Kink-Controlled Gold Nanoparticles for Electrochemical Glucose Oxidation

Enzymes in nature efficiently catalyze chiral organic molecules by elaborately tuning the geometrical arrangement of atoms in the active site. However, enantioselective oxidation of organic molecules by heterogeneous electrocatalysts is challenging because of the difficulty in controlling the asymmetric structures of the active sites on the electrodes. Here, we show that the distribution of chiral kink atoms on high-index facets can be precisely manipulated even on single gold nanoparticles; and this enabled stereoselective oxidation of hydroxyl groups on various sugar molecules. We characterized the crystallographic orientation and the density of kink atoms and investigated their specific interactions with the glucose molecule due to the geometrical structure and surface electrostatic potential.

Interrupted SNAr-Alkylation Dearomatization

Dearomatizations provide powerful synthetic routes to rapidly assemble substituted carbocycles and heterocycles found in a plethora of bioactive molecules. Harnessing the advantages of dearomatization typically requires vigorous reagents because of the difficulty in disrupting the stable aromatic core. A relatively mild dearomatization strategy is described that employs lithiated nitriles or isocyanides in a simple SNAr-type addition to form σ-complexes that are trapped by alkylation. The dearomatizations are diastereoselective and efficient and rapidly install two new carbon-carbon bonds, one of which is a quaternary center, as well as nitrile, isocyanide, and cyclohexadiene functionalities.

Anomalous π-backbonding in complexes between B(SiR3)3 and N2: catalytic activation and breaking of scaling relations

Chemical transformations of molecular nitrogen (N2), including the nitrogen reduction reaction (NRR), are difficult to catalyze because of the weak Lewis basicity of N2. In this study, it is shown that Lewis acids of the types B(SiR3)3 and B(GeR3)3 bind N2 and CO with anomalously short and strong B-N or B-C bonds. B(SiH3)3·N2 has a B-N bond length of 1.48 Å and a complexation enthalpy of -15.9 kcal mol-1 at the M06-2X/jun-cc-pVTZ level. The selective binding enhancement of N2 and CO is due to π-backbonding from Lewis acid to Lewis base, as demonstrated by orbital analysis and density difference plots. The π-backbonding is found to be a consequence of constructive orbital interactions between the diffuse and highly polarizable B-Si and B-Ge bond regions and the π and π* orbitals of N2. This interaction is strengthened by electron donating substituents on Si or Ge. The π-backbonding interaction is predicted to activate N2 for chemical transformation and reduction, as it decreases the electron density and increases the length of the N-N bond. The binding of N2 and CO by the B(SiR3)3 and B(GeR3)3 types of Lewis acids also has a strong σ-bonding contribution. The relatively high σ-bond strength is connected to the highly positive surface electrostatic potential [VS(r)] above the B atom in the tetragonal binding conformation, but the σ-bonding also has a significant coordinate covalent (dative) contribution. Electron withdrawing substituents increase the potential and the σ-bond strength, but favor the binding of regular Lewis acids, such as NH3 and F-, more strongly than binding of N2 and CO. Molecules of the types B(SiR3)3 and B(GeR3)3 are chemically labile and difficult to synthesize. Heterogenous catalysts with the wanted B(Si-)3 or B(Ge-)3 bonding motif may be prepared by boron doping of nanostructured silicon or germanium compounds. B-doped and hydrogenated silicene is found to have promising properties as catalyst for the electrochemical NRR.

Trauma-registry survival outcome follow up: 30 days is mandatory and appears sufficient

INTRODUCTION

Thirty-day in-hospital mortality is a common outcome measure in trauma-registry research and benchmarking. However, this does not include deaths after hospital discharge before 30 days or late deaths beyond 30 days since the injury. To evaluate the reliability of this outcome measure, we assessed the timing and causes of death during the first year after major blunt trauma in patients treated at a single tertiary trauma center.

METHODS

We used the Helsinki Trauma Registry to identify severely injured (NISS ≥ 16) blunt trauma patients during 2006 to 2015. The Population Register center of Finland provided the mortality data for patients and Statistics Finland provided the cause of death information from death certificates. Disease, work-related disease, medical treatment, and unknown cause of death were considered as non-trauma related deaths. We divided the 1-year study period into the following three categories: in-hospital death before 30 days (Group 1), death after discharge but within 30 days (Group 2), and death 31 to 365 days since admission (Group 3).

