On-the-Scene Hyaluronan and Syndecan-1 Serum Concentrations and Outcome after Cardiac Arrest and Resuscitation.

BACKGROUND: It is not predictable which patients will develop a severe inflammatory response after successful cardiopulmonary resuscitation (CPR), also known as "postcardiac arrest syndrome." This pathology affects only a subgroup of cardiac arrest victims. Whole body ischemia/reperfusion and prolonged shock states after return of spontaneous circulation (ROSC) may both contribute to this devastating condition. The vascular endothelium with its glycocalyx is especially susceptible to initial ischemic damage and may play a detrimental role in the initiation of postischemic inflammatory reactions. It is not known to date if an immediate early damage to the endothelial glycocalyx, detected by on-the-scene blood sampling and measurement of soluble components (hyaluronan and syndecan-1), precedes and predicts multiple organ failure (MOF) and survival after ROSC. METHODS: 15 patients after prehospital resuscitation were included in the study. Serum samples were collected on the scene immediately after ROSC and after 6 h, 12 h, 24 h, and 48 h. Hyaluronan and syndecan-1 were measured by ELISA. We associated the development of multiple organ failure and 30-day survival rates with these serum markers of early glycocalyx damage. RESULTS: Immediate serum hyaluronan concentrations show significant differences depending on 30-day survival. Further, the hyaluronan level is significantly higher in patients developing MOF during the initial and intermediate resuscitation period. Also, the syndecan-1 levels are significantly different according to MOF occurrence. CONCLUSION: Serum markers of glycocalyx shedding taken immediately on the scene after ROSC can predict the occurrence of multiple organ failure and adverse clinical outcome in patients after cardiac arrest.

[Arthroscopic repair of chronic lateral ankle instability]. / Arthroskopische Außenbandstabilisierung bei chronischer Instabilität des Sprunggelenks.

OBJECTIVE: Repair of the lateral ligament complex of the ankle joint; identification and treatment of intra-articular pathologies. INDICATIONS: Symptomatic chronic lateral ankle instability. Treatment of osteochondral lesions associated with lateral ankle instability. CONTRAINDICATIONS: Osteoarthritis of the ankle joint, risk factors such as peripheral occlusive disease, diabetic foot syndrome, complex regional pain syndrome. SURGICAL TECHNIQUE: Diagnostic arthroscopy of the ankle joint utilizing anterolateral and -medial portals; identification and treatment of intra-articular pathologies; identification and preparation of the distal fibula; insertion of two suture anchors; the sutures are passed inside-out through the joint capsule, the scarred lateral ligaments, the extensor retinaculum using a suture lasso; by tying down the sutures the tissue grasped is then pulled against the distal fibula; this will stabilize the lateral ligament complex. POSTOPERATIVE MANAGEMENT: Partial weight-bearing and short leg cast for 2 weeks, then 4 weeks ankle brace and range of motion exercises, thereafter functional physical therapy, ankle brace only during exercises; no sports for at least 3 months. RESULTS: Currently, one randomized controlled trial is available comparing open to arthroscopic lateral ankle ligament repair. Open repair was always combined with arthroscopy to treat intra-articular pathologies. In all patients, surgery led to a significant increase of the American Orthopaedic Foot and Ankle Score (AOFAS), Karlsson Score and visual analog score (VAS), but no significant differences between the open and arthroscopic procedure after one year with similar complications (arthroscopy group: 3 temporary nerve irritations and 2 patients with pain over the knot; open treated group: 2 temporary nerve irritations and one abscess). Intra-articular pathologies were treated in 68% of the arthroscopically treated patients and 70% of the patients treated by open surgery. One out of two retrospective comparative studies reported a significantly shorter operation time and time to return to daily activity and significantly lower VAS three days postoperatively for arthroscopically treated patients, while the other parameters assessed were comparable.

[Influence of massive blood transfusion and traumatic brain injury on TIMP­1 and MMP­9 serum levels in polytraumatized patients]. / Der Einfluss von Massentransfusion und Schädel-Hirn-Trauma auf die Seruminflammationsmarker TIMP­1 und MMP­9 bei polytraumatisierten Patienten.

