Ångstrom-Depth Resolution with Chemical Specificity at the Liquid-Vapor Interface

The determination of depth profiles across interfaces is of primary importance in many scientific and technological areas. Photoemission spectroscopy is in principle well suited for this purpose, yet a quantitative implementation for investigations of liquid-vapor interfaces is hindered by the lack of understanding of electron-scattering processes in liquids. Previous studies have shown, however, that core-level photoelectron angular distributions (PADs) are altered by depth-dependent elastic electron scattering and can, thus, reveal information on the depth distribution of species across the interface. Here, we explore this concept further and show that the experimental anisotropy parameter characterizing the PAD scales linearly with the average distance of atoms along the surface normal obtained by molecular dynamics simulations. This behavior can be accounted for in the low-collision-number regime. We also show that results for different atomic species can be compared on the same length scale. We demonstrate that atoms separated by about 1 Å along the surface normal can be clearly distinguished with this method, achieving excellent depth resolution.

Fampridine-induced changes in walking kinetics are associated with clinical improvements in patients with multiple sclerosis

Gait dysfunction is common in patients with multiple sclerosis (PwMS). Treatment with prolonged-release fampridine (PR-fampridine) improves walking ability in some PwMS. Associated fampridine-induced changes in the walking pattern are still poorly understood but may provide a better understanding of the mechanisms underlying the beneficial drug effects. 61 PwMS were treated with PR-fampridine in a randomized, monocentric, double-blind and placebo-controlled clinical trial with crossover design (FAMPKIN). Drug-induced improvements in walking speed (Timed-25-Foot Walk; T25FW) and endurance (6-Minute Walk Test; 6MWT) were quantified. In this sub-study of the FAMPKIN trial, fampridine-induced changes in kinetic gait patterns were analyzed by pressure-based foot print analysis during treadmill walking. Vertical ground reaction forces were analyzed during different gait phases. Kinetic data of 44 PwMS was eligible for analysis. During double-blind treatment with PR-fampridine, patients performed significantly better in the T25FW and 6MWT than during placebo treatment (p < 0.0001 for both). At the group level (n = 44), there were no significant changes of gait kinetics under PR-fampridine vs. placebo. However, we found relevant changes of walking kinetics regarding forces during loading, single limb and pre-swing phase in a patient sub-group (n = 8). Interestingly, this sub-group demonstrated superior responsiveness to PR-fampridine in the clinical walking tests compared to those patients without any fampridine-induced changes in kinetics (n = 36). Our results demonstrate fampridine-induced changes in gait kinetics in a sub-group of PwMS. These gait pattern changes were accompanied by improved clinical walking performance under PR-fampridine. These results shed some light on the biomechanical changes in walking patterns underlying enhanced fampridine-induced gait performance.

The Structure of VOPc on Cu(111): Does V=O Point Up, or Down, or Both?

The local structure of the nonplanar phthalocyanine, vanadyl phthalocyanine (VOPc), adsorbed on Cu(111) at a coverage of approximately one-half of a saturated molecular layer, has been investigated by a combination of normal-incidence X-ray standing waves (NIXSW), scanned-energy mode photoelectron diffraction (PhD), and density-functional theory (DFT), complemented by scanning tunnelling microscopy (STM). Qualitative assessment of the NIXSW data clearly shows that both "up" and "down" orientations of the molecule (with V=O pointing out of, and into, the surface) must coexist on the surface. O 1s PhD proves to be inconclusive regarding the molecular orientation. DFT calculations, using two different dispersion correction schemes, show good quantitative agreement with the NIXSW structural results for equal co-occupation of the two different molecular orientations and clearly favor the many body dispersion (MBD) method to deal with long-range dispersion forces. The calculated relative adsorption energies of the differently oriented molecules at the lowest coverage show a strong preference for the "up" orientation, but at higher local coverages, this energetic difference decreases, and mixed orientation phases are almost energetically equivalent to pure "up"-oriented phases. DFT-based Tersoff-Hamann simulations of STM topographs for the two orientations cast some light on the extent to which such images provide a reliable guide to molecular orientation.

Chemical shift reference scale for Li solid state NMR derived by first-principles DFT calculations

For studying electrode and electrolyte materials for lithium ion batteries, solid-state (SS) nuclear magnetic resonance (NMR) of lithium moves into focus of current research. Theoretical simulations of magnetic resonance parameters facilitate the analysis and interpretation of experimental Li SS-NMR spectra and provide unique insight into physical and chemical processes that are determining the spectral profile. In the present paper, the accuracy and reliability of the theoretical simulation methods of Li chemical shielding values is benchmarked by establishing a reference scale for Li SS-NMR of diamagnetic compounds. The impact of geometry, ionic mobility and relativity are discussed. Eventually, the simulation methods are applied to the more complex lithium titanate spinel (Li₄Ti₅O₁₂, LTO), which is a widely discussed battery anode material. Simulation of the Li SS-NMR spectrum shows that the commonly adopted approach of assigning the resonances to individual crystallographic sites is not unambiguous.

