95% CI 0.8% to 1.6%). Prevalence differed by week of age for infants 28 days of age and younger (0 to 7 days: 4/156, 2.6%; 8 to 14 days: 19/356, 5.3%; 15 to 21 days: 15/449, 3.3%; and 22 to 28 days: 9/554, 1.6%). The most common pathogens were Escherichia coli (39.3%; 95% CI 29.5% to 50.0%) and group B streptococcus (23.8%; 95% CI 16.0% to 33.9%). Bacterial meningitis occurred in 19 of 1,515 infants 28 days of age and younger (1.3%; 95% CI 0.8% to 2.0%) and 5 of 3,246 infants aged 29 to 60 days (0.2%; 95% CI 0.1% to 0.4%). Of 84 infants with bacteremia, 36 (42.9%; 95% CI 32.8% to 53.5%) had urinary tract infections (E coli 83%); 11 (13.1%; 95% CI 7.5% to 21.9%) had bacterial meningitis.ConclusionThe prevalence of bacteremia and meningitis among febrile infants 28 days of age and younger is high and exceeds that observed in infants aged 29 to 60 days. E coli and group B streptococcus are the most common bacterial pathogens

Serious Bacterial Infections in Young Febrile Infants With Positive Urinalysis Results.

UNLABELLED: It is unknown whether febrile infants 29 to 60 days old with positive urinalysis results require routine lumbar punctures for evaluation of bacterial meningitis. OBJECTIVE: To determine the prevalence of bacteremia and/or bacterial meningitis in febrile infants ≤60 days of age with positive urinalysis (UA) results. METHODS: Secondary analysis of a prospective observational study of noncritical febrile infants ≤60 days between 2011 and 2019 conducted in the Pediatric Emergency Care Applied Research Network emergency departments. Participants had temperatures ≥38°C and were evaluated with blood cultures and had UAs available for analysis. We report the prevalence of bacteremia and bacterial meningitis in those with and without positive UA results. RESULTS: Among 7180 infants, 1090 (15.2%) had positive UA results. The risk of bacteremia was higher in those with positive versus negative UA results (63/1090 [5.8%] vs 69/6090 [1.1%], difference 4.7% [3.3% to 6.1%]). There was no difference in the prevalence of bacterial meningitis in infants ≤28 days of age with positive versus negative UA results (∼1% in both groups). However, among 697 infants aged 29 to 60 days with positive UA results, there were no cases of bacterial meningitis in comparison to 9 of 4153 with negative UA results (0.2%, difference -0.2% [-0.4% to -0.1%]). In addition, there were no cases of bacteremia and/or bacterial meningitis in the 148 infants ≤60 days of age with positive UA results who had the Pediatric Emergency Care Applied Research Network low-risk blood thresholds of absolute neutrophil count &lt;4 × 103 cells/mm3 and procalcitonin &lt;0.5 ng/mL. CONCLUSIONS: Among noncritical febrile infants ≤60 days of age with positive UA results, there were no cases of bacterial meningitis in those aged 29 to 60 days and no cases of bacteremia and/or bacterial meningitis in any low-risk infants based on low-risk blood thresholds in both months of life. These findings can guide lumbar puncture use and other clinical decision making