Editorial Commentary: A Revisit of an Old Clinical Dilemma-To Operate or Not to Operate on Acute Knee Anterior Cruciate Ligament Injuries.

There is a feeling among knee surgeons that operating on an acute anterior cruciate ligament injury will increase the incidence of arthrofibrosis. A recent systematic review and meta-analysis of 7 recent articles compared early versus delayed anterior cruciate ligament reconstruction. The conclusions were that the clinical and stability results were comparable in both groups.

Covalently deposited dyes: a new chromogen paradigm that facilitates analysis of multiple biomarkers in situ.

Multiplexed analysis of multiple biomarkers in a tissue sample requires use of reporter dyes with specific spectral properties that enable discrimination of signals. Conventional chromogens with broad absorbance spectra, widely used in immunohistochemistry (IHC), offer limited utility for multiplexed detection. Many dyes with narrow absorbance spectra, eg rhodamines, fluoresceins, and cyanines, potentially useful for multiplexed detection are well-characterized; however, generation of a chromogenic reagent useful for IHC analysis has not been demonstrated. Studies reported herein demonstrate utility of tyramine-chemistry for synthesis of a wide variety of new chromogenic dye conjugates useful for multiplexed in situ analysis using conventional light microscopes. The dyes, useful individually or in blends to generate new colors, provide signal sensitivity and dynamic range similar to conventional DAB chromogen, while enabling analysis of co-localized biomarkers. It is anticipated that this new paradigm will enable generation of a wide variety of new chromogens, useful for both research and clinical biomarker analysis that will benefit clinicians and patients.

Evaluation of Neuroleptic Utilization in the Intensive Care Unit During Transitions of Care.

PURPOSE: The purpose of this study was to identify risk factors associated with inappropriate continuation of neuroleptics postdischarge from the intensive care unit (ICU) and hospital. MATERIALS AND METHODS: A retrospective chart review was performed including all patients greater than 18 years of age who received neuroleptic medications in an ICU. RESULTS: One hundred sixty-one patients were included during the 12- month study period. There were 85 (53%) patients discharged from the ICU with inappropriate continuation of a neuroleptic medication. There were 54 (34%) patients discharged from the hospital with inappropriate continuation of a neuroleptic medication. Patients were more likely to be discharged from the ICU with an inappropriate neuroleptic if they were prescribed multiple neuroleptics ( P = .02), did not have a urine drug screen collected at admission ( P = .023), or if trazodone was utilized in their therapy ( P = .004). Patients were more likely to be discharged from the hospital with a neuroleptic if they had multiple neuroleptic orders ( P = .0001) or if trazodone was utilized in their therapy ( P = .0023). CONCLUSION: Risk factors associated with the continuation of inappropriate neuroleptic medications upon discharge from the ICU or the hospital include multiple neuroleptic medications prescribed, the lack of a urine drug screen upon admission, and the utilization of trazodone.

Early-onset pediatric atopic dermatitis is TH2 but also TH17 polarized in skin.

BACKGROUND: Atopic dermatitis (AD) affects 15% to 25% of children and 4% to 7% of adults. Paradigm-shifting discoveries about AD have been based on adult biomarkers, reflecting decades of disease activity, although 85% of cases begin by 5 years. Blood phenotyping shows only TH2 skewing in patients with early-onset pediatric AD, but alterations in early pediatric skin lesions are unknown, limiting advancement of targeted therapies. OBJECTIVE: We sought to characterize the early pediatric AD skin phenotype and its differences from pediatric control subjects and adults with AD. METHODS: Using immunohistochemistry and quantitative real-time PCR, we assessed biopsy specimens from 19 children with AD younger than 5 years within 6 months of disease onset in comparison with adults with AD or psoriasis and pediatric and adult control subjects. RESULTS: In lesional skin children showed comparable or greater epidermal hyperplasia (thickness and keratin 16) and cellular infiltration (CD3+, CD11c+, and FcεRI+) than adults with AD. Similar to adults, strong activation of the TH2 (IL-13, IL-31, and CCL17) and TH22 (IL-22 and S100As) axes and some TH1 skewing (IFN-γ and CXCL10) were present. Children showed significantly higher induction of TH17-related cytokines and antimicrobials (IL-17A, IL-19, CCL20, LL37, and peptidase inhibitor 3/elafin), TH9/IL-9, IL-33, and innate markers (IL-8) than adults (P < .02). Despite the characteristic downregulation in adult patients with AD, filaggrin expression was similar in children with AD and healthy children. Nonlesional skin in pediatric patients with AD showed higher levels of inflammation (particularly IL-17A and the related molecules IL-19 and LL37) and epidermal proliferation (keratin 16 and S100As) markers (P < .001). CONCLUSION: The skin phenotype of new-onset pediatric AD is substantially different from that of adult AD. Although excess TH2 activation characterizes both, TH9 and TH17 are highly activated at disease initiation. Increases in IL-19 levels might link TH2 and TH17 activation.