Synthesis of heteroatomic bridged paracyclophanes

Heteroatomic bridged paracyclophanes were obtained by two independent synthetic approaches. The required precursors consist of para R₂SiCl (R = Me, iPr) substituted aromatic rings (2 and 4). They were subsequently functionalised by using NH₃, [LiPH₂(dme)] or LiAl(PH₂)₄. In the case of the Me-substituted species 2, the reaction with NH₃ directly yielded the Si₂N bridged paracyclophane 5. The Si₂P incorporated derivative 10 was obtained by lithiation of p-C₆H₄(SiiPr₂PH₂)₂ (9) and subsequent salt metathesis with the chlorosilane 4. The second approach involves the use of GaEt₃ in the formation of four membered (GaPn)₂ cycles (Pn = N, P). p-[C₆H₄{SiiPr₂N(H)GaEt₂}₂]₂ (11) and p-[C₆H₄{SiiPr₂P(H)GaEt₂}₂]₂ (12) represent the first examples of stable (GaPn)₂cis isomers as the trans species did not appear in solution. Although 11 and 12 show a similar coordination pattern, they differ in the orientation of the aromatic systems: in the solid structure, 11 adopts a - for paracyclophanes so far unique - T-shape conformation of the phenyl rings, while 12 shows the predominant coplanar orientation. All cyclophanes were characterized by X-ray diffraction, elemental analysis, NMR and IR spectroscopy.

Consecutive reactions of small, free tantalum clusters with dioxygen controlled by relaxation dynamics

The reaction of small cationic tantalum clusters (Ta_n⁺, n = 4–8) with molecular oxygen is studied under multi-collision conditions in the gas phase, and the reaction kinetics are analyzed in order to elucidate underlying mechanisms.

Role of physisorption states in molecular scattering: a semilocal density-functional theory study on O2/Ag(111)

We simulate the scattering of O2 from Ag(111) with classical dynamics simulations performed on a six-dimensional potential energy surface calculated within semilocal density-functional theory. The enigmatic experimental trends that originally required the conjecture of two types of repulsive walls, arising from a physisorption and chemisorption part of the interaction potential, are fully reproduced. Given the inadequate description of the physisorption properties in semilocal density-functional theory, our work casts severe doubts on the prevalent notion to use molecular scattering data as indirect evidence for the existence of such states.

[Psycho-oncological care for melanoma patients: conception and implementation]

Offering psycho-oncological care is an essential, guideline-based component of comprehensive care in skin cancer centers. This paper describes the development, implementation and utilization of a specific psycho-oncologic care concept for melanoma patients in the University Dermatology Clinic Freiburg. Based on the stepped-care principle, the concept is composed of interdisciplinary group sessions for patients and their relatives offered every 4-6 weeks addressing medical and psycho-oncological topics related to treatment of malignant melanoma and then individual psycho-oncological sessions modified for the patient's treatment needs. Between April 2010 and July 2012, 67 % of the melanoma patients treated in the Freiburg Skin Cancer Center were reached by the program. A stepped-care concept with a routinely initiated first contact and low-threshold patient education group sessions is a reliable approach to reach patients and inform them about further psycho-oncological care. The advantages justify the allocation of resources and the approach proved successful for routine clinical practice.

In situ x-ray photoelectron spectroscopy of model catalysts: at the edge of the gap

We present high-pressure x-ray photoelectron spectroscopy (HP-XPS) and first-principles kinetic Monte Carlo study addressing the nature of the active surface in CO oxidation over Pd(100). Simultaneously measuring the chemical composition at the surface and in the near-surface gas phase, we reveal both O-covered pristine Pd(100) and a surface oxide as stable, highly active phases in the near-ambient regime accessible to HP-XPS. Surprisingly, no adsorbed CO can be detected during high CO(2) production rates, which can be explained by a combination of a remarkably short residence time of the CO molecule on the surface and mass-transfer limitations in the present setup.

Structure and energetics of azobenzene on Ag(111): benchmarking semiempirical dispersion correction approaches

We employ normal-incidence x-ray standing wave and temperature programed desorption spectroscopy to derive the adsorption geometry and energetics of the prototypical molecular switch azobenzene at Ag(111). This allows us to assess the accuracy of semiempirical correction schemes as a computationally efficient means to overcome the deficiency of semilocal density-functional theory with respect to long-range van der Waals (vdW) interactions. The obtained agreement underscores the significant improvement provided by the account of vdW interactions, with remaining differences mainly attributed to the neglect of electronic screening at the metallic surface.

Wave-driven dynamo action in spherical magnetohydrodynamic systems

Hydrodynamic and magnetohydrodynamic numerical studies of a mechanically forced two-vortex flow inside a sphere are reported. The simulations are performed in the intermediate regime between the laminar flow and developed turbulence, where a hydrodynamic instability is found to generate internal waves with a characteristic m=2 zonal wave number. It is shown that this time-periodic flow acts as a dynamo, although snapshots of the flow as well as the mean flow are not dynamos. The magnetic fields' growth rate exhibits resonance effects depending on the wave frequency. Furthermore, a cyclic self-killing and self-recovering dynamo based on the relative alignment of the velocity and magnetic fields is presented. The phenomena are explained in terms of a mixing of nonorthogonal eigenstates of the time-dependent linear operator of the magnetic induction equation. The potential relevance of this mechanism to dynamo experiments is discussed.

