Membrane-bound structure and alignment of the antimicrobial beta-sheet peptide gramicidin S derived from angular and distance constraints by solid state 19F-NMR

The antimicrobial properties of the cyclic beta-sheet peptide gramicidin S are attributed to its destabilizing effect on lipid membranes. Here we present the membrane-bound structure and alignment of a derivative of this peptide, based on angular and distance constraints. Solid-state 19F-NMR was used to study a 19F-labelled gramicidin S analogue in dimyristoylphosphatidylcholine bilayers at a lipid:peptide ratio of 80:1 and above. Two equivalent leucine side chains were replaced by the non-natural amino acid 4F-phenylglycine, which serves as a highly sensitive reporter on the structure and dynamics of the peptide backbone. Using a modified CPMG multipulse sequence, the distance between the two 19F-labels was measured from their homonuclear dipolar coupling as 6 A. in good agreement with the known backbone structure of natural gramicidin S in solution. By analyzing the anisotropic chemical shift of the 19F-labels in macroscopically oriented membrane samples, we determined the alignment of the peptide in the bilayer and described its temperature-dependent mobility. In the gel phase, the 19F-labelled gramicidin S is aligned symmetrically with respect to the membrane normal, i.e., with its cyclic beta-sheet backbone lying flat in the plane of the bilayer, which is fully consistent with its amphiphilic character. Upon raising the temperature to the liquid crystalline state, a considerable narrowing of the 19F-NMR chemical shift dispersion is observed, which is attributed the onset of global rotation of the peptide and further wobbling motions. This study demonstrates the potential of the 19F nucleus to describe suitably labelled polypeptides in membranes, requiring only little material and short NMR acquisition times.

Prolonged pregnancy: surveillance of the fetus and the neonate and the course of labor and delivery

The perinatal events in 184 term control pregnancies and 129 prolonged pregnancies were prospectively compared. Fetal surveillance consisted of weekly biophysical profile testing. Thirty-two infants were dysmature, and 10 of these had advanced dysmaturity. The incidence of advanced dysmaturity rose quickly after 44 weeks. This group was at greater risk for fetal distress, lower Apgar scores, and emergency cesarean section. The combination of oligohydramnios, a suboptimal nonstress test, and a low profile score was highly predictive of a neonate with advanced dysmaturity. In the control pregnancies, the rate of induction of labor was 13.81% compared with 39.84% in the prolonged pregnancies. The induced labor group had a 51.32% cesarean section rate. Our approach to prolonged pregnancy consists of elective induction of labor when the cervix is favorable and biweekly profile testing when it is not; however, the high incidence of advanced dysmaturity after 44 weeks warrants delivery.

1H NMR spectroscopy of the binuclear Cu(II) active site of Streptomyces antibioticus tyrosinase

The 600 MHz 1H NMR spectrum of tyrosinase (31 kDa) of Streptomyces antibioticus in the oxidized, chloride-bound form is reported. The downfield part of the spectrum (15-55 ppm) exhibits a large number of paramagnetically shifted signals. The paramagnetism is ascribed to a thermally populated triplet state. The signals derive from six histidines binding to the metals through their Nepsilon atoms. There is no evidence for endogenous bridges. The exchange coupling, -2J, amounts to 298 cm(-1). In the absence of chloride the peaks broaden. This is ascribed to a slowing down of the electronic relaxation. The exchange coupling decreases to -2J=103 cm(-1).

Etiology of community-acquired pneumonia in a population-based study: link between etiology and patients characteristics, process-of-care, clinical evolution and outcomes

Background

The etiologic profile of community-acquired pneumonia (CAP) for each age group could be similar among inpatients and outpatients. This fact brings up the link between etiology of CAP and its clinical evolution and outcome. Furthermore, the majority of pneumonia etiologic studies are based on hospitalized patients, whereas there have been no recent population-based studies encompassing both inpatients and outpatients.

Methods

To evaluate the etiology of CAP, and the relationship among the different pathogens of CAP to patients characteristics, process-of-care, clinical evolution and outcomes, a prospective population-based study was conducted in Spain from April 1, 2006, to June 30, 2007. Patients (age >18) with CAP were identified through the family physicians and the hospital area.