Advanced Age Does Not Worsen Recovery or Long-Term Morbidity After Postmastectomy Breast Reconstruction.

PURPOSE: Despite evidence that older women have quality-of-life outcomes similar to younger women after postmastectomy breast reconstruction (PMBR), they rarely receive it. There is a perception that PMBR in older women may result in significant physical morbidity. However, the effects of age on physical morbidity after PMBR have not been studied. This study sought to assess perceptions of recovery from surgery and long-term chest and upper body morbidity in older women who receive PMBR. METHODS: Women with American Joint Committee on Cancer stage 0-III breast cancer who underwent a mastectomy with PMBR between 2005 and 2011 were surveyed to assess their functional health status (DUKE), physical well-being (BREAST-Q), and perceptions of recovery from surgery. Patients were stratified into 2 age groups: older (≥65 years) and younger (<65 years). Outcome scores were compared by mastectomy laterality, reconstruction type, and between age groups. Data were analyzed using χ² and t tests. RESULTS: One hundred eight older and 103 younger patients returned surveys (response rate, 75.4%). The median time from mastectomy to survey was 4 years (range, 1-7). Younger women were more likely to undergo bilateral mastectomy than older women (65.7% vs 32.2%, P < 0.001). Some women (66.9%) underwent implant-only reconstruction and 33.1% underwent autologous reconstruction; there were no significant differences in reconstruction type between age groups. Patients who underwent unilateral and bilateral mastectomy had similar mean BREAST-Q physical well-being scores (79.4 vs 78.9, respectively, P = 0.85). There was no difference in mean physical well-being scores between older and younger patients (80.0 vs 78.5, respectively, P = 0.61). In addition, older patients were less likely to perceive their recovery from PMBR as being difficult than younger patients, though this was not statistically significant (48.2% vs 64.3%, P = 0.07). CONCLUSIONS: Older women who undergo PMBR have physical and upper body well-being that is similar to younger women. In addition, their perception of recovery from PMBR is at least as good as that seen in younger women. Older women contemplating PMBR should be counseled that they are not at higher risk for long-term physical and upper body morbidity from PMBR than are younger women.

The quality-of-life benefits of breast reconstruction do not diminish with age.

BACKGROUND AND OBJECTIVES: Older women rarely receive post-mastectomy breast reconstruction (PMBR). While there is a perception that PMBR is less beneficial in this age group, quality-of-life (QOL) data related to PMBR in older women remain scarce. METHODS: Women with AJCC stage 0-III breast cancer who underwent a mastectomy were surveyed. Respondents included 215 older women (≥ 65 years), of whom 36.0% received PMBR, and a control group of 101 younger women (< 65 years), all of whom received PMBR. Patient-reported outcomes were measured using the Duke Health Profile and the BREAST-Q. RESULTS: The survey response rate was 74.9%. An age-matched comparison of older women with and without PMBR revealed no significant differences in physical health, anxiety, or depression scores; however, PMBR was associated with greater breast satisfaction (P = 0.002) and greater breast-related psychosocial well-being (P = 0.02) than mastectomy alone. Among those who received PMBR, there was no correlation between age and breast satisfaction, psychosocial well-being, nor satisfaction with the outcome (P = 0.11, 0.21, and 0.56). CONCLUSIONS: Older women who undergo PMBR have better breast-related QOL outcomes than those who do not. Moreover, the outcomes of PMBR in older women are similar to those seen in younger women. When appropriate, older women should be encouraged to consider PMBR.

X-ray microscopy as an approach to increasing accuracy and efficiency of serial block-face imaging for correlated light and electron microscopy of biological specimens.