BACKGROUND: The morbidity and mortality of polytrauma patients are substantially influenced by the extent of the posttraumatic inflammatory reaction. Studies have shown that TIMP­1 and MMP­9 play a major role in posttraumatic immune disorder in genome-wide mRNA microarray analyses. Furthermore, both showed differential gene expression profiles depending on the clinical parameters massive blood transfusion and traumatic brain injury. OBJECTIVE: The aim of this study was to evaluate TIMP­1 and MMP­9 serum concentrations in polytraumatized patients depending on the clinical parameters massive blood transfusion and traumatic brain injury in the early posttraumatic phase. MATERIAL AND METHODS: Polytrauma patients (≥18 years) with an "Injury Severity Score" (ISS) ≥ 16 points were enrolled in this prospective study. Serum levels of TIMP­1 and MMP­9 were quantified (at 0 h, 6 h, 12 h, 24 h, 48 h and 72 h) using an enzyme-linked immunosorbent assay (ELISA). Groups were divided according to the clinical parameter massive blood transfusion (≥10 red blood cell units [RBC units] in the first 24-hour posttrauma) and traumatic brain injury (CCT postive [cranial computed tomography]). RESULTS: Following massive blood transfusion (n = 21; 50 ± 15.7 years; ISS 39 ± 12.8 points) patients showed overall significantly increased TIMP­1 levels (p = 0.003) and significantly higher TIMP­1 values after 12-72 h. Traumatic brain injury patients (n = 28; 44 ± 19 years; ISS 42 ± 10 points) showed significantly higher MMP­9 levels (p = 0.049) in the posttraumatic period. CONCLUSION: Polytraumatized patients who received massive blood transfusions following major trauma showed significantly higher TIMP­1 levels than patients who did not receive massive transfusions. This seems to be an expression of a massively excessive inflammatory reaction and therefore represents a substantial factor in the pathogenesis of severe posttraumatic immune dysfunction in this collective. Furthermore, the significant increase in MMP­9 with accompanying traumatic brain injury reflects the pivotal role of matrix metalloproteinases in the pathophysiology of traumatic brain injury.

Initial free cortisol dynamics following blunt multiple trauma and traumatic brain injury: A clinical study.

OBJECTIVE: To determine free and total cortisol serum concentrations in the first 24 h after trauma and to evaluate the influence of traumatic brain injury (TBI) on their dynamics. METHODS: This prospective cohort study enrolled patients who had experienced multiple trauma and were admitted to a level 1 trauma centre. The patients were divided in two groups based on the presence of TBI according to clinical and radiological findings. Blood was collected initially as well as at 12 h and 24 h after the traumatic injury. Total cortisol, corticosteroid binding globulin (CBG) and free cortisol levels were determined. RESULTS: The study analysed data from 49 patients (36 males and 13 females) with a mean ± SD age of 45.0 ± 16.0 years. Of these, 36 presented with TBI and 13 had multiple injuries without TBI. Patients with TBI showed significantly lower concentrations of total cortisol and free cortisol compared with patients without TBI. Repeated measures analysis revealed different concentration dynamics in patients with TBI, with no increase in cortisol after trauma. CONCLUSION: Multiple trauma patients with TBI are at risk of acute impaired cortisol secretion and show an attenuated stress response as early as 12 h after injury.

[Fractures of the base of the V metatarsal bone-current concepts revised]. / Frakturen der Metatarsale Fünf Basis ­ eine Neubetrachtung.

Fractures of the base of the fifth metatarsal bone are one of the most frequent fractures to the foot and ankle. Despite the high frequency and although a number of studies are now available, treatment frequently does not follow the available evidence. Among the reasons is the inconsistent terminology used and that the studies available are neglected. The aim of this review is to present the current classifications, the available treatment studies and to derive evidence-based treatment recommendations. The term "Jones fracture" has been used inconsistently for different fracture entities and should, therefore, not be used anymore. Fractures are mostly classified according to Lawrence and Botte into three zones. However, the available studies demonstrate that type I and type II fractures according to Lawrence and Botte do not differ with respect to the prognosis. Both fractures can be successfully healed by functional treatment with weightbearing as tolerated. Consequently, a differentiation between these two zones does not seem to be meaningful. Therefore, they should be summarized as epi-metaphyseal fractures. Even dislocated, intra-articular, and multifragmentary fractures in this region can be functionally treated with good results. Fractures in the meta-diaphyseal region (Lawrence and Botte type III, distal to the IV and V intermetatarsal articulation) demonstrate a high rate of symptomatic non-unions after conservative treatment. Therefore, these fractures should be primarily treated operatively by closed reduction and intramedullary screw fixation.