RESULTS

We included 3557 patients with a median NISS of 29. Altogether, 21.8% (776/3557) patients died during the first year since the injury. Of these non-survivors, 12.7% (450) were in Group 1, 4.0% (141) in Group 2, and 5.2% (185) in Group 3. Non-traumatic deaths not directly related to the injury increased substantially as the time from the injury increased and were 2.0% (9/450) in Group 1, 13.5% (19/141) in Group 2, and 35.7% (66/185) in Group 3.

CONCLUSION

Thirty-day mortality is a proper outcome that measures survival after severe blunt trauma. However, applying only in-hospital mortality instead of actual 30-day mortality may exclude non-survivors who die at another facility before day 30. This could result in over-optimistic benchmarking results. On the other hand, extending the follow-up period beyond 30 days increases the rate of non-traumatic deaths. By combining data from different registries, it is possible to address this challenge in current trauma-registry research caused by lack of follow up.

Machine learning meets mechanistic modelling for accurate prediction of experimental activation energies

Accurate prediction of chemical reactions in solution is challenging for current state-of-the-art approaches based on transition state modelling with density functional theory. Models based on machine learning have emerged as a promising alternative to address these problems, but these models currently lack the precision to give crucial information on the magnitude of barrier heights, influence of solvents and catalysts and extent of regio- and chemoselectivity. Here, we construct hybrid models which combine the traditional transition state modelling and machine learning to accurately predict reaction barriers. We train a Gaussian Process Regression model to reproduce high-quality experimental kinetic data for the nucleophilic aromatic substitution reaction and use it to predict barriers with a mean absolute error of 0.77 kcal mol⁻¹ for an external test set. The model was further validated on regio- and chemoselectivity prediction on patent reaction data and achieved a competitive top-1 accuracy of 86%, despite not being trained explicitly for this task. Importantly, the model gives error bars for its predictions that can be used for risk assessment by the end user. Hybrid models emerge as the preferred alternative for accurate reaction prediction in the very common low-data situation where only 100–150 rate constants are available for a reaction class. With recent advances in deep learning for quickly predicting barriers and transition state geometries from density functional theory, we envision that hybrid models will soon become a standard alternative to complement current machine learning approaches based on ground-state physical organic descriptors or structural information such as molecular graphs or fingerprints.

Hybrid reactivity models, combining mechanistic calculations and machine learning with descriptors, are used to predict barriers for nucleophilic aromatic substitution.

How to Validate Data Quality in a Trauma Registry? The Helsinki Trauma Registry Internal Audit

BACKGROUND AND AIMS

Trauma registry data are used for analyzing and improving patient care, comparison of different units, and for research and administrative purposes. Data should therefore be reliable. The aim of this study was to audit the quality of the Helsinki Trauma Registry internally. We describe how to conduct a validation of a regional or national trauma registry and how to report the results in a readily comprehensible form.

MATERIALS AND METHODS

Trauma registry database of Helsinki Trauma Registry from year 2013 was re-evaluated. We assessed data quality in three different parts of the data input process: the process of including patients in the trauma registry (case completeness); the process of calculating Abbreviated Injury Scale (AIS) codes; and entering the patient variables in the trauma registry (data completeness, accuracy, and correctness). We calculated the case completeness results using raw agreement percentage and Cohen's κ value. Percentage and descriptive methods were used for the remaining calculations.

RESULTS

In total, 862 patients were evaluated; 853 were rated the same in the audit process resulting in a raw agreement percentage of 99%. Nine cases were missing from the registry, yielding a case completeness of 97.1% for the Helsinki Trauma Registry. For AIS code data, we analyzed 107 patients with severe thorax injury with 941 AIS codes. Completeness of codes was 99.0% (932/941), accuracy was 90.0% (841/932), and correctness was 97.5% (909/932). The data completeness of patient variables was 93.4% (3899/4174). Data completeness was 100% for 16 of 32 categories. Data accuracy was 94.6% (3690/3899) and data correctness was 97.2% (3789/3899).

CONCLUSION

The case completeness, data completeness, data accuracy, and data correctness of the Helsinki Trauma Registry are excellent. We recommend that these should be the variables included in a trauma registry validation process, and that the quality of trauma registry data should be systematically and regularly reviewed and reported.