The recently developed three-dimensional electron microscopic (EM) method of serial block-face scanning electron microscopy (SBEM) has rapidly established itself as a powerful imaging approach. Volume EM imaging with this scanning electron microscopy (SEM) method requires intense staining of biological specimens with heavy metals to allow sufficient back-scatter electron signal and also to render specimens sufficiently conductive to control charging artifacts. These more extreme heavy metal staining protocols render specimens light opaque and make it much more difficult to track and identify regions of interest (ROIs) for the SBEM imaging process than for a typical thin section transmission electron microscopy correlative light and electron microscopy study. We present a strategy employing X-ray microscopy (XRM) both for tracking ROIs and for increasing the efficiency of the workflow used for typical projects undertaken with SBEM. XRM was found to reveal an impressive level of detail in tissue heavily stained for SBEM imaging, allowing for the identification of tissue landmarks that can be subsequently used to guide data collection in the SEM. Furthermore, specific labeling of individual cells using diaminobenzidine is detectable in XRM volumes. We demonstrate that tungsten carbide particles or upconverting nanophosphor particles can be used as fiducial markers to further increase the precision and efficiency of SBEM imaging.

The incidence of thrombocytopenia associated with continuous renal replacement therapy in critically ill patients.

INTRODUCTION: Thrombocytopenia in the intensive care unit (ICU) is a commonly experienced complication; the pathology is not always easily understood. Continuous renal replacement therapy (CRRT) provides a method to dialyze unstable critically ill patients. We hypothesized that CRRT may precipitate a form of thrombocytopenia. In trials thrombocytopenia occurred at rates as high as 70%. The etiology remains unknown and results in additional diagnostic workup, as well as possible drug therapy. The extent, duration and temporal relation of thrombocytopenia remain to be determined. OBJECTIVES: Identify a pattern in platelet fluctuations after the initiation of CRRT and its impact on health care. METHODS: A retrospective study was conducted in patients receiving CRRT for >24 h with no pre-existing thrombocytopenia. Patients initiated on CRRT had daily platelet counts monitored, and CRRT attributes and therapeutic interventions were collected. Platelets were assessed for time to nadir, degree of decline and time to return to baseline after discontinuation of CRRT. RESULTS: Forty-nine patients met inclusion criteria. Thirty-seven percent of patients receiving heparinoids were tested for heparin-induced thrombocytopenia (HIT), during CRRT, with 39% of these patients having therapy changed to non-heparinoid agents due to suspected HIT; no HIT antibodies were positive. Eleven patients (22%) receiving anticoagulants, prophylactically or therapeutically had them held for a drop in platelets. There was a mean decline in platelets of 48% with a mean of 4.6 days to the nadir. An average 2.48 days were observed until rebound to >150 × 10(3)/mm(3). Statistical analysis failed to identify any patient attributes that correlated with the probability of thrombocytopenia. CONCLUSION: CRRT appears to be associated with a drop in platelets within the first 5 days of therapy with an average decline of 48%. However, platelets appear to return to >150 × 10(3)/mm(3) after cessation of CRRT. This fluctuation should be considered in the setting of patients developing thrombocytopenia after initiation of CRRT.

Potential exposure of pollinators to neonicotinoid insecticides from the use of insecticide seed treatments in the mid-southern United States.

Research was done during 2012 to evaluate the potential exposure of pollinators to neonicotinoid insecticides used as seed treatments on corn, cotton, and soybean. Samples were collected from small plot evaluations of seed treatments and from commercial fields in agricultural production areas in Arkansas, Mississippi, and Tennessee. In total, 560 samples were analyzed for concentrations of clothianidin, imidacloprid, thiamethoxam, and their metabolites. These included pollen from corn and cotton, nectar from cotton, flowers from soybean, honey bees, Apis mellifera L., and pollen carried by foragers returning to hives, preplanting and in-season soil samples, and wild flowers adjacent to recently planted fields. Neonicotinoid insecticides were detected at a level of 1 ng/g or above in 23% of wild flower samples around recently planted fields, with an average detection level of about 10 ng/g. We detected neonicotinoid insecticides in the soil of production fields prior to planting at an average concentration of about 10 ng/g, and over 80% of the samples having some insecticide present. Only 5% of foraging honey bees tested positive for the presence of neonicotinoid insecticides, and there was only one trace detection (< 1 ng/g) in pollen being carried by those bees. Soybean flowers, cotton pollen, and cotton nectar contained little or no neonicotinoids resulting from insecticide seed treatments. Average levels of neonicotinoid insecticides in corn pollen ranged from less than 1 to 6 ng/g. The highest neonicotinoid concentrations were found in soil collected during early flowering from insecticide seed treatment trials. However, these levels were generally not well correlated with neonicotinoid concentrations in flowers, pollen, or nectar. Concentrations in flowering structures were well below defined levels of concern thought to cause acute mortality in honey bees. The potential implications of our findings are discussed.