O- and H-induced surface core level shifts on Ru(0001): prevalence of the additivity rule

In previous work on adsorbate-induced surface core level shifts (SCLSs), the effects caused by O atom adsorption on Rh(111) and Ru(0001) were found to be additive: the measured shifts for first-layer Ru atoms depended linearly on the number of directly coordinated O atoms. Density-functional theory calculations quantitatively reproduced this effect, allowed separation of initial- and final-state contributions, and provided an explanation in terms of a roughly constant charge transfer per O atom. We have now conducted similar measurements and calculations for three well-defined adsorbate and coadsorbate layers containing O and H atoms: (1 × 1)-H, (2 × 2)-(O+H) and (2 × 2)-(O+3H) on Ru(0001). As H is stabilized in fcc sites in the prior two structures and in hcp sites in the latter, this enables us to not only study coverage and coadsorption effects on the adsorbate-induced SCLSs, but also the sensitivity to similar adsorption sites. Remarkably good agreement is obtained between experiment and calculations for the energies and geometries of the layers, as well as for all aspects of the SCLS values. The additivity of the next-neighbor adsorbate-induced SCLSs is found to prevail even for the coadsorbate structures. While this confirms the suggested use of SCLSs as fingerprints of the adsorbate configuration, their sensitivity is further demonstrated by the slightly different shifts unambiguously determined for H adsorption in either fcc or hcp hollow sites.

Executive control in obsessive-compulsive disorder: event-related potentials in a Go/Nogo task

Obsessive-compulsive disorder (OCD) has been related to a hyperactive cortico-striatal-pallidal-thalamic circuitry resulting clinically in an impaired inhibition of repetitive thoughts and behaviors. We examined thirteen patients with OCD and thirteen age-, sex-, and education matched healthy controls using event-related potentials (ERPs). Participants performed a hybrid flanker-Go/Nogo task while multichannel EEG was recorded. Our study focused on two ERP components: the Nogo-N2 and the Nogo-P3, which have been discussed in the context of response inhibition and response conflict. Artifact-free EEG-segments were used to compute ERPs on correct Go trials (button press) and correct Nogo trials (no button press), separately. Patients with OCD showed enhanced (more negative) Nogo-N2 amplitudes than controls, and a significant difference in amplitudes between Nogo-N2 and Go-N2 trials (more negative for Nogo trials) at central midline electrode positions. However, groups did not differ with regard to the Nogo-P3 and Go-P3. The present study replicates and extends previous findings of altered executive control processes in OCD patients.

Differences in prevalence rates of psychological distress and mental disorders in inpatients and outpatients with breast and gynaecological cancer

Research has demonstrated that in a significant number of patients, mental disorders occur with cancer. However, it is not known whether there is a difference for comorbidity in patients who are treated in hospitals versus outpatient care. The present study initially screened patients for psychological distress and quality of life with breast and gynaecological cancer. Instruments used were the General Health Questionnaire-12 and the Hospital Anxiety and Depression Scale, and for quality of life, the SF-36 Health Survey was used. In the next stage, a subsample of patients was assessed with standardized clinical interview (Composite International Diagnostic Interview) for the detection of mental disorders according to the Diagnostic and Statistical Manual of Mental Disorders, 4(th) Edn. The frequency of psychologically distressed patients in inpatient care is about 10% higher than in outpatient care. A higher risk (OR = 1.2-2.0) for mental disorders is found for inpatients compared with outpatients in all prevalence periods. Although differences in psychological distress, quality of life and prevalences of mental disorders failed to achieve statistical significance, the descriptive results indicate that inpatients with breast or gynaecological cancer suffer more often from psychological distress and comorbid mental disorders than outpatients. Outpatient treatment can therefore be considered as an important alternative to inpatient care, as patients with comparable disease severity adjust similarly or even better without full hospital care.

Revisiting the structure of the p(4 x 4) surface oxide on Ag(111)

Scanning tunneling microscopy (STM) and density-functional theory are used to reexamine the structure of the renowned p(4 x 4)-O/Ag(111) surface oxide. The accepted structural model [C. I. Carlisle, Phys. Rev. Lett. 84, 3899 (2000)10.1103/PhysRevLett.84.3899] is incompatible with the enhanced resolution of the current STM measurements. An "Ag6 model" is proposed that is more stable than its predecessor and accounts for the coexistence of the p(4 x 4) and a novel c(3 x 5log3)rect phase. This coexistence is an indication of the dynamic complexity of the system that until now has not been appreciated.

The concepts of fatigue and depression in cancer

A strong association between fatigue and depression in cancer patients has been reported repeatedly in clinical studies. The distinction remains difficult, mainly because of the similar phenomenology of fatigue and depression. It is the aim of this paper to work out similarities and differences in the conception of fatigue and depressive disorders. For that, a differentiation between depression as emotional distress and depression as clinical syndrome, according to the current classification systems, has to be made. Therefore, the classification of depressive disorders and their criteria is presented in the second section of this paper, especially in view of the diagnosis of depressive disorders in cancer patients. The comparison of the multidimensional fatigue construct and depression shows a strong overlap of symptoms. None of the fatigue symptoms are specific for fatigue, all being elements of depressive syndromes. It is in particular the psychological symptoms of depressive disorders that differentiate between the two concepts. To that end, the question is discussed whether fatigue in its current conceptualization can be defined as a diagnostic entity independent of depressive disorders. Additionally, research approaches are presented from the area of the chronic fatigue syndrome and neurasthenia, which could be adapted to cancer-related fatigue and help to clarify the clinical differences between fatigue and depression. In order to ensure better differential diagnostics in the future, criteria-orientated research in particular is needed.