Asymmetric Synthesis of Adjacent Tri- and Tetrasubstituted Carbon Stereocenters: Organocatalytic Aldol Reaction of an Hydantoin Surrogate with Azaarene 2-Carbaldehydes

A bifunctional amine/squaramide catalyst promoted direct aldol addition of an hydantoin surrogate to pyridine 2-carbaldehyde N-oxides to afford adducts bearing two vicinal tertiary/quaternary carbons in high diastereo- and enantioselectivity (d.r. up to >20:1; ee up to 98 %) is reported. Acid hydrolysis of adducts followed by reduction of the N-oxide group yields enantiopure carbinol-tethered quaternary hydantoin-azaarene conjugates with densely functionalized skeletons. DFT studies of the potential energy surface (B3LYP/6-31+G(d)+CPCM (dichloromethane)) of the reaction correlate the activity of different catalysts and support an intramolecular hydrogen-bond-assisted activation of the squaramide moiety in the transition state of the catalytic reaction.

Blunt Abdominal Trauma in a European Trauma Setting: Need for Complex or Non-Complex Skills in Emergency Laparotomy

BACKGROUND AND AIMS

Blunt abdominal trauma can lead to substantial organ injury and hemorrhage necessitating open abdominal surgery. Currently, the trend in surgeon training is shifting away from general surgery and the surgical treatment of blunt abdominal trauma patients is often done by sub-specialized surgeons. The aim of this study was to identify what emergency procedures are needed after blunt abdominal trauma and whether they can be performed with the skill set of a general surgeon.

MATERIALS AND METHODS

The records of blunt abdominal trauma patients requiring emergency laparotomy (n = 100) over the period 2006-2016 (Helsinki University Hospital Trauma Registry) were reviewed. The organ injuries and the complexity of the procedures were evaluated.

RESULTS

A total of 89 patients (no need for complex skills, NCS) were treated with the skill set of general surgeons while 11 patients required complex skills. Complex skills patients were more severely injured (New Injury Severity Score 56.4 vs 35.9, p < 0.001) and had a lower systolic blood pressure (mean: 89 vs 112, p = 0.044) and higher mean shock index (heart rate/systolic blood pressure: 1.43 vs 0.95, p = 0.012) on admission compared with NCS patients. The top three NCS procedures were splenectomy (n = 33), bowel repair (n = 31), and urinary bladder repair (n = 16). In patients requiring a complex procedure (CS), the bleeding site was the liver (n = 7) or a major blood vessel (n = 4).

CONCLUSION

The majority of patients requiring emergency laparotomy can be managed with the skills of a general surgeon. Non-responder blunt abdominal trauma patients with positive ultrasound are highly likely to require complex skills. The future training of surgeons should concentrate on NCS procedures while at the same time recognizing those injuries requiring complex skills.

The local electron attachment energy and the electrostatic potential as descriptors of surface–adsorbate interactions

Local DFT-based properties are used for fast rationalization and accurate estimations of local surface reactivity of metal and oxide compounds.

Fragment molecular orbital study of the cAMP-dependent protein kinase catalyzed phosphoryl transfer: a comparison with the differential transition state stabilization method

The importance of key residues to the activity of the cAMP-dependent protein kinase catalyzed phosphoryl transfer and to the stabilization of the transition state of the reaction has been investigated by means of the fragment molecular orbital (FMO) method. To evaluate the accuracy of the method and its capability of fragmenting covalent bonds, we have compared stabilization energies due to the interactions between individual residues and the reaction center to results obtained with the differential transition state stabilization method (Szarek, et al., J. Phys. Chem. B, 2008, 112, 11819-11826) and observe, despite a size difference in the fragment describing the reaction center, near-quantitative agreement. We have also computed deletion energies to investigate the effect of virtual deletion of key residues on the activation energy. These results are consistent with the stabilization energies and yield additional information as they clearly capture the effect of secondary interactions, i.e. interactions in the second coordination layer of the reaction center. We find that using FMO to calculate deletion energies is a powerful and time efficient approach to analyze the importance of key residues to the activity of an enzyme catalyzed reaction.

σ-Holes and σ-lumps direct the Lewis basic and acidic interactions of noble metal nanoparticles: introducing regium bonds

Using local DFT-based probes for electrostatic as well as charge transfer/polarization interactions, we are able to characterize Lewis basic and acidic sites on copper, silver and gold nanoparticles.