[Insertional Achilles tendinopathy : Differentiated diagnostics and therapy]. / Ansatznahe Erkrankungen der Achillessehne : Differenzierte Diagnostik und Therapie.

Achilles tendinopathy at the calcaneal insertion is classified into insertional tendinopathy, retrocalcaneal and superficial bursitis. The aim of this study was to present the current evidence on conservative and surgical treatment of insertional tendinopathy of the Achilles tendon. Conservative first-line therapy includes reduction of activity levels, administration of non-steroidal anti-inflammatory drugs (NSAID), adaptation of footwear, heel wedges and orthoses or immobilization. In addition, further conservative therapy options are also available. Eccentric stretching exercises should be integral components of physiotherapy and can achieve a 40% reduction in pain. Extracorporeal shock wave therapy has been shown to reduce pain by 60% with a patient satisfaction of 80%. Due to the limited evidence, injections with platelet-rich plasma (PRP), dextrose (prolotherapy) or polidocanol (sclerotherapy) cannot currently be recommended. Operative therapy is indicated after 6 months of unsuccessful conservative therapy. Open debridement allows all pathologies to be addressed, including osseous abnormalities and intratendinous necrosis. The success rate of over 70% is contrasted by complication rates of up to 40%. The Achilles tendon should be reattached, if detached by >50%. No valid data are available for the transfer of the tendon of the flexor hallucis longus (FHL) muscle but it is frequently applied in cases of more than 50% debridement of the diameter of the Achilles tendon. Lengthening of the gastrocnemius muscle cannot be recommended because insufficient data are available. Tendoscopy is a promising treatment option for isolated retrocalcaneal bursitis and has shown similar success rates to open debridement with significantly lower complication rates.

[Acute achilles tendon rupture : State of the art]. / Die akute Achillessehnenruptur : Wo stehen wir heute?

The most favorable treatment for acute Achilles tendon ruptures remains controversial. In particular, three key questions are intensively debated: is operative or non-operative treatment superior? If surgery is performed, should open or minimally invasive percutaneous techniques be used? How should the follow-up treatment be carried out? The aim of this article is to answer these essential questions based on the currently available evidence. Non-operative treatment leads to a higher rate of re-ruptures and inferior functional results when compared to operative treatment. The major disadvantage of open surgery is the increased risk of wound healing problems and wound infections. Due to the development of minimally invasive percutaneous techniques, complication rates could be significantly reduced and patient satisfaction could be significantly improved, without increasing the risk of re-ruptures. The functional outcome is still partially unsatisfactory independent of the type of treatment. This is particularly expressed in weakness of the gastrocnemius-soleus muscle complex; therefore, the follow-up treatment is of fundamental importance. The available evidence clearly underlines the importance of early weight bearing and mobilization of the ankle joint, as it is safe and leads to better function, patient satisfaction and faster return to work or sport, compared with partial weight bearing and immobilization. Nevertheless, treatment protocols vary greatly with the majority still carrying out open suture and immobilizing follow-up treatment with fixed plantar flexion. Based on the available data the authors recommend minimally invasive percutaneous suture of the tendon followed by progressive functional rehabilitation. Implementation of the available evidence into routine practice is the next important step for successful treatment of this challenging injury.

The EXIT Strategy: an Approach for Identifying Bacterial Proteins Exported during Host Infection.