Kinetic hindrance during the initial oxidation of Pd(100) at ambient pressures

The oxidation of the Pd(100) surface at oxygen pressures in the 10(-6) to 10(3) mbar range and temperatures up to 1000 K has been studied in situ by surface x-ray diffraction (SXRD). The results provide direct structural information on the phases present in the surface region and on the kinetics of the oxide formation. Depending on the (T,p) environmental conditions, we observe either a thin (sqrt[5]xsqrt[5])R27 degrees surface oxide or the growth of a rough, poorly ordered bulk oxide film of PdO predominantly with (001) orientation. By either comparison to the surface phase diagram from first-principles atomistic thermodynamics or by explicit time-resolved measurements we identify a strong kinetic hindrance to the bulk oxide formation even at temperatures as high as 675 K.

[Prevalence and risk factors of psychological burden and mental disorders in patients with musculoskeletal diseases -- a review of empirical studies]

A musculoskeletal disease frequently entails numerous physical, social and occupational limitations, e.g. reduction of physical capabilities, chronic pain, and loss of employment. A number of patients suffer from comorbid psychological strain or mental disorders, and it frequently remains unclear whether these psychological phenomena are unconnected to, a consequence of or even among the causes for the somatic disease. In order to diagnose, or possibly prevent, comorbid mental disorders, it is necessary to know risk factors which are associated with mental disorders. Studies published during the last twenty years are reviewed which examine sociodemographic, disease specific and psychosocial factors in connection with psychological strain or mental disorders among patients with musculoskeletal diseases. Due to the relatively small number of relevant studies (n = 12), the findings have to be interpreted carefully.

[Epidemiology of comorbid mental disorders in rehabilitation patients with musculosceletal and cardiovascular diseases]

An association between mental disorders, musculoskeletal and cardiovascular diseases has been reported in many clinical studies with inpatients. However, no data exist about the prevalence of mental disorders in patients undergoing rehabilitation treatment for musculoskeletal and cardiovascular diseases. The present study investigates 4-week, 12-month and lifetime prevalence rates of comorbid mental disorders in more than 1700 patients out of 10 rehabilitation clinics. The patients were screened (GHQ-12, HADS) in the context of a two-stage epidemiological survey. In the second-stage examination a subsample of 369 patients was interviewed with a standardized clinical interview (CIDI) in order to obtain DSM-IV and ICD-10 diagnoses of mental disorders. 43 % (musculoskeletal) and 36 % (cardiovascular) of the patients have high GHQ-scores (cut off > 4). Furthermore, up to 24 % of the musculoskeletal and cardiovascular patients have elevated scores on the HADS subscales depression and anxiety (cut off > 10). For the 4-week period, prevalence rates of mental disorders in the sample of patients with musculoskeletal diseases are 31 % and 20 % in the sample of patients with cardiovascular diseases. The most frequent current disorders are affective and anxiety disorders. The high psychosocial burden expressed by the patients and the prevalence of depressive and anxiety disorders emphasize the importance of (1) effective diagnostic strategies to recognize mental disorders, (2) specialized psychological services in rehabilitation clinics, which provide psychological support and effective interventions for patients with musculoskeletal and cardiovascular diseases.

Role of subsurface oxygen in oxide formation at transition metal surfaces

We present a density-functional theory trend study addressing the incorporation of oxygen into the basal plane of the late 4d transition metals (TMs) from Ru to Ag. Occupation of subsurface sites is always connected with a significant distortion of the host lattice, rendering it initially less favorable than on-surface chemisorption. Penetration starts only after a critical coverage theta(c), which is lower for the softer metals towards the right of the TM series. The computed theta(c) are found to be very similar to those above which the bulk oxide phase becomes thermodynamically more stable, thus suggesting that the initial incorporation of O actuates the formation of a surface oxide on TM surfaces.

Screening for anxiety, depressive and somatoform disorders in rehabilitation--validity of HADS and GHQ-12 in patients with musculoskeletal disease

PURPOSE

The detection of patients with comorbid mental illness is of high clinical importance in orthopaedic rehabilitation. To simplify detection of cases, screening instruments are recommended. The study investigated the discriminant validity of the Hospital Anxiety and Depression Scale (HADS) and the General Health Questionnaire (GHQ-12) to identify patients with comorbid mental disorders, specifically anxiety, depressive and somatoform disorders.

METHOD

Two hundred and six patients with musculoskeletal disease from four orthopaedic rehabilitation clinics participated in a two-stage survey: (1) patients were assessed with the GHQ-12 and HADS; and (2) they were examined for DSM-IV mental disorders by clinical standardized interview (CIDI). Validity of the two instruments regarding the detection of mental disorders was compared using ROC-analysis and CIDI-diagnoses as criteria.

RESULTS

The HADS sumscale performed better in all analyses compared to the GHQ-12, specifically in detecting depressive and anxiety disorders. Best results are achieved for depressive disorders with an area under the curve (AUC) of 0.79, a sensitivity of 78% and a specificity of 71% (cut off point= 16). The positive predictive value (PPV) is best for the detection of any mental disorder with a cut-off point of 16 (46%).