Mechanism and regioselectivity of electrophilic aromatic nitration in solution: the validity of the transition state approach

The potential energy surfaces in gas phase and in aqueous solution for the nitration of benzene, chlorobenzene, and phenol have been elucidated with density functional theory at the M06-2X/6-311G(d,p) level combined with the polarizable continuum solvent model (PCM). Three reaction intermediates have been identified along both surfaces: the unoriented π-complex (I), the oriented reaction complex (II), and the σ-complex (III). In order to obtain quantitatively reliable results for positional selectivity and for modeling the expulsion of the proton, it is crucial to take solvent effects into consideration. The results are in agreement with Olah’s conclusion from over 40 years ago that the transition state leading to (II) is the rate-determining step in activated cases, while it is the one leading to (III) for deactivated cases. The simplified reactivity approach of using the free energy for the formation of (III) as a model of the rate-determining transition state has previously been shown to be very successful for halogenations, but problematic for nitrations. These observations are rationalized with the geometric and energetic resemblance, and lack of resemblance respectively, between (III) and the corresponding rate determining transition state. At this level of theory, neither the σ-complex (III) nor the reaction complex (II) can be used to accurately model the rate-determining transition state for nitrations.

MD Simulations Reveal Complex Water Paths in Squalene-Hopene Cyclase: Tunnel-Obstructing Mutations Increase the Flow of Water in the Active Site

Squalene-hopene cyclase catalyzes the cyclization of squalene to hopanoids. A previous study has identified a network of tunnels in the protein, where water molecules have been indicated to move. Blocking these tunnels by site-directed mutagenesis was found to change the activation entropy of the catalytic reaction from positive to negative with a concomitant lowering of the activation enthalpy. As a consequence, some variants are faster and others are slower than the wild type (wt) in vitro under optimal reaction conditions for the wt. In this study, molecular dynamics (MD) simulations have been performed for the wt and the variants to investigate how the mutations affect the protein structure and the water flow in the enzyme, hypothetically influencing the activation parameters. Interestingly, the tunnel-obstructing variants are associated with an increased flow of water in the active site, particularly close to the catalytic residue Asp376. MD simulations with the substrate present in the active site indicate that the distance for the rate-determining proton transfer between Asp376 and the substrate is longer in the tunnel-obstructing protein variants than in the wt. On the basis of the previous experimental results and the current MD results, we propose that the tunnel-obstructing variants, at least partly, could operate by a different catalytic mechanism, where the proton transfer may have contributions from a Grotthuss-like mechanism.

Dehydrogenation of methanol on Cu2O(100) and (111)

Adsorption and desorption of methanol on the (111) and (100) surfaces of Cu₂O have been studied using high-resolution photoelectron spectroscopy in the temperature range 120-620 K, in combination with density functional theory calculations and sum frequency generation spectroscopy. The bare (100) surface exhibits a (3,0; 1,1) reconstruction but restructures during the adsorption process into a Cu-dimer geometry stabilized by methoxy and hydrogen binding in Cu-bridge sites. During the restructuring process, oxygen atoms from the bulk that can host hydrogen appear on the surface. Heating transforms methoxy to formaldehyde, but further dehydrogenation is limited by the stability of the surface and the limited access to surface oxygen. The (√3 × √3)R30°-reconstructed (111) surface is based on ordered surface oxygen and copper ions and vacancies, which offers a palette of adsorption and reaction sites. Already at 140 K, a mixed layer of methoxy, formaldehyde, and CH_xO_y is formed. Heating to room temperature leaves OCH and CH_x. Thus both CH-bond breaking and CO-scission are active on this surface at low temperature. The higher ability to dehydrogenate methanol on (111) compared to (100) is explained by the multitude of adsorption sites and, in particular, the availability of surface oxygen.

Accuracy and Coverage of Diagnosis and Procedural Coding of Severely Injured Patients in the Finnish Hospital Discharge Register: Comparison to Patient Files and the Helsinki Trauma Registry

Background and Aims:

The Finnish Hospital Discharge Register data are frequently used for research purposes. The Finnish Hospital Discharge Register has shown excellent validity in single injuries or disease groups, but no studies have assessed patients with multiple trauma diagnoses. We aimed to evaluate the accuracy and coverage of the Finnish Hospital Discharge Register but at the same time validate the data of the trauma registry of the Helsinki University Hospital’s Trauma Unit.