Exported proteins of bacterial pathogens function both in essential physiological processes and in virulence. Past efforts to identify exported proteins were limited by the use of bacteria growing under laboratory (in vitro) conditions. Thus, exported proteins that are exported only or preferentially in the context of infection may be overlooked. To solve this problem, we developed a genome-wide method, named EXIT (exported in vivotechnology), to identify proteins that are exported by bacteria during infection and applied it to Mycobacterium tuberculosis during murine infection. Our studies validate the power of EXIT to identify proteins exported during infection on an unprecedented scale (593 proteins) and to reveal in vivo induced exported proteins (i.e., proteins exported significantly more during in vivo infection than in vitro). Our EXIT data also provide an unmatched resource for mapping the topology of M. tuberculosis membrane proteins. As a new approach for identifying exported proteins, EXIT has potential applicability to other pathogens and experimental conditions.IMPORTANCE There is long-standing interest in identifying exported proteins of bacteria as they play critical roles in physiology and virulence and are commonly immunogenic antigens and targets of antibiotics. While significant effort has been made to identify the bacterial proteins that are exported beyond the cytoplasm to the membrane, cell wall, or host environment, current methods to identify exported proteins are limited by their use of bacteria growing under laboratory (in vitro) conditions. Because in vitro conditions do not mimic the complexity of the host environment, critical exported proteins that are preferentially exported in the context of infection may be overlooked. We developed a novel method to identify proteins that are exported by bacteria during host infection and applied it to identify Mycobacterium tuberculosis proteins exported in a mouse model of tuberculosis.

A dry powder combination of pyrazinoic acid and its n-propyl ester for aerosol administration to animals.

Combining the advantage of higher efficacy due to local pulmonary administration of pyrazinoic acid (POA) and potent effect of pyrazinoic acid ester (PAE) delivered as an aerosol would aid in tuberculosis therapy. A combination spray dried dry powder, composed of POA, PAE (n-propyl POA), maltodextrin and leucine, was prepared for aerosol delivery to animals. Solid-state characteristics of morphology (scanning electron microscopy) crystallinity (X-ray powder diffraction), thermal properties (thermogravimetric analysis and differential scanning calorimetry) and moisture content (Karl Fisher) were evaluated. Particle size distributions, by volume (laser diffraction) for the dispersed powder and by mass (inertial impaction) were determined. Efficient delivery of the powder to a nose only animal exposure chamber employed a novel rotating brush/micro-fan apparatus. Spherical, crystalline particles were prepared. The volume median diameter, ∼1.5µm, was smaller than the mass median aerodynamic diameter, ∼3.0µm, indicating modest aggregation. Drug content variations were observed across the particle size distribution and may be explained by PAE evaporative losses. Delivery to the nose-only exposure chamber indicated that boluses could be administered at approximately 3min intervals to avoid aerosol accumulation and effect uniform dose delivery with successive doses suitable for future pharmacokinetic and pharmacodynamic studies.

[Arthroscopic tibiotalocalcaneal arthrodesis]. / Arthroskopische Rückfußkorrekturarthrodese.

Tibiotalocalcaneal arthrodesis (TTCA) is indicated for a variety of disorders, including end-stage osteoarthritis, severe deformities and complications after operative interventions on the upper and lower ankle joints. Due to the biomechanical advantages, TTCA is predominantly performed with curved retrograde intramedullary nails allowing compression before locking. Hindfoot arthrodesis is most commonly performed by extensive open surgical approaches. Despite a patient satisfaction rate greater than 80 %, current reviews have reported mean complication rates of more than 50 % with a pronounced variance in bone union rates. This is influenced by the sometimes severe preexisting diseases in this patient collective. A predictive risk assessment for complications following TTCA revealed a significantly increased risk in the presence of diabetes mellitus, revision surgery or preoperative ulceration. In these high-risk patients, a reduction of the invasiveness of the procedure could possibly reduce the complication rates. Arthroscopic TTCA therefore appears to be a promising alternative approach. Even though only few case reports and one case series have been published, in the total collective of 17 patients only one subtalar non-union and one minor complication were reported. Despite the limited evidence available, arthroscopic TTCA appears to be a promising therapy option in patients with an increased risk profile and comorbidities, such as critical soft tissue situations, plantar ulceration, peripheral arterial occlusive disease (PAOD) and diabetes mellitus.

[Arthroscopically assisted treatment of ankle fractures]. / Arthroskopisch assistierte Frakturversorgung am oberen Sprunggelenk.