Results

A total of 700 patients with etiologic evaluation were included: 276 hospitalized and 424 ambulatory patients. We were able to define the aetiology of pneumonia in 55.7% (390/700). The most frequently isolated organism was S. pneumoniae (170/390, 43.6%), followed by C. burnetti (72/390, 18.5%), M. pneumoniae (62/390, 15.9%), virus as a group (56/390, 14.4%), Chlamydia species (39/390, 106%), and L. pneumophila (17/390, 4.4%). The atypical pathogens and the S. pneumoniae are present in pneumonias of a wide spectrum of severity and age. Patients infected by conventional bacteria were elderly, had a greater hospitalization rate, and higher mortality within 30 days.

Conclusions

Our study provides information about the etiology of CAP in the general population. The microbiology of CAP remains stable: infections by conventional bacteria result in higher severity, and the S. pneumoniae remains the most important pathogen. However, atypical pathogens could also infect patients in a wide spectrum of severity and age.

In vitro susceptibility of Candida dubliniensis to current and new antifungal agents

BACKGROUND

Candida dubliniensis is a recently described Candida species closely related to Candida albicans, which has been associated with oral candidiasis in HIV-infected patients. Fluconazole-resistant strains of C. dubliniensis are easily obtained in vitro and this fact could be a complication if this resistance develops during treatment with this drug.

METHODS

In the present study, the in vitro antifungal susceptibilities of 36 C. dubliniensis clinical isolates and culture strains to current and new antifungal agents, such as amphotericin B (AMB), amphotericin B lipid complex (ABLC), amphotericin B colloidal dispersion (ABCD), 5-fluorocytosine (5FC), fluconazole (FLC), itraconazole (ITC), ketoconazole (KTC), liposomal amphoteri- cin B (LAMB), liposomal nystatin (LNYT), LY303366 (LY), SCH56592 (SCH), and voriconazole (VRC), were determined according to the National Committee for Clinical Laboratory Standards M27-A broth microdilution method for yeasts.

RESULTS

Most isolates of C. dubliniensis were susceptible to both new and current antifungal drugs, with 75.9% isolates susceptible to KTC, 86.2% to FLC and to ITC, and approximately 100% to the other antifungal agents tested. The cross-resistance phenotypes are detailed. Four isolates were resistant (MIC > or =64 microg/ml) to FLC. These 4 isolates were also resistant to KTC, and 3 of them were also resistant to ITC (MIC > or =1 microg/ml for both agents). However, these isolates were highly susceptible to 5FC and all polyene formulations (AMB, ABLC, ABCD, LAMB, and LNYT), triazole (SCH and VRC) and echinocandin (LY) antifungal agents.

CONCLUSION

The new liposomal and lipidic formulations of AMB, LNYT, and the new triazoles and echinocandins may provide new alternatives to FLC for the treatment of infections by C. dubliniensis.

Understanding the electronic properties of the CuA site from the soluble domain of cytochrome c oxidase through paramagnetic 1H NMR

The soluble domain of the subunit II of cytochrome c oxidase from Paracoccus versutus was cloned, expressed, and studied by 1H NMR at 600 MHz. The properties of the redox-active dinuclear CuA site in the paramagnetic mixed-valence Cu(I)-Cu(II) state were investigated in detail. A group of relatively sharp signals found between 30 and 15 ppm in the 1H NMR spectrum correspond to the imidazole protons of the coordinated histidines (H181 and H224). A second group of broader and farther shifted signals between 50 and 300 ppm are assigned to Hbeta protons of the bridging cysteines (C216 and C220); the protons from the weak M227 and E218 ligands do not shift outside of the diamagnetic envelope. About 40% of the total spin density appears delocalized over the cysteine-bridging ligands while a much smaller amount is delocalized on the two ligand histidines. The latter have similar spin density distributions. Analysis of the pattern of the hyperfine shifts of the Cys H beta protons shows that the ground state bears 2B3u character, in which the sulfur lobes in the singly occupied molecular orbital are aligned with the Cu-Cu axis. Analysis of the temperature dependence of the shifts of the Cys H beta signals leads to the conclusion that the 2B2u excited state is thermally accessible at room temperature (Delta E approximately kT).

Analysis of the paramagnetic copper(II) site of amicyanin by 1H NMR spectroscopy

Application of the tailored pulse sequences like super-WEFT allows the direct observation of the hyperfine-shifted signals of the paramagnetic Cu(II) forms of blue copper proteins in solution. The signals can be assigned by applying 2D NMR techniques, like EXSY, to solutions containing a mixture of reduced and oxidized species. The Fermi contact shift is separated from the pseudocontact shift on the basis of the known g-tensor anisotropy of the Cu(II) state, allowing the determination of a number of hyperfine-splitting constants between protons on the Cu ligands and the unpaired electron. These results are used to quantify the spin density distribution over the Cu ligands. In amicyanin about 50%-60% of the unpaired electron density is found on the ligands. It appears possible to quantify the Cu-S(Met) interaction on the basis of the NMR results. Application of the technique to the wild type forms of amicyanin and azurin and to two active site mutants of amicyanin (His96Asp and a plastocyanin-amicyanin loop exchange mutant) shows that the Cu-S(Met) interaction parallels the rhombicity and axial distortion of the Cu site.

Respiratory oscillations in yeast: clock-driven mitochondrial cycles of energization

Respiratory oscillations in continuous yeast cultures can be accounted for by cyclic energization of mitochondria, dictated by the demands of a temperature-compensated ultradian clock with a period of 50 min. Inner mitochondrial membranes show both ultrastructural modifications and electrochemical potential changes. Electron transport components (NADH and cytochromes c and c oxidase) show redox state changes as the organisms cycle between their energized and de-energized phases. These regular cycles are transiently perturbed by uncouplers of energy conservation, with amplitudes more affected than period; that the characteristic period is restored after only one prolonged cycle, indicates that mitochondrial energy generation is not part of the clock mechanism itself, but is responding to energetic requirement.

SEOM clinical guideline on unknown primary cancer (2017)

Cancer of unknown primary site is a histologically confirmed cancer that manifests in advanced stage, with no identifiable primary site following standard diagnostic procedures. Patients are initially categorized based on the findings of the initial biopsy: adenocarcinoma, squamous-cell carcinoma, neuroendocrine carcinoma, and poorly differentiated carcinoma. Appropriate patient management requires understanding several clinical and pathological features that aid in identifying several subsets of patients with more responsive tumors.

Determination of the magnetic axes of cobalt(II) and nickel(II) azurins from 1H NMR data: influence of the metal and axial ligands on the origin of magnetic anisotropy in blue copper proteins

The orientation and the axial, Deltachiax, and rhombic, Deltachirh, components of the magnetic susceptibility tensor anisotropy for the cobalt(II) and nickel(II) derivatives of azurin from Pseudomonas aeruginosa have been determined from 1H NMR data. For both derivatives, the axial geometry of the system determines the orientation of the chi-tensor, whose z-axis forms an angle of 18.6 and 20.1 degrees with the Cu-OGly45 axial bond in the cobalt(II) and nickel(II) derivatives, respectively. For protons close to this axis, large negative pseudocontact shifts are observed, while those close to the NNS plane of the equatorial ligands experience lower and positive pseudocontact shifts for the same distance. Dipolar shifts are larger in the cobalt derivative, not only because of the larger spin number but also due to its intrinsically higher anisotropy. The contact contribution to the hyperfine shifts for the coordinated residues has been evaluated and analyzed in terms of unpaired spin delocalization mechanisms and geometry considerations. The results are extended to other blue copper proteins whose cobalt derivatives have been studied by 1H NMR. The electronic structure and its implications in the redox properties of the native copper proteins are also commented.

The crystal structure of nickel(II)-azurin

The nickel(II)-azurin metalloderivative has been crystallized and its structure solved at 0.205-nm resolution by X-ray diffraction. The overall structure is not modified by the metal exchange and the only differences with regard to the native copper(II)-azurin occur in the metal site region. These variations affect principally the axial ligands. Nickel co-ordinates more strongly to the carbonyl oxygen of Gly45 while its distance to the Met121 S4 enlarges up to 0.330 nm. The resulting metal center structure is intermediate between those of the Cu(II) and Zn(II) azurins, and can be described as distorted tetrahedral. However, the existence of contact interaction between Met121 and the nickel ion is still possible as has been shown by paramagnetic 1H-NMR studies in solution.

1H-NMR study of a cobalt-substituted blue copper protein: Pseudomonas aeruginosa Co(II)-azurin

Substitution of copper by cobalt in blue copper proteins gives a paramagnetic metalloderivative suitable for paramagnetic NMR studies. A thorough analysis of the 1H-NMR spectrum of Pseudomonas aeruginosa Co(II)-azurin is presented here. All the observable contact-shifted signals as well as many other paramagnetic signals from protons placed up to about 1.0 nm around the metal center, including some residues belonging to functionally important parts of the protein like the hydrophobic patch and the His35 region, have been assigned. The results obtained permit the detection and study of structural variations like those originated by the His35 ionization, and allow us to draw a feasible picture of the metal coordination site. Contact-shifted signals correspond to the same five residues which are found in the coordination sphere of the native Cu(II)-azurin, i.e. His46, His117, Cys112, Met121 and Gly45. Among them, the histidine residues present a pattern of resonances typical for histidines coordinated to cobalt in other cobalt protein derivatives, and the cysteine signals clearly indicate a strong interaction with the paramagnetic Co(II) ion. In contrast, the Met121 signals indicate a weak but still existent contact interaction with the metal center. On the other hand, the very weak copper ligand, Gly45, appears here as clearly coordinated to cobalt. Results are consistent with a distorted tetrahedral metal site with the cobalt deviated from the N2S plane towards the Gly45 O axial position and weakly interacting with the Met121 sulfur.

Septic arthritis following arthroscopic meniscus repair: a cluster of three cases

Three cases of Staphylococcus epidermidis septic arthritis following inside-out arthroscopic meniscus repair within a 4-day period at the same facility are described. All three patients responded to surgical debridement and 4 to 6 weeks of intravenous antibiotics. In each instance, the meniscus and repair sutures were left intact; 12- to 38-month follow-up revealed no evidence of infection or meniscal symptoms. Epidemiological investigation implicated the meniscus repair cannulas as one of the few factors common to all three cases. Molecular typing of bacterial DNA revealed that two of the three isolated organisms showed identical pulsed-field gel electrophoretic patterns, implying a common source of inoculation. Experimental contamination of the cannulas revealed that only sterilization involving ultrasonification, lumen washing by water jet, and steam sterilization resulted in clean and sterile cannulas.

Paramagnetic cobalt and nickel derivatives of Alcaligenes denitrificans azurin and its M121Q mutant. A 1H NMR study

Using cobalt or nickel to replace copper in native azurin allows one to fingerprint the metal coordination site of the protein. The metal sites of wild type Alcaligenes denitrificans azurin and its M121Q mutant are clearly distinguishable through the paramagnetic 1H NMR spectra of the Ni(II) and Co(II) derivatives. In the wild type azurin, Gly45 coordinates to nickel or cobalt, while Met121 appears as a weak metal ligand. On the contrary, in the M121Q azurin mutant, the metal exhibits a clear preference for the Gln121, which coordinates through the side chain carbonyl oxygen, and Gly45 is not a ligand. Changes in the isotropic shifts and relaxation properties of signals from the Cys112, His46, and His117 metal ligands suggest a movement of the metal ion out of the equatorial plane, indicating that the metal site is tetrahedral. These effects are less pronounced in the Ni(II) M121Q azurin than in the Co(II) metalloderivative. The similarity between the NMR spectra of the Co(II) derivatives of stellacyanin and the M121Q azurin is in agreement with a very similar metal site in both proteins and supports the existence of a coordinated Gln in stellacyanin.

Paramagnetic NMR studies of blue and purple copper proteins

1H- and 13C-NMR spectroscopy is applied to investigate the CU(A) and type 1 active sites of copper proteins in solution. The analysis of hyperfine shifted 1H resonances allows the comparison of the electron spin density delocalization in the CU(A) site of the wild-type soluble domains of various cytochrome c oxidases (Thermus thermophilus, Paracoccus denitrificans, and Paracoccus versutus) and genetically engineered constructs (soluble domain of quinol oxidase from Escherichia coli and Thiobacillus versutus amicyanin). Comparable spin densities are found on the two terminal His ligands for the wild-type constructs as opposed to the engineered proteins where the spin is more unevenly distributed on the two His residues. A reevaluation of the Cys H(beta) chemical shifts that is in agreement with the data published for both the P. denitrificans and the P. versutus Cu(A) soluble domains confirms the thermal accessibility of the 2B(3u) electronic excited state and indicates the existence of slightly different spin densities on the two bridging Cys ligands. The 13C-NMR spectrum of isotopically enriched oxidized azurin from Pseudomonas aeruginosa reveals six fast relaxing signals, which can be partially identified by 1- and 2-dimensional (1-D, 2-D) direct detection techniques combined with 3-D triple resonance experiments. The observed contact shifts suggest the presence of direct spin density transfer and spin polarization mechanisms for the delocalization of the unpaired electron.

Paramagnetic NMR investigations of Co(II) and Ni(II) amicyanin

The paramagnetic 1H NMR spectra of the Co(II) and Ni(II) substituted forms of the type 1 blue copper protein (cupredoxin) amicyanin have been assigned. This is the first such analysis of a cupredoxin, which has a distorted tetrahedral active site with the ligands provided by two histidines, a cysteine and a methionine. The isotropic shifts of the resonances in these spectra are compared with those of Co(II) and Ni(II) azurin. A number of interesting similarities and differences are found. The coordination of the metal by the two equatorial histidine ligands is very similar in both proteins. The interaction between the introduced metal and the thiolate sulfur of the equatorial cysteine ligand is enhanced in the amicyanin derivatives. Resonances belonging to the weak axial methionine ligand exhibit much larger shifts in the amicyanin derivatives, indicative of shorter M(II)-S(Met) distances. The presence of shorter axial M(II)-S(Met) and equatorial M(II)-S(Cys) distances in both Co(II) and Ni(II) amicyanin is ascribed to the absence of a second axially interacting amino acid at the active site of this cupredoxin.

Amino acid substitutions enhancing thermostability of Bacillus polymyxa beta-glucosidase A

Mutations enhancing the thermostability of beta-glucosidase A of Bacillus polymyxa, a family 1 glycosyl hydrolase, have been obtained after hydroxylamine mutagenesis of a plasmid containing the bglA gene, transformation of Escherichia coli with the mutagenized plasmid, and identification of transformant colonies that showed beta-glucosidase activity after a thermal treatment that inactivated the wild-type enzyme. Two additive mutations have been characterized that cause replacement of glutamate at position 96 by lysine and of methionine at position 416 by isoleucine respectively. The thermoresistant mutant enzymes showed increased resistance to other denaturing agents, such as pH and urea, while their kinetic parameters did not change. CD spectra indicated that the E96K replacement caused an increase in alpha-helix content. The observed effect of the M416I mutation is consistent with the lower content of cysteine and methionine found in family 1 enzymes of thermophilic species compared with similar ones from mesophilic organisms.

The dynamic properties of the M121H azurin metal site as studied by NMR of the paramagnetic Cu(II) and Co(II) metalloderivatives

The M121H azurin mutant in solution presents various species in equilibrium that can be detected and studied by 1H NMR of the Cu(II) and Co(II) paramagnetic metalloderivatives. In both cases up to three species are observed in slow exchange, the proportions of which are different for the two metalloderivatives. Above pH 5 the major species displays a tetrahedral coordination in which the His121 can be observed as a coordinated residue. Its metal site corresponds to a new type of site that is defined as a type 1.5 site. The second and third species resemble the wild type (type 1) azurin and, above pH 4.5, they are present only at a low concentration. At low pH a protonation process increases the proportion of both type 1 species at the expense of the type 1.5 species. This process, characterized by a pKa = 4.3, is assigned to the protonation of His121. At high pH the NMR spectrum of the Co(II)-M121H azurin experiences an additional transition, which is not observed in the case of the Cu(II) protein. The dynamic properties of the M121H metal site appear to be related to changes in the coordination geometry and the strength of the axial interaction between the Ndelta1 (His121) and the metal.

Possible nosocomial transmission of psittacosis

OBJECTIVES

To investigate a cluster of seven pneumonia cases among persons exposed to a pet-shop worker hospitalized with psittacosis.

DESIGN

Epidemiological study of the outbreak, sero-diagnostic evaluation of exposed persons with pneumonia; and retrospective review of the pneumonia cases.

SETTING

450-bed teaching community hospital.

PARTICIPANTS

Employees of the nursing unit where the patient with psittacosis was hospitalized.

RESULTS

The index case had laboratory and clinical evidence of psittacosis. Four of the seven exposed persons who developed pneumonia had serologic results that met criteria for a diagnosis of psittacosis, and three met criteria for Chlamydia pneumoniae infection, possibly reflecting cross-reactivity between the microimmunofluorescence assays for the two diseases. The epidemiological graph suggested a relationship between the index case and the cluster of pneumonias in exposed individuals.

CONCLUSIONS

Psittacosis may have been transmitted person to person in a hospital setting.

Field preconcentration of cadmium from seawater by using a minicolumn packed with Amberlite XAD-4/4-(2-pyridylazo) resorcinol and its flow-injection-flame atomic absorption spectrometric determination at the ng L(-1) Level

A flow injection analysis-flame atomic absorption spectrometric method for the determination of cadmium in seawater was developed with the aim of yielding a sensitive assay with a low detection limit. The method employs a field flow preconcentration technique involving a minicolumn containing Amberlite XAD-4 impregnated with the complexing agent 4-(2-pyridylazo) resorcinol. A Plackett-Burman 2(7)x3/32 design for seven factors (sample pH, sample flow rate, eluent volume, eluent concentration, eluent flow rate, ethanol percentage in the eluent and minicolumn diameter) was carried out in order to find the significant variables affecting the field continuous preconcentration system (FCPS) and the flow injection elution manifold for cadmium determination in seawater samples by flame atomic absorption spectrometry. Cadmium can be preconcentrated with an enrichment factor of 1053 for a sample volume of 200 mL and a preconcentration time of 57 min. In these experimental conditions, the method provides a linear relationship between absorbance and cadmium concentration in the range from 22-1900 ng L(-1), with a detection limit (3SD) of 6 ng L(-1). The precision (expressed as relative standard deviation) for eleven independent determinations reached values of 8.9-0.8% in cadmium solutions of 50-700 ng L(-1). Analysis of certified reference materials (SLEW-3 and NASS-5) showed good agreement with the certified value. This procedure was applied to the determination of cadmium in seawater from Galicia (Spain).

Alpha-tocopherol interacts with natural micelle-forming single-chain phospholipids stabilizing the bilayer phase

The effect of the association of alpha-tocopherol (vitamin E) with single chain or very asymmetric phospholipids has been studied by 31P nuclear magnetic resonance, Fourier transform infrared spectroscopy, and light microscopy. Our results demonstrate that alpha-tocopherol stabilizes and forms bilayer structures in systems composed of either 1-palmitoyl-sn-glycero-3-phosphocholine, 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine, 1-O-hexadecyl-sn-glycero-3-phosphocholine, or 1,2-dipalmitoyl-sn-glycero-3- phosphocholine/1-palmitoyl-sn-glycero-3-phosphocholine, whereas in the absence of alpha-tocopherol all these systems produce micellar structures. The free hydroxyl group of alpha-tocopherol is shown to be important in stabilizing the bilayer structure by comparing the effects produced by an analog of alpha-tocopherol, alpha-tocopheryl acetate, which has the hydroxyl group blocked by an acetyl group. It is suggested that the complementary shapes of alpha-tocopherol and the asymmetric phospholipids may be the reason for the stabilization of the bilayer structure.

Replication of the Achievement Place model in California

Attempting to replicate procedures from Achievement Place, token reinforcement procedures were used to modify savings, conversational interruptions, and table-setting of delinquent boys residing in a home-style, community based, treatment setting. The tokens (points) were redeemable for various privileges and could be earned for specified appropriate behaviors and lost for specified inappropriate behaviors. Contingent point fines reduced the frequency of interruptions. Point rewards improved table-setting, but even large point rewards did not substantially increase savings. Baseline data indicated that lateness to dinner was not a problem, as it was in Achievement Place. Withdrawal of contingent points and back-up rewards did not disrupt the clean-up behavior of two boys.