Materials and Methods:

We assessed the accuracy and coverage of the Finnish Hospital Discharge Register data by comparing them to the original patient files and trauma registry files from the trauma registry of the Helsinki University Hospital’s Trauma Unit. We identified a baseline cohort of patients with severe thorax injury from the trauma registry of the Helsinki University Hospital’s Trauma Unit of 2013 (sample of 107 patients). We hypothesized that the Finnish Hospital Discharge Register would lack valuable information about these patients.

Results:

Using patient files, we identified 965 trauma diagnoses in these 107 patients. From the Finnish Hospital Discharge Register, we identified 632 (65.5%) diagnoses and from the trauma registry of the Helsinki University Hospital’s Trauma Unit, 924 (95.8%) diagnoses. A total of 170 (17.6%) trauma diagnoses were missing from the Finnish Hospital Discharge Register data and 41 (4.2%) from the trauma registry of the Helsinki University Hospital’s Trauma Unit data. The coverage and accuracy of diagnoses in the Finnish Hospital Discharge Register were 65.5% (95% confidence interval: 62.5%–68.5%) and 73.8% (95% confidence interval: 70.4%–77.2%), respectively, and for the trauma registry of the Helsinki University Hospital’s Trauma Unit, 95.8% (95% confidence interval: 94.5%–97.0%) and 97.6% (95% confidence interval: 96.7%–98.6%), respectively. According to patient records, these patients were subjects in 249 operations. We identified 40 (16.1%) missing operation codes from the Finnish Hospital Discharge Register and 19 (7.6%) from the trauma registry of the Helsinki University Hospital’s Trauma Unit.

Conclusion:

The validity of the Finnish Hospital Discharge Register data is unsatisfactory in terms of the accuracy and coverage of diagnoses in patients with multiple trauma diagnoses. Procedural codes provide greater accuracy. We found the coverage and accuracy of the trauma registry of the Helsinki University Hospital’s Trauma Unit to be excellent. Therefore, a special trauma registry, such as the trauma registry of the Helsinki University Hospital’s Trauma Unit, provides much more accurate data and should be the preferred registry when extracting data for research or for administrative use, such as resource prioritizing.

Dual Lewis Acid/Lewis Base Catalyzed Acylcyanation of Aldehydes: A Mechanistic Study

A mechanistic investigation, which included a Hammett correlation analysis, evaluation of the effect of variation of catalyst composition, and low-temperature NMR spectroscopy studies, of the Lewis acid-Lewis base catalyzed addition of acetyl cyanide to prochiral aldehydes provides support for a reaction route that involves Lewis base activation of the acyl cyanide with formation of a potent acylating agent and cyanide ion. The cyanide ion adds to the carbonyl group of the Lewis acid activated aldehyde. O-Acylation by the acylated Lewis base to form the final cyanohydrin ester occurs prior to decomplexation from titanium. For less reactive aldehydes, the addition of cyanide is the rate-determining step, whereas, for more reactive, electron-deficient aldehydes, cyanide addition is rapid and reversible and is followed by rate-limiting acylation. The resting state of the catalyst lies outside the catalytic cycle and is believed to be a monomeric titanium complex with two alcoholate ligands, which only slowly converts into the product.

External validation of the Norwegian survival prediction model in trauma after major trauma in Southern Finland

BACKGROUND

The Norwegian Survival Prediction Model in Trauma (NORMIT) is a newly developed outcome prediction model for patients with trauma. We aimed to compare the novel NORMIT to the more commonly used Trauma and Injury Severity Score (TRISS) in Finnish trauma patients.

METHODS

We performed a retrospective open-cohort study, using the trauma registry of Helsinki university hospital's trauma unit, including severely injured patients (new injury severity score > 15) admitted from 2007 to 2011. We used 30-day in-hospital mortality as the primary outcome, and discharge functional outcome as a secondary outcome of interest. Model performance was evaluated by comparing discrimination (by area under the receiver operating characteristic curve [AUC]), using a re-sample bootstrap technique, and by assessing calibration (GiViTI belt).