CONCLUSION

The HADS can be used as a screening instrument for the detection of comorbid depressive and anxiety disorders in patients with musculoskeletal disorders. Limitations in performance of screening instruments are due to: (1) different methodological approaches of tests (dimensional approach) and criterion (categorical approach); and (2) difficulties in diagnosing mental disorders in patients with prominent physical illness.

Psychiatric disorders and associated factors in cancer: results of an interview study with patients in inpatient, rehabilitation and outpatient treatment

An association between mental disorders, especially affective and anxiety disorders, and cancer has been reported in many studies. The present study investigated current (4-weeks-, 12-months-, and lifetime-prevalence rates of comorbid mental disorders in cancer patients. Through a cross-sectional design, 517 patients (75% female patients) from two acute inpatient care clinics, two rehabilitation clinics and nine specialised practices for oncology were examined with standardised scales for psychological burden and quality of life. Somatic parameters were assessed through standardised medical records. In the second-stage-examination, a sample of 200 patients was interviewed with standardised clinical interview (CIDI) in order to obtain DSM-IV diagnoses of mental disorders. Differences in the type of mental disorders were examined for gender, treatment setting, severity of cancer and physical impairment. Prevalence rates of mental disorders were 23.5% for the 4-weeks, 40% for the 12-months, and 56.5% for the lifetime periods. The current and 12-months rates of affective and anxiety disorders were approximately 25-33% higher than prevalence rates found in recent epidemiological studies of the general population. These higher rates were, however, mainly due to the preponderance of female patients with a higher risk for mental disorders compared with males. The most prevalent current disorders were affective (9.5%), and anxiety disorders (13%). Female gender was associated with an approximately 2-fold risk of mental disorders during the patient's lifespan. Current diagnosis of affective disorders in women was highly related to the cancer. Physical impairment was also associated with the frequency of current psychiatric disorders, especially affective and anxiety disorders. The frequency of mental disorders in cancer patients does not differ from results of recent international epidemiological studies of the normal population. The slightly higher rates of anxiety disorders are mainly due to phobias (simple, social and agoraphobia) without urgent need for treatment. A relatively large portion of patients, however, fulfil the criteria of minor depressive disorder which deserves clinical attention.

A new target for shigellosis: rational design and crystallographic studies of inhibitors of tRNA-guanine transglycosylase

Eubacterial tRNA-guanine transglycosylase (TGT) is involved in the hyper-modification of cognate tRNAs leading to the exchange of G34 at the wobble position in the anticodon loop by preQ1 (2-amino-5-(aminomethyl)pyrrolo[2,3-d]pyrimidin-4(3H)-one) as part of the biosynthesis of queuine (Q). Mutation of the tgt gene in Shigella flexneri results in a significant loss of pathogenicity of the bacterium, revealing TGT as a new target for the design of potent drugs against Shigellosis. The X-ray structure of Zymomonas mobilis TGT in complex with preQ1 was used to search for new putative inhibitors with the computer program LUDI. An initial screen of the Available Chemical Directory, a database compiled from commercially available compounds, suggested several hits. Of these, 4-aminophthalhydrazide (APH) showed an inhibition constant in the low micromolar range. The 1.95 A crystal structure of APH in complex with Z. mobilis TGT served as a starting point for further modification of this initial lead.

Chronically ill patients treated by spiritual healing improve in quality of life: results of a randomized waiting-list controlled study

OBJECTIVE

Little is known about the effects of distant healing in chronically ill patients, the population most likely to see a healer in practice. This study investigated whether distant healing as found in normal practice with patients representative of those seeking treatment from healers changes patients' quality of life substantially.

METHOD

Randomized, waiting-list controlled study of distant healing (anonymous, amulet, and allowing for personal contact) in chronically ill patients.

OUTCOME MEASURE

Patient-reported quality of life as expressed by the sum of all MOS SF-36 health survey items.

RESULTS

Sixty patients were treated by various methods of distant healing over 5 months; 59 patients were put on a waiting list (control). Quality of life improved significantly (p < 0.0005) in the treated group (10 points), while it remained stable in the control group. Positive expectation was significantly correlated with outcome.

CONCLUSION

Chronically ill patients who want to be treated by distant healing and know that they are treated improve in quality of life.

3alpha-Hydroxysteroid dehydrogenase/carbonyl reductase from Comamonas testosteroni: biological significance, three-dimensional structure and gene regulation