Acute ankle fractures are one of the most common fractures in adults with an incidence of 0.1-0.2 % per year. Operative treatment by open reduction and internal fixation (ORIF) is the standard method of treatment for unstable or dislocated fractures. The main goal of the operation is the anatomical realignment of the joint and restoration of ankle stability; nevertheless, anatomical reduction does not automatically lead to favorable clinical results. According to several studies the mid-term and in particular the long-term outcome following operative treatment is often poor with residual symptoms including chronic pain, stiffness, recurrent swelling and ankle instability. There is growing evidence that this poor outcome might be related to occult intra-articular injuries involving cartilage and soft tissues. In recent studies the frequency of fracture-related osteochondral lesions was reported to be approximately 64 %. By physical examination, standard radiography or even computed tomography (CT), these intra-articular pathologies cannot be reliably diagnosed; therefore, many authors emphasize the value of ankle arthroscopy in acute fracture treatment as it has become a safe and effective diagnostic and therapeutic procedure. Arthroscopically assisted open reduction and internal fixation (AORIF) allows control of the reduction as well examination of all intra-articular structures. If necessary, intra-articular pathologies can be addressed by removing ruptured ligaments and loose bodies, performing chondroplasty or microfracturing. So far there is no evidence that supplementary ankle arthroscopy increases the complication rate. On the other hand, the positive effect of AORIF has also not been clearly documented; nevertheless, there are clear indications that arthroscopically assisted fracture treatment is beneficial, especially in complex fractures.

Classical collision spectrum of O + CO.

The work of Noid et al. [ J. Chem. Phys. 1977 , 67 , 404 ] has shown that sharp molecular spectra can be obtained through a Fourier transform of the autocorrelation function of a classical trajectory. In the present work, we extend this idea to obtain a spectrum by Fourier transform of the dipole moment function of collision product trajectories. We show that this "classical collision spectrum" (CCS) is related to the cross section for creating the product times an Einstein A factor. As a test case, we analyze product CO trajectories obtained from O + CO collisions at 8 km/s and focus on the spectral resolution of the CCS. The CCS of these trajectories shows rich quantum-like features, including well-separated vibrational overtones and rotational band heads, which become more pronounced with particular trajectory weighting methods. For polyatomic cases, the hope is that the CCS can be deconvolved into ro-vibrational specific probabilities and cross sections for quasi-periodic trajectories, which would otherwise overlap in a conventional classical trajectory energy analysis. Chaotic trajectories are expected to broaden and decrease the achievable resolution of the CCS. Chaotic motion will therefore impact the ability to separate ro-vibrational specific cross sections, an issue that will be addressed in future work.

The impact of chemokine receptor CX3CR1 deficiency during respiratory infections with Mycobacterium tuberculosis or Francisella tularensis.

Recruitment of immune cells to infection sites is a critical component of the host response to pathogens. This process is facilitated partly through interactions of chemokines with cognate receptors. Here, we examine the importance of fractalkine (CX3CL1) receptor, CX3CR1, which regulates function and trafficking of macrophages and dendritic cells, in the host's ability to control respiratory infections with Mycobacterium tuberculosis or Francisella tularensis. Following low-dose aerosol challenge with M. tuberculosis, CX3CR1(-/-) mice were no more susceptible to infection than wild-type C57BL/6 mice as measured by organ burden and survival time. Similarly, following inhalation of F. tularensis, CX3CR1(-/-) mice displayed similar organ burdens to wild-type mice. CX3CR1(-/-) mice had increased recruitment of monocytes and neutrophils in the lung; however, this did not result in increased abundance of infected monocytes or neutrophils. We conclude that CX3CR1-deficiency affects immune-cell recruitment; however, loss of CX3CR1 alone does not render the host more susceptible to M. tuberculosis or F. tularensis.

Identification of biomarkers for the antiangiogenic and antitumour activity of the superoxide dismutase 1 (SOD1) inhibitor tetrathiomolybdate (ATN-224).

Tetrathiomolybdate (choline salt; ATN-224), a specific, high-affinity copper binder, is currently being evaluated in several phase II cancer trials. ATN-224 inhibits CuZn superoxide dismutase 1 (SOD1) leading to antiangiogenic and antitumour effects. The pharmacodynamics of tetrathiomolybdate has been followed by tracking ceruloplasmin (Cp), a biomarker for systemic copper. However, at least in mice, the inhibition of angiogenesis occurs before a measurable decrease in systemic copper is observed. Thus, the identification and characterisation of other biomarkers to follow the activity of ATN-224 in the clinic is of great interest. Here, we present the preclinical evaluation of two potential biomarkers for the activity of ATN-224: (i) SOD activity measurements in blood cells in mice and (ii) levels of endothelial progenitor cells (EPCs) in bonnet macaques treated with ATN-224. The superoxide dismutase activity in blood cells in mice is rapidly inhibited by ATN-224 treatment at doses at which angiogenesis is maximally inhibited. Furthermore, ATN-224 dosing in bonnet macaques causes a profound and reversible decrease in EPCs without significant toxicity. Thus, both SOD activity measurements and levels of EPCs may be useful biomarkers of the antiangiogenic activity of ATN-224 to be used in its clinical development.