RESULTS

We identified 1111 patients fulfilling the study inclusion criteria. Overall mortality was 13% (n = 147). NORMIT showed slightly better discrimination for mortality prediction (AUC = 0.83, 95% confidence interval [CI] = 0.80-0.86 vs. AUC = 0.79, 95% CI = 0.75-0.83, P = 0.004) and functional outcome prediction (AUC = 0.78, 95% CI = 0.76-0.82 vs. AUC = 0.75, 95% CI = 0.72-0.78, P < 0.001) than TRISS. Calibration testing revealed poor calibration for both NORMIT and TRISS (P < 0.001), by giving too pessimistic predictions (predicted survival significantly lower than actual survival).

CONCLUSION

NORMIT and TRISS showed good discrimination, but poor calibration, in this mixed cohort of severely injured trauma patients from Southern Finland. We found NORMIT to be a feasible alternative to TRISS for trauma patient outcome prediction, but trauma prediction models with improved calibration are needed.

Reactivity at the Cu2O(100):Cu–H2O interface: a combined DFT and PES study

Detailed characterization of the structure and composition of the water–cuprite interface.

The Effect of Evolving Fluid Resuscitation on the Outcome of Severely Injured Patients: An 8-year Experience at a Tertiary Trauma Center

BACKGROUND AND AIMS

Fluid resuscitation of severely injured patients has shifted over the last decade toward less crystalloids and more blood products. Helsinki University trauma center implemented the massive transfusion protocol in the end of 2009. The aim of the study was to review the changes in fluid resuscitation and its influence on outcome of severely injured patients with hemodynamic compromise treated at the single tertiary trauma center.

MATERIAL AND METHODS

Data on severely injured patients (New Injury Severity Score > 15) from Helsinki University Hospital trauma center's trauma registry was reviewed over 2006-2013. The isolated head-injury patients, patients without hemodynamic compromise on admission (systolic blood pressure > 90 or base excess > -5.0), and those transferred in from another hospital were excluded. The primary outcome measure was 30-day in-hospital mortality. The study period was divided into three phases: 2006-2008 (pre-protocol, 146 patients), 2009-2010 (the implementation of massive transfusion protocol, 85 patients), and 2011-2013 (post massive transfusion protocol, 121 patients). Expected mortality was calculated using the Revised Injury Severity Classification score II. The Standardized Mortality Ratio, as well as the amounts of crystalloids, colloids, and blood products (red blood cells, fresh frozen plasma, platelets) administered prehospital and in the emergency room were compared.

RESULTS

Of the 354 patients that were included, Standardized Mortality Ratio values decreased (indicating better survival) during the study period from 0.97 (pre-protocol), 0.87 (the implementation of massive transfusion protocol), to 0.79 (post massive transfusion protocol). The amount of crystalloids used in the emergency room decreased from 3870 mL (pre-protocol), 2390 mL (the implementation of massive transfusion protocol), to 2340 mL (post massive transfusion protocol). In these patients, the blood products' (red blood cells, fresh frozen plasma, and platelets together) relation to crystalloids increased from 0.36, 0.70, to 0.74, respectively, in three phases.

CONCLUSION

During the study period, no other major changes in the protocols on treatment of severely injured patients were implemented. The overall awareness of damage control fluid resuscitation and introduction of massive transfusion protocol in a trauma center has a significant positive effect on the outcome of severely injured patients.

Trauma registry comparison: six-year results in trauma care in Southern Finland and Germany

PURPOSE

To compare the treatment and survival of trauma patients in Germany and Southern Finland.

METHODS

Data from Helsinki University Hospital trauma registry (TR-THEL) and TraumaRegister DGU(®) (TR-DGU) were compared in a period from 2006 until 2011. From TR-DGU level-one trauma centers treating annually >50 injury severity score (ISS) >15 patients were included. The inclusion criterion was ISS >15. Patients under 16 years with penetrating trauma without head injury and transferred in with isolated head injury were excluded. The compared parameters were age, sex, pre-injury ASA, injury scoring, injury pattern, mechanism of injury, injury distribution, pre-hospital timings, transportation method, pre-hospital intubation, treatment at hospital, discharge destination, and 30-day hospital mortality. Expected mortality was defined with the Revised Injury Severity Classification score (RISC).