3alpha-Hydroxysteroid dehydrogenase/carbonyl reductase (3alpha-HSD/CR) catalyses the oxidoreduction at carbon 3 of steroid hormones and is postulated to initiate the complete mineralisation of the steroid nucleus to CO(2) and H(2)O in Comamonas testosteroni. The enzyme was found to be functional towards a variety of steroid substrates, including the steroid antibiotic fusidic acid. The enzyme also catalyses the carbonyl reduction of non-steroidal aldehydes and ketones such as a novel insecticide. It is suggested that 3alpha-HSD/CR contributes to important defense strategies of C. testosteroni against natural and synthetic toxicants. The 3alpha-HSD/CR gene (hsdA) is 774 base pairs long and the deduced amino acid sequence comprises 258 residues with a calculated molecular mass of 26.4 kDa. A homology search revealed 3alpha-HSD/CR as a new member of the short-chain dehydrogenase/reductase (SDR) superfamily. Upon gel permeation chromatography the purified enzyme elutes as a 49.4 kDa protein indicating a dimeric nature of 3alpha-HSD/CR. The protein was crystallised and the structure solved by X-ray analysis. The crystal structure reveals one homodimer per asymmetric unit, thereby verifying its dimeric nature. Dimerisation takes place via an interface essentially built-up by helix alphaG and strand betaG of each subunit. So far, this type of intermolecular contact has exclusively been observed in homotetrameric SDRs, but never in the structure of a homodimeric SDR. The formation of a tetramer is blocked in 3alpha-HSD/CR by the presence of a predominantly alpha-helical subdomain, which is missing in all other SDRs of known structure. The promoter domain was localised within the 93 bp region upstream of hsdA and the transcriptional start site was identified at 28 bp upstream of the translation start site. Interestingly, hsdA expression was found to be under negative control by two repressor proteins, the genes of which were found in opposite direction downstream or overlapping with hsdA. Based on our results, we propose that induction of hsdA expression in C. testosteroni by steroids actually appears to be a de-repression by preventing the binding of repressor proteins to regulatory regions.

The crystal structure of 3alpha -hydroxysteroid dehydrogenase/carbonyl reductase from Comamonas testosteroni shows a novel oligomerization pattern within the short chain dehydrogenase/reductase family

The crystal structure of 3alpha-hydroxysteroid dehydrogenase/carbonyl reductase from Comamonas testosteroni (3alpha-HSDH) as well as the structure of its binary complex with NAD(+) have been solved at 1.68-A and 1.95-A resolution, respectively. The enzyme is a member of the short chain dehydrogenase/reductase (SDR) family. Accordingly, the active center and the conformation of the bound nucleotide cofactor closely resemble those of other SDRs. The crystal structure reveals one homodimer per asymmetric unit representing the physiologically active unity. Dimerization takes place via an interface essentially built-up by helix alphaG and strand betaG of each subunit. So far this type of intermolecular contact has exclusively been observed in homotetrameric SDRs but never in the structure of a homodimeric SDR. The formation of a tetramer is blocked in 3alpha-HSDH by the presence of a predominantly alpha-helical subdomain which is missing in all other SDRs of known structure.

[Comorbid psychiatric disorders in cancer patients in acute inpatient treatment and medical rehabilitation]

An association between mental disorders, especially affective and anxiety disorders, and cancer has been reported in many clinical studies with inpatients. However, no data exist about the prevalence of mental disorders in patients undergoing acute care or rehabilitation treatment for cancer in Germany. The present study investigated 4-week, 6-month and lifetime prevalence rates of comorbid mental disorders in cancer. 256 patients from 2 rehabilitation clinics and 2 acute care hospitals were examined with standardized screening scales for psychological burden (GHQ-12, HADS) and quality of life (SF-36). Somatic parameters and interventions were assessed through standardized medical records from the attending oncologists. In the second-stage examination a subsample of 120 patients were interviewed with standardized clinical interview (CIDI) in order to obtain DSM-IV diagnoses of mental disorders. 44% (acute care) and 49% (rehabilitation) of the patients have high GHQ scores (cut-off > 4). Furthermore, more than 20% of the cancer patients have elevated scores on the HADS subscales depression and anxiety (cut-off > or = 11). Prevalence rates of mental disorders in the rehabilitation sample are 34% for the 4-week (vs. 24% in the acute care sample), 45% for the 6-month period (vs. 38%), and 79% for lifetime (vs. 49% in the acute care sample). The most frequent current disorders are affective (13% rehabilitation vs. 11% acute care) and anxiety disorders (17% in both samples). The rates of affective and anxiety disorders are much higher than the frequency of these disorders in recent epidemiological studies of the normal population in Germany. The high psychosocial burden expressed by the patients and the frequency of depressive and anxiety disorders emphasize the importance of (1) effective diagnostic strategies to recognize mental disorders, and (2) specialized psychosocial services in oncology, which provide psychological support and effective interventions for cancer patients in acute care and rehabilitation.

Screening orthologs as an important variable in crystallization: preliminary X-ray diffraction studies of the tRNA-modifying enzyme S-adenosyl-methionine:tRNA ribosyl transferase/isomerase

The genes encoding the tRNA-modifying enzyme S-adenosylmethionine:tRNA ribosyl transferase/isomerase (QueA) from 12 eubacterial sources were overexpressed in Escherichia coli and the resulting products were purified to homogeneity and subjected to crystallization trials. Using the hanging-drop vapour-diffusion method, crystals suitable for X-ray diffraction experiments were only obtained for the queA gene product from Bacillus subtilis. The crystals belong to the space group P422, with unit-cell parameters a = b = 100.7, c = 150.9 A. Using highly focused synchrotron radiation from the EMBL/ESRF beamline ID13 (Grenoble, France), diffraction to at least 3.2 A could be achieved. A selenomethionyl derivative of the protein was prepared and crystallized for future multiwavelength anomalous diffraction (MAD) experiments.