Spatial Organization of Lipid Nanoparticle siRNA Delivery Systems Revealed by an Integrated Magnetic Resonance Approach.

Lipid nanoparticles (LNPs) are increasingly finding applications in targeted drug delivery, including for subcutaneous, intravenous, inhalation, and vaccine administration. While a variety of microscopy techniques are widely used for LNP characterization, their resolution does not allow for characterization of the spatial organization of different components, such as the excipients, targeting agents, or even the active ingredient. Herein, an approach is presented to probe the spatial organization of individual constituent groups of LNPs used for siRNA-based drug delivery, currently in clinical trials, by multinuclear solid-state magic-angle-spinning nuclear magnetic resonance (MAS NMR) spectroscopy. Dynamic nuclear polarization is exploited (DNP) for sensitivity enhancement, together with judicious 2H labeing, to detect functionally important LNP constituents, the siRNA and the targeting agent (<1-2 w/v%), respectively, and achieve a structural model of the LNP locating the siRNA in the core, the targeting agent below the surface, and the sugars above the lipid bilayer at the surface. The integrated approach presented here is applicable for structural analysis of LNPs and can be extended more generally to other multi-component biological formulations.

Thioredoxin, the processivity factor, sequesters an exposed cysteine in the thumb domain of bacteriophage T7 DNA polymerase.

Gene 5 protein (gp5) of bacteriophage T7 is a non-processive DNA polymerase. It achieves processivity by binding to Escherichia coli thioredoxin (trx). gp5/trx complex binds tightly to a primer-DNA template enabling the polymerization of hundreds of nucleotides per binding event. gp5 contains 10 cysteines. Under non-reducing condition, exposed cysteines form intermolecular disulfide linkages resulting in the loss of polymerase activity. No disulfide linkage is detected when Cys-275 and Cys-313 are replaced with serines. Cys-275 and Cys-313 are located on loop A and loop B of the thioredoxin binding domain, respectively. Replacement of either cysteine with serine (gp5-C275S, gp5-C313S) drastically decreases polymerase activity of gp5 on dA(350)/dT(25). On this primer-template gp5/trx in which Cys-313 or Cys-275 is replaced with serine have 50 and 90%, respectively, of the polymerase activity observed with wild-type gp5/trx. With single-stranded M13 DNA as a template gp5-C275S/trx retains 60% of the polymerase activity of wild-type gp5/trx. In contrast, gp5-C313S/trx has only one-tenth of the polymerase activity of wild-type gp5/trx on M13 DNA. Both wild-type gp5/trx and gp5-C275S/trx catalyze the synthesis of the entire complementary strand of M13 DNA, whereas gp5-C313S/trx has difficulty in synthesizing DNA through sites of secondary structure. gp5-C313S fails to form a functional complex with trx as measured by the apparent binding affinity as well as by the lack of a physical interaction with thioredoxin during hydroxyapatite-phosphate chromatography. Small angle x-ray scattering reveals an elongated conformation of gp5-C313S in comparison to a compact and spherical conformation of wild-type gp5.

Analysis of the structural integrity of SU-8-based optofluidic systems for small-molecule crystallization studies.

The use of SU-8-based optofluidic systems (OFS) is validated as an affordable and easy alternative to expensive glass device manufacturing for small-molecule crystallization studies and, in comparison with other polymers, able to withstand most organic solvents. A comparison between two identical OFS (using SU-8 and poly(dimethylsiloxane), PDMS) against the 36 most commonly used organic solvents for small-molecule crystallization studies have confirmed both the structural and optical stability of the SU-8, whereas PDMS suffered from unsealing or tearing in most cases. In order to test its compatibility, measurements before and after 24 h of continued exposure against solvents have been pursued. Here, three aspects have been considered: in the macroscale, swelling has been determined by analyzing the variations in the optical path in the OFS. For determining compatibility at microscale, fabricated SU-8 micropatterns were solvent-etched and subsequently characterized by scanning electron microscopy (SEM). Roughness of the polymer has also been studied through atomic force microscopy (AFM) measurements at the nanoscale. Experimental measurements of PDMS swelling were in accordance with previously reported observations, while SU-8 displayed a great stability against all the tested solvents. Through this experimental procedure we also show that the OFS are suitable for real-time, on-chip, UV-vis spectroscopy. Micro- and nanoscale observations did not show apparent corrosion on SU-8 surface. Also, two commonly used carrier fluids for microdroplet generation (FC-70 Fluorinert oil and silicone oil) were also tested against the different solvents with the aim of providing useful information for later microbatch experiments.