RESULTS

Eighty-five German level-one trauma centers were included. A total of 15,306 and 1,274 patients were included in the outcome analysis from TR-DGU and TR-THEL, respectively. The difference between the observed and expected mortality of all patients was -4.1% (standardized mortality ratio [SMR] 0.82) at German hospitals and -4.0% (SMR 0.79) in Helsinki. Differences in the pre- and in-hospital treatment between the two countries were noted (transportation method, intubation rate, intensive care unit treatment, ventilation time, length of stay).

CONCLUSION

The overall outcome results of the Helsinki University Hospital trauma unit were similar to those of the German level-one trauma centers. Registry comparison is a feasible method of quality control in a trauma centre.

Reactivity of metal oxide clusters with hydrogen peroxide and water--a DFT study evaluating the performance of different exchange-correlation functionals

We have performed a density functional theory (DFT) investigation of the interactions of H2O2, H2O and HO radicals with clusters of ZrO2, TiO2 and Y2O3. Different modes of H2O adsorption onto the clusters were studied. In almost all the cases the dissociative adsorption is more exothermic than molecular adsorption. At the surfaces where H2O has undergone dissociative adsorption, the adsorption of H2O2 and the transition state for its decomposition are mediated by hydrogen bonding with the surface HO groups. Using the functionals B3LYP, B3LYP-D and M06 with clusters of 26 and 8 units of ZrO2, the M06 functional performed better than B3LYP in describing the reaction of decomposition of H2O2 and the adsorption of H2O. Additionally, we investigated clusters of the type (ZrO2)2, (TiO2)2 and (Y2O3) and the performance of the functionals B3LYP, B3LYP-D, B3LYP*, M06, M06-L, PBE0, PBE and PWPW91 in describing H2O2, H2O and HO˙ adsorption and the energy barrier for decomposition of H2O2. The trends obtained for HO˙ adsorption onto the clusters are discussed in terms of the ionization energy of the metal cation present in the oxide. In order to correctly account for the existence of an energy barrier for the decomposition of H2O2, the functional used must include Hartree-Fock exchange. Using minimal cluster models, the best performance in describing the energy barrier for H2O2 decomposition was obtained with the M06 and PBE0 functionals - the average absolute deviations from experiments are 6 kJ mol(-1) and 5 kJ mol(-1) respectively. With the M06 functional and a larger monoclinic (ZrO2)8 cluster model, the performance is in excellent agreement with experimental data. For the different oxides, PBE0 was found to be the most effective functional in terms of performance and computational time cost.

Utilizing the σ-complex stability for quantifying reactivity in nucleophilic substitution of aromatic fluorides

A computational approach using density functional theory to compute the energies of the possible σ-complex reaction intermediates, the “σ-complex approach”, has been shown to be very useful in predicting regioselectivity, in electrophilic as well as nucleophilic aromatic substitution. In this article we give a short overview of the background for these investigations and the general requirements for predictive reactivity models for the pharmaceutical industry. We also present new results regarding the reaction rates and regioselectivities in nucleophilic substitution of fluorinated aromatics. They were rationalized by investigating linear correlations between experimental rate constants (k) from the literature with a theoretical quantity, which we call the sigma stability (SS). The SS is the energy change associated with formation of the intermediate σ-complex by attachment of the nucleophile to the aromatic ring. The correlations, which include both neutral (NH₃) and anionic (MeO⁻) nucleophiles are quite satisfactory (r = 0.93 to r = 0.99), and SS is thus useful for quantifying both global (substrate) and local (positional) reactivity in S_NAr reactions of fluorinated aromatic substrates. A mechanistic analysis shows that the geometric structure of the σ-complex resembles the rate-limiting transition state and that this provides a rationale for the observed correlations between the SS and the reaction rate.