Crystal structure of the human U4/U6 small nuclear ribonucleoprotein particle-specific SnuCyp-20, a nuclear cyclophilin

The cyclophilin SnuCyp-20 is a specific component of the human U4/U6 small nuclear ribonucleoprotein particle involved in the nuclear splicing of pre-mRNA. It stably associates with the U4/U6-60kD and -90kD proteins, the human orthologues of the Saccharomyces cerevisiae Prp4 and Prp3 splicing factors. We have determined the crystal structure of SnuCyp-20 at 2.0-A resolution by molecular replacement. The structure of SnuCyp-20 closely resembles that of human cyclophilin A (hCypA). In particular, the catalytic centers of SnuCyp-20 and hCypA superimpose perfectly, which is reflected by the observed peptidyl-prolyl-cis/trans-isomerase activity of SnuCyp-20. The surface properties of both proteins, however, differ significantly. Apart from seven additional amino-terminal residues, the insertion of five amino acids in the loop alpha1-beta3 and of one amino acid in the loop alpha2-beta8 changes the conformations of both loops. The enlarged loop alpha1-beta3 is involved in the formation of a wide cleft with predominantly hydrophobic character. We propose that this enlarged loop is required for the interaction with the U4/U6-60kD protein.

Crystal structure of the surfactin synthetase-activating enzyme sfp: a prototype of the 4'-phosphopantetheinyl transferase superfamily

The Bacillus subtilis Sfp protein activates the peptidyl carrier protein (PCP) domains of surfactin synthetase by transferring the 4'-phosphopantetheinyl moiety of coenzyme A (CoA) to a serine residue conserved in all PCPs. Its wide PCP substrate spectrum renders Sfp a biotechnologically valuable enzyme for use in combinatorial non-ribosomal peptide synthesis. The structure of the Sfp-CoA complex determined at 1.8 A resolution reveals a novel alpha/beta-fold exhibiting an unexpected intramolecular 2-fold pseudosymmetry. This suggests a similar fold and dimerization mode for the homodimeric phosphopantetheinyl transferases such as acyl carrier protein synthase. The active site of Sfp accommodates a magnesium ion, which is complexed by the CoA pyrophosphate, the side chains of three acidic amino acids and one water molecule. CoA is bound in a fashion that differs in many aspects from all known CoA-protein complex structures. The structure reveals regions likely to be involved in the interaction with the PCP substrate.

Identification, characterization and crystal structure analysis of the human spliceosomal U5 snRNP-specific 15 kD protein

The U5 small ribonucleoprotein particle (snRNP) contains various proteins involved in catalytic activities mediating conformational rearrangements of the spliceosome. We have isolated and characterized the evolutionarily highly conserved human U5 snRNP-specific protein U5-15kD. The crystal structure of U5-15kD determined at 1.4 A resolution revealed a thioredoxin-like fold and represents the first structure of a U5 snRNP-specific protein known so far. With respect to human thioredoxin the U5-15kD protein contains 37 additional residues causing structural changes which most likely form putative binding sites for other spliceosomal proteins or RNA. Moreover, a novel intramolecular disulfide bond replaces the canonical one found in the thioredoxin family. Even though U5-15kD appears to lack protein disulfide isomerase activity, it is strictly required for pre-mRNA splicing in vivo as we demonstrate by genetic depletion of its ortholog in Saccharomyces cerevisiae. Our data suggest that the previously reported involvement of its Schizosaccharomyces pombe ortholog Dim1p in cell cycle regulation is a consequence of its essential role in pre-mRNA splicing.

Mutagenesis and crystallographic studies of Zymomonas mobilis tRNA-guanine transglycosylase to elucidate the role of serine 103 for enzymatic activity

The tRNA modifying enzyme tRNA-guanine transglycosylase (TGT) is involved in the exchange of guanine in the first position of the anticodon with preQ1 as part of the biosynthesis of the hypermodified base queuine (Q). Mutation of Ser90 to an alanine in Escherichia coli TGT leads to a dramatic reduction of enzymatic activity (Reuter, K. et al. (1994) Biochemistry 33, 7041-7046). To further clarify the role of this residue in the catalytic center, we have mutated the corresponding Ser103 of the crystallizable Zymomonas mobilis TGT into alanine. The crystal structure of a TGT(S103A)/preQ1 complex combined with biochemical data presented in this paper suggest that Ser103 is essential for substrate orientation in the TGT reaction.

Crystallization and preliminary crystallographic studies of Sfp: a phosphopantetheinyl transferase of modular peptide synthetases

The Bacillus subtilis Sfp protein is required for the non-ribosomal biosynthesis of the lipoheptapeptide antibiotic surfactin. It converts seven peptidyl carrier protein (PCP) domains of the surfactin synthetase SfrA-(A-C) to their active holo-forms by 4'-phosphopantetheinylation. The B. subtilis sfp gene was overexpressed in Escherichia coli and its gene product was purified to homogeneity and crystallized. Well diffracting single crystals were obtained from Sfp as well as from a selenomethionyl derivative, using sodium formate as a precipitant. The crystals belong to the tetragonal space group P41212/P43212, with unit-cell parameters a = b = 65.3, c = 150.5 A. They diffract beyond 2.8 A and contain one molecule in the asymmetric unit.

Overproduction, purification, crystallization and preliminary x-ray diffraction studies of the human spliceosomal protein U5-15kD

The gene coding for the human spliceosomal U5 snRNP-specific 15 kDa protein (U5-15kD) was overexpressed in Escherichia coli, its product purified to homogeneity and crystallized. Well diffracting single crystals were obtained by the vapour-diffusion method in hanging drops and subsequent macroseeding. The crystals belong to the orthorhombic space group P21212 with a = 62.3, b = 65.7, c = 37.1 A. They diffract to at least 3.0 A and contain one molecule in the asymmetric unit. A selenomethionine derivative of the protein was prepared and crystallized for multiwavelength anomalous diffraction (MAD) data collection.

Cloning and functional characterization of the genes encoding 3-dehydroquinate synthase (aroB) and tRNA-guanine transglycosylase (tgt) from Helicobacter pylori

The aroB gene from Helicobacter pylori strain P1 was cloned and further characterized by sequence analysis and by functional complementation of the aroB mutation in Escherichia coli. The aroB gene encodes the enzyme 3-dehydroquinate synthase which catalyzes one of the early steps in the shikimate pathway. This pathway, which creates aromatic molecules from sugar precursors, is present in prokaryotes, fungi and plants but is absent from mammalian cells. The predicted amino acid sequence of the H. pylori aroB gene product showed significant homology (30-40% identity and 50-60% similarity) to 3-dehydroquinate synthases from various other prokaryotes and eukaryotes. The single gene on a plasmid was biologically active in E. coli. It suppressed the specific phenotype of aroB mutants by restoring the shikimate pathway-dependent synthesis of aromatic amino acids and the production of the siderophore enterobactin. Two other reading frames were found adjacent to the aroB gene. The first, designated as orf1, had no significant homology to proteins and genes present in databases, whereas the second was found to share a significant degree of homology with the tgt gene encoding tRNA-guanine transglycosylase from a variety of other bacteria (40-50% identity and 60-70% similarity). The function of the tgt gene was confirmed by heterologous complementation. The gene on a plasmid was shown to complement the queuosine biosynthesis defect in a genetically defined tgt- strain of E. coli. The presence of the aroB gene and the putative tgt homologue in unrelated H. pylori strains was confirmed by Southern blot hybridization and by polymerase chain reaction with specific primers.

Mutagenesis and crystallographic studies of Zymomonas mobilis tRNA-guanine transglycosylase reveal aspartate 102 as the active site nucleophile

Procaryotic tRNA-guanine transglycosylase (TGT) catalyzes the posttranscriptional base exchange of the queuine precursor 7-aminomethyl-7-deazaguanine (preQ1) with the genetically encoded guanine at the wobble position of tRNAs specific for Asn, Asp, His, and Tyr. The X-ray structures of Zymomonas mobilis TGT and of its complex with preQ1 [Romier, C., Reuter, K., Suck, D., & Ficner, R. (1996) EMBO J. 15, 2850-2857] have revealed a specific preQ1 binding pocket and allowed a proposal for tRNA binding and recognition. We have used band-shift experiments in denaturing conditions to study the enzymatic reaction performed by TGT. The presence of shifted protein bands after incubation with tRNA followed by protein denaturation indicates a reaction mechanism involving a covalent intermediate. Inspection of the X-ray structures and comparison of the different procaryotic TGT sequences highlighted the conserved aspartate 102 as the most likely nucleophile. Mutation of this residue into alanine by site-directed mutagenesis leads to an inactive mutant unable to form a covalent intermediate with tRNA, proving that aspartate 102 is the active site nucleophile in TGT. To investigate the recognition of the wobble guanine in the preQ1 binding pocket, we mutated aspartate 156, the major recognition element for preQ1, into alanine and tyrosine. Both mutants are inactive in producing the final product, but the mutant D156A is able to form the covalent intermediate with tRNA in the first step of the reaction mechanism in comparable amounts to wild-type protein. Therefore, the binding of the wobble guanine in the preQ1 binding pocket is required for the cleavage of the glycosidic bond. The three mutants were crystallized and their X-ray structures determined. The mutants display only subtle changes to the wild-type protein, confirming that the observed biochemical results are due to the chemical substitutions rather than structural rearrangements.

Crystal structure of tRNA-guanine transglycosylase: RNA modification by base exchange

tRNA-guanine transglycosylases (TGT) are enzymes involved in the modification of the anticodon of tRNAs specific for Asn, Asp, His and Tyr, leading to the replacement of guanine-34 at the wobble position by the hypermodified base queuine. In prokaryotes TGT catalyzes the exchange of guanine-34 with the queuine (.)precursor 7-aminomethyl-7-deazaguanine (preQ1). The crystal structure of TGT from Zymomonas mobilis was solved by multiple isomorphous replacement and refined to a crystallographic R-factor of 19% at 1.85 angstrom resolution. The structure consists of an irregular (beta/alpha)8-barrel with a tightly attached C-terminal zinc-containing subdomain. The packing of the subdomain against the barrel is mediated by an alpha-helix, located close to the C-terminus, which displaces the eighth helix of the barrel. The structure of TGT in complex with preQ1 suggests a binding mode for tRNA where the phosphate backbone interacts with the zinc subdomain and the U33G34U35 sequence is recognized by the barrel. This model for tRNA binding is consistent with a base exchange mechanism involving a covalent tRNA-enzyme intermediate. This structure is the first example of a (beta/alpha)-barrel protein interacting specifically with a nucleic acid.