Stewardship approach for optimizing antimicrobial therapy through use of a rapid microarray assay on blood cultures positive for Enterococcus species.

Enterococci are a major cause of bloodstream infections in hospitalized patients and have limited antimicrobial treatment options due to their many resistance mechanisms. Molecular technologies have significantly shortened the time to enterococcal isolate identification compared with conventional methods. We evaluated the impact of rapid organism identification and resistance detection with the Verigene Gram-positive blood culture microarray assay on clinical and economic outcomes for patients with enterococcal bacteremia. A single-center preintervention/postintervention quasiexperimental study compared inpatients with enterococcal bacteremia from 1 February 2012 to 9 September 2012 (preintervention period) and 10 September 2012 to 28 February 2013 (postintervention period). An infectious disease and/or critical care pharmacist was contacted with the microarray assay results, and effective antibiotics were recommended. The clinical and economic outcomes for 74 patients were assessed. The mean time to appropriate antimicrobial therapy was 23.4 h longer in the preintervention group than in the postintervention group (P = 0.0054). A nonsignificant decrease in the mean time to appropriate antimicrobial therapy was seen for patients infected with vancomycin-susceptible Enterococcus isolates (P = 0.1145). For patients with vancomycin-resistant Enterococcus bacteremia, the mean time to appropriate antimicrobial therapy was 31.1 h longer in the preintervention group than in the postintervention group (P < 0.0001). In the postintervention group, the hospital length of stay was significantly 21.7 days shorter (P = 0.0484) and mean hospital costs were $60,729 lower (P = 0.02) than in the preintervention group. The rates of attributed deaths in the two groups were not statistically different. Microarray technology, supported by pharmacy and microbiology departments, can decrease the time to appropriate antimicrobial therapy, the hospital length of stay, and health care costs.

Thermodynamics of tetravalent thorium and uranium complexes from first-principles calculations.

Enthalpies of formation for the ThX4 and UX4 (X = F, Cl, OH) species have been investigated with density functional theory and coupled-cluster methods. ThX4 molecules are all confirmed as tetrahedral, while all UX4 molecules are predicted to adopt D2d symmetry using density functional theory. Multireference coupled cluster approaches confirm the D2d symmetry for UF4. The bonding is mostly ionic, and predicted formation energies for the halogen species show good agreement with experiment. Our calculated hydration energy of UF4 (-54.0 kcal/mol) is in very good agreement with the experimental data (-54.8 kcal/mol). We predict CCSD(T) formation energies of ΔfG[U(OH)4(g)] = -286.3 kcal/mol and ΔfG[U(OH)4(aq)] = -318.7 kcal/mol. ΔfG[U(OH)4(aq)] is 21 kcal/mol less stable than the established experimental thermodynamic data.

Optimization of Care for the Elderly Surgical Emergency Patient.

Geriatric patients undergoing emergency surgery are at significantly higher risk for complications and death when compared with younger patients. Optimizing care for these patients requires a multidisciplinary team, special attention to physiologic changes and medication use, as well as targeted intervention to mitigate complications such as delirium, which can worsen overall outcomes. Frailty can be assessed preoperatively to identify patients at the highest risk for complications. Shared decision-making with both the family and patient during the consent process is integral to defining patient's goals of care in these high-risk situations.

Seasonal variation in morphotype composition of pelagic Sargassum influx events is linked to oceanic origin.

The recent proliferation of pelagic Sargassum spp. in the Tropical Atlantic causes major ecological and socioeconomic impacts to the wider Caribbean when it washes ashore, with regional fisheries and tourism industries particularly affected. The Caribbean influxes have been tracked to a new bloom region known as the North Equatorial Recirculation Region (NERR) encompassing the area between the South Equatorial Current and the North Equatorial Counter Current and extending from Africa to South America. The vast biomass of Sargassum presents serious problems when it washes ashore but also represents significant commercial opportunities, especially with biofuel and fertilizer. The floating Sargassum mats are themselves diverse ecosystems that vary both in their biodiversity and biochemical attributes. Two major species (Sargassum fluitans and S. natans) have been identified as well as several distinguishable morphotypes of each. Oceanic mixing tends to blend the morphotypes together making it difficult to determine if there are regions of the NERR that favour bloom and growth of the distinct types. In this study, we quantify the species and morphotype composition of Sargassum strandings in Barbados and test if this is related to separate oceanic origins and routes travelled using a backtracking algorithm based on ocean drifter data. We found significant seasonal variation in the relative abundance of three morphotypes and this could be traced to two distinct easterly sub-origins and/or transport pathways; one area around 15° N that travels directly E-W across the Atlantic, and another area generally south of 10° N that takes a more meandering route coming close the coast of South America. These findings contribute towards our understanding of why the Tropical Atlantic bloom is presently occurring as well as towards addressing valorisation constraints surrounding variation in the supply of the three commonly occurring morphotypes.