Computational design of a Diels-Alderase from a thermophilic esterase: the importance of dynamics

A novel computational Diels-Alderase design, based on a relatively rare form of carboxylesterase from Geobacillus stearothermophilus, is presented and theoretically evaluated. The structure was found by mining the PDB for a suitable oxyanion hole-containing structure, followed by a combinatorial approach to find suitable substrates and rational mutations. Four lead designs were selected and thoroughly modeled to obtain realistic estimates of substrate binding and prearrangement. Molecular dynamics simulations and DFT calculations were used to optimize and estimate binding affinity and activation energies. A large quantum chemical model was used to capture the salient interactions in the crucial transition state (TS). Our quantitative estimation of kinetic parameters was validated against four experimentally characterized Diels-Alderases with good results. The final designs in this work are predicted to have rate enhancements of ≈ 10(3)-10(6) and high predicted proficiencies. This work emphasizes the importance of considering protein dynamics in the design approach, and provides a quantitative estimate of the how the TS stabilization observed in most de novo and redesigned enzymes is decreased compared to a minimal, 'ideal' model. The presented design is highly interesting for further optimization and applications since it is based on a thermophilic enzyme (T (opt) = 70 °C).

Stepwise Diels-Alder: more than just an oddity? A computational mechanistic study

We have employed hybrid DFT and SCS-MP2 calculations at the SMD-PCM-6-311++G(2d,2p)//6-31+G(d) level to investigate the relationship between three possible channels for forming a Diels-Alder adduct from a highly nucleophilic diene and moderately to highly electrophilic dienophiles. We discuss geometries optimized using the B3LYP and M06-2X functionals with the 6-31+(d) basis set. The transition states and intermediates are characterized on the basis of geometric and electronic properties, and we also address the possibility of predicting detectability of a zwitterionic intermediate based on its relative stability. Our results show that a conventional Diels-Alder transition state conformation yields intermediates in all four investigated cases, but that these are too short-lived to be detected experimentally for the less activated reactants. The stepwise trans pathway, beginning with a conjugate addition-like transition state, becomes increasingly competitive with more activated reactants and is indeed favored for the most electrophilic dienophiles. Addition of a trans diene leads to a dead-end as the trans intermediates have insurmountable rotation barriers that prohibit formation of the second bond, unless another, heterocyclic intermediate is formed. We also show that introduction of a hydrogen bond donating catalyst favors a stepwise pathway even for less activated dienophiles.

Envisioning an enzymatic Diels-Alder reaction by in situ acid-base catalyzed diene generation

We present and evaluate a new and potentially efficient route for enzyme-mediated Diels-Alder reactions, utilizing general acid-base catalysis. The viability of employing the active site of ketosteroid isomerase is demonstrated.

Predicting regioselectivity in nucleophilic aromatic substitution

We have investigated practical and computationally efficient methods for the quantitative prediction of regioisomer distribution in kinetically controlled nucleophilic aromatic substitution reactions. One of the methods is based on calculating the relative stabilities of the isomeric σ-complex intermediates using DFT. We show that predictions from this method can be used quantitatively both for anionic nucleophiles with F(-) as leaving group, as well as for neutral nucleophiles with HF as leaving group. The σ-complex approach failed when the leaving group was Cl/HCl or Br/HBr, both for anionic and neutral nucleophiles, because of difficulties in finding relevant σ-complex structures. An approach where we assumed a concerted substitution step and used such transition state structures gave quantitatively useful results. Our results are consistent with other theoretical works, where a stable σ-complex has been identified in some cases, whereas others have been indicated to proceed via a concerted substitution step.

Designing a new Diels-Alderase: a combinatorial, semirational approach including dynamic optimization

A computationally inexpensive design strategy involving 'semirational' screening for enzymatic catalysis is presented. The protocol is based on well-established computational methods and represents a holistic approach to the catalytic process. The model reaction studied here is the Diels-Alder, for which a successful computational design has recently been published (Siegel, J. B. et al. Science 2010, 329, 309-313). While it is a leap forward in the field of computational design, the focus on designing only a small fraction of the active site gives little control over dynamics. Our approach explicitly incorporates mutagenesis and the analysis of binding events and transition states, and a promising enzyme-substrate candidate is generated with relatively little effort. We estimate catalytic rate accelerations of up to 10⁵.

pH-dependent mutarotation of 1-thioaldoses in water. Unexpected behavior of (2s)-D-aldopyranoses

The pH-dependent mutarotation of 1-thioaldopyranoses in aqueous media has been investigated. Anomerization readily occurred at lower and neutral pH for all aldopyranoses studied, whereas mainly for (2S)-D-aldopyranoses at higher pH. 1-Thio-D-mannopyranose and 1-thio-D-altropyranose showed very strong pH dependence where the anomeric equilibrium ratios changed dramatically from a preference for the β-anomer at lower pH to the α-anomer at higher pH.