Potential surfaces and dynamics of the O(3P)+H2O(X1A1)-->OH(X2pi)+OH(X2pi) reaction.

We present global potential energy surfaces for the three lowest triplet states in O(3P)+H2O(X1A1) collisions and present results of classical dynamics calculations on the O(3P)+H2O(X1A1)-->OH(X2pi)+OH(X2pi) reaction using these surfaces. The surfaces are spline-based fits of approximately 20,000 fixed geometry ab initio calculations at the complete-active-space self-consistent field+second-order perturbation theory (CASSCF+MP2) level with a O(4s3p2d1f)/H(3s2p) one electron basis set. Computed rate constants compare well to measurements in the 1000-2500 K range using these surfaces. We also compute the total, rovibrationally resolved, and differential angular cross sections at fixed collision velocities from near threshold at approximately 4 km s(-1) (16.9 kcal mol(-1) collision energy) to 11 km s(-1) (122.5 kcal mol(-1) collision energy), and we compare these computed cross sections to available space-based and laboratory data. A major finding of the present work is that above approximately 40 kcal mol(-1) collision energy rovibrationally excited OH(X2pi) products are a significant and perhaps dominant contributor to the observed 1-5 micro spectral emission from O(3P)+H2O(X1A1) collisions. Another important result is that OH(X2pi) products are formed in two distinct rovibrational distributions. The "active" OH products are formed with the reagent O atom, and their rovibrational distributions are extremely hot. The remaining "spectator" OH is relatively rovibrationally cold. For the active OH, rotational energy is dominant at all collision velocities, but the opposite holds for the spectator OH. Summed over both OH products, below approximately 50 kcal mol(-1) collision energy, vibration dominates the OH internal energy, and above approximately 50 kcal mol(-1) rotation is greater than vibrational energy. As the collision energy increases, energy is diverted from vibration to mostly translational energy. We note that the present fitted surfaces can also be used to investigate direct collisional excitation of H2O(X1A1) by O(3P) and also OH(X2pi)+OH(X2pi) collisions.

Quantum and quasiclassical studies of the O(3P)+HCl-->OH+Cl(2P) reaction using benchmark potential surfaces.

We have performed quantum mechanical (QM) dynamics calculations within the independent-state approximation with new benchmark triplet A" and A' surfaces [B. Ramachandran et al., J. Chem. Phys. 119, 9590 (2003)] for the rovibronic state-to-state measurements of the reaction O(3P)+HCl(v=2,j=1,6,9)-->OH(v'j')+Cl(2P) [Zhang et al., J. Chem. Phys. 94, 2704 (1991)]. The QM and experimental rotational distributions peak at similar OH(j') levels, but the QM distributions are significantly narrower than the measurements and previous quasiclassical dynamics studies. The OH(low j) populations observed in the measurements are nearly absent in the QM results. We have also performed quasiclassical trajectory with histogram binning (QCT-HB) calculations on these same benchmark surfaces. The QCT-HB rotational distributions, which are qualitatively consistent with measurements and classical dynamics studies using other surfaces, are much broader than the QM results. Application of a Gaussian binning correction (QCT-GB) dramatically narrows and shifts the QCT-HB rotational distributions to be in very good agreement with the QM results. The large QCT-GB correction stems from the special shape of the joint distribution of the classical rotational/vibrational action of OH products. We have also performed QM and QCT calculations for the transition, O+HCl(v=0,T=300 K)-->OH(v'j')+Cl from threshold to approximately 130 kcal mol(-1) collision energy as a guide for possible future hyperthermal O-atom measurements. We find in general a mixed energy release into translation and rotation consistent with a late barrier to reaction. Angular distributions at high collision energy are forward peaked, consistent with a stripping mechanism. Direct collisional excitation channel cross sections, O+HCl(v=0,T=300 K)-->O+HCl(v'=1), in the same energy range are large, comparable in magnitude to the reactive channel cross sections. Although the (3)A" state dominates most collision processes, above approximately 48 kcal mol(-1), the (3)A' state plays the major role in collisional excitation.