Impact of Fluid Balance on Intensive Care Unit Length of Stay in Critically Ill Trauma Patients.

BACKGROUND: There is significant data in the medical and surgical literature supporting the correlations between positive volume balance and negative outcomes such as AKI, prolonged mechanical ventilation, intensive care unit and hospital length of stay and increased mortality. METHODS: This single-center, retrospective chart review included adult patients identified from a Trauma Registry database. The primary outcome was the total ICU LOS. Secondary outcomes include hospital LOS, ventilator-free days, incidence of compartment syndrome, acute respiratory distress syndrome (ARDS), renal replacement therapy (RRT), and days of vasopressor therapy. RESULTS: In general, baseline characteristics were similar between groups with the exception of mechanism of injury, FAST exam, and disposition from the ED. The ICU LOS was shortest in the negative fluid balance and longest in the positive fluid balance group (4 days vs 6 days, P = .001). Hospital LOS was also shorter in the negative balance group than that of the positive balance group (7 days vs 12 days, P < .001). More patients in the positive balance group experienced acute respiratory distress syndrome compared to the negative balance group (6.3% vs 0%, P = .004). There was no significant difference in the incidence of renal replacement therapy, days of vasopressor therapy, or ventilator-free days. DISCUSSION: A negative fluid balance at seventy-two hours was associated with a shorter ICU and hospital LOS in critically ill trauma patients. Our observed correlation between positive volume balance and total ICU days merits further exploration with prospective, comparative studies of lower volume resuscitation to key physiologic endpoints compared with routine standard of care.

Dichotomy in the definition of prescriptive information suggests both prescribed data and prescribed algorithms: biosemiotics applications in genomic systems.

The fields of molecular biology and computer science have cooperated over recent years to create a synergy between the cybernetic and biosemiotic relationship found in cellular genomics to that of information and language found in computational systems. Biological information frequently manifests its "meaning" through instruction or actual production of formal bio-function. Such information is called prescriptive information (PI). PI programs organize and execute a prescribed set of choices. Closer examination of this term in cellular systems has led to a dichotomy in its definition suggesting both prescribed data and prescribed algorithms are constituents of PI. This paper looks at this dichotomy as expressed in both the genetic code and in the central dogma of protein synthesis. An example of a genetic algorithm is modeled after the ribosome, and an examination of the protein synthesis process is used to differentiate PI data from PI algorithms.

Structure and hydrolysis of the U(IV), U(V), and U(VI) aqua ions from ab initio molecular simulations.

Ab initio molecular dynamics simulations at 300 K, based on density functional theory, are performed to study the hydration shell geometries, solvent dipole, and first hydrolysis reaction of the uranium(IV) (U(4+)) and uranyl(V) (UO(2)(+)) ions in aqueous solution. The solvent dipole and first hydrolysis reaction of aqueous uranyl(VI) (UO(2)(2+)) are also probed. The first shell of U(4+) is coordinated by 8-9 water ligands, with an average U-O distance of 2.42 Å. The average first shell coordination number and distance are in agreement with experimental estimates of 8-11 and 2.40-2.44 Å, respectively. The simulated EXAFS of U(4+) matches well with recent experimental data. The first shell of UO(2)(+) is coordinated by five water ligands in the equatorial plane, with the average U═O(ax) and U-O distances being 1.85 Å and 2.54 Å, respectively. Overall, the hydration shell structure of UO(2)(+) closely matches that of UO(2)(2+), except for small expansions in the average U═O(ax) and U-O distances. Each ion strongly polarizes their respective first-shell water ligands. The computed acidity constants (pK(a)) of U(4+) and UO(2)(2+) are 0.93 and 4.95, in good agreement with the experimental values of 0.54 and 5.24, respectively. The predicted pK(a) value of UO(2)(+) is 8.5.