Paramagnetic NMR Spectroscopy of Microperoxidase-8

Totally synthetic microperoxidase-11

A totally synthetic microperoxidase-11 (MP-11) is reported. Accordingly, the undecapeptide (VQKCAQCHTVE) was synthesized by solid-phase peptide synthesis followed by the thiol-ene click reaction with haemin for reconstitution. High-speed atomic force microscopy measurement conducted in water confirmed the protein reconstitution by visualizing the morphological differences as animated molecular images. The synthetic MP-11 showed a considerable magnitude of catalytic activity (27%) against the natural MP-11 in the oxidation of 3,3',5,5'-tetramethylbenzidine by hydrogen peroxide, whereas it showed very low (2.7%) activity of a synthetic variant with a point mutation (VQKCAQC M TVE, H8M). Slab waveguide spectroscopic measurements revealed that the ferrous/ferric redox reaction occurred by the direct electron transfer with specific spectral changes. Indeed, if hydrogen peroxide existed in the solution phase, the peroxidase-modified electrode showed catalytic current-voltage behaviour regardless of whether it was prepared using natural MP-11 or the synthetic MP-11. If a substrate recycling reaction was assumed, computer simulation well reproduced the experimental curves to give a global set of electrocatalytic reaction parameters. In any of the experiments, the synthetic MP-11 and natural MP-11 gave almost identical results. Our approach will be a convenient means of preparing MP-11, as well as its mutants, that does not rely on nature.

High Prevalence of Antibiotic Resistance in Isolates from the Middle Meatus of Children and Adults with Acute Rhinosinusitis

Background

The pathogens in acute rhinosinusitis are similar worldwide. An increase in antibiotic resistance has been shown in a large number of studies in recent years. The prevalence of resistance varies greatly in different countries. This study was performed to determine the endemic prevalence of antibiotic resistance in pathogens of acute rhinosinusitis in Taiwan.

Methods

Middle meatus discharge was taken for aerobic culture in 133 outpatients with the diagnosis of acute rhinosinusitis.

Results

One hundred two isolates of pathogens were found, including three major bacteria: Haemophilus influenzae (37.3%), Streptococcus pneumoniae (28.4%), and Moraxella catarrhalis (11.8%). Polymicrobial infections and positive cultures occurred more frequently in pediatric patients, as did recovery of M. catarrhalis infection. An extremely high percentage of resistance to first-line antibiotics was noted, viz., penicillin-nonsusceptible S. pneumoniae (PNSSP) (72.4%), ampicillin-resistant H. influenzae (60.5%), and M. catarrhalis (58.3%).

Conclusion

The high prevalence of drug resistance is a great threat to public health. Antibiotic use should be more prudent, especially in pediatric patients, who were found to be more susceptible to bacterial rhinosinusitis and multiple pathogenic infection.

Clinical practice guideline (update): adult sinusitis

OBJECTIVE

This update of a 2007 guideline from the American Academy of Otolaryngology--Head and Neck Surgery Foundation provides evidence-based recommendations to manage adult rhinosinusitis, defined as symptomatic inflammation of the paranasal sinuses and nasal cavity. Changes from the