Measurements and simulations of high energy O(3P) + Ar(1S) angular scattering: single and multi-collision regimes.

We present differential angular cross sections for O(3P) + Ar(1S) scattering at collision energies near 90 kcal mol(-1) (approximately 8 km s(-1) relative velocity) from molecular beam measurements and high-level theoretical calculations. Beams of hyperthermal O(3P) are now being used to investigate novel gas-phase and gas-surface chemistries, and the comparison of theory and measurements on this simple system will be a stringent test of the experimental methodology. Potential energy curves were generated for O(3P) + Ar(1S) using a large cc-pVQZ basis within a valence multi-configuration plus perturbation theory treatment. These curves were then used in quantum scattering calculations to generate differential cross sections. Agreement between experiment and theory is excellent. In addition to these comparisons, the cross sections were used in direct simulation Monte Carlo calculations to investigate effects of increasing the Ar flux above the "single-collision" regime. As the Ar flux increases, the observed differential angular cross sections change in two ways. In addition to the main "single-scatter" peak along the incident O-atom beam direction, a secondary O-atom peak appears in the direction of the incident Ar beam, and the multiple-scattered O-atom translational energy starts to reflect the energy of the relatively slow moving Ar beam.

Quantum and classical studies of the O(3P) + H2(v = 0-3,j = 0) --> OH + H reaction using benchmark potential surfaces.

We present results of time-dependent quantum mechanics (TDQM) and quasiclassical trajectory (QCT) studies of the excitation function for O(3P) + H2(v = 0-3,j = 0) --> OH + H from threshold to 30 kcal/mol collision energy using benchmark potential energy surfaces [Rogers et al., J. Phys. Chem. A 104, 2308 (2000)]. For H2(v = 0) there is excellent agreement between quantum and classical results. The TDQM results show that the reactive threshold drops from 10 kcal/mol for v = 0 to 6 for v = 1, 5 for v = 2 and 4 for v = 3, suggesting a much slower increase in rate constant with vibrational excitation above v = 1 than below. For H2(v > 0), the classical results are larger than the quantum results by a factor approximately 2 near threshold, but the agreement monotonically improves until they are within approximately 10% near 30 kcal/mol collision energy. We believe these differences arise from stronger vibrational adiabaticity in the quantum dynamics, an effect examined before for this system at lower energies. We have also computed QCT OH(v',j') state-resolved cross sections and angular distributions. The QCT state-resolved OH(v') cross sections peak at the same vibrational quantum number as the H2 reagent. The OH rotational distributions are also quite hot and tend to cluster around high rotational quantum numbers. However, the dynamics seem to dictate a cutoff in the energy going into OH rotation indicating an angular momentum constraint. The state-resolved OH distributions were fit to probability functions based on conventional information theory extended to include an energy gap law for product vibrations.

Two nonredundant SecA homologues function in mycobacteria.

The proper extracytoplasmic localization of proteins is an important aspect of mycobacterial physiology and the pathogenesis of Mycobacterium tuberculosis. The protein export systems of mycobacteria have remained unexplored. The Sec-dependent protein export pathway has been well characterized in Escherichia coli and is responsible for transport across the cytoplasmic membrane of proteins containing signal sequences at their amino termini. SecA is a central component of this pathway, and it is highly conserved throughout bacteria. Here we report on an unusual property of mycobacterial protein export--the presence of two homologues of SecA (SecA1 and SecA2). Using an allelic-exchange strategy in Mycobacterium smegmatis, we demonstrate that secA1 is an essential gene. In contrast, secA2 can be deleted and is the first example of a nonessential secA homologue. The essential nature of secA1, which is consistent with the conserved Sec pathway, leads us to believe that secA1 represents the equivalent of E. coli secA. The results of a phenotypic analysis of a Delta secA2 mutant of M. smegmatis are presented here and also indicate a role for SecA2 in protein export. Based on our study, it appears that SecA2 can assist SecA1 in the export of some proteins via the Sec pathway. However, SecA2 is not the functional equivalent of SecA1. This finding, in combination with the fact that SecA2 is highly conserved throughout mycobacteria, suggests a second role for SecA2. The possibility exists that another role for SecA2 is to export a specific subset of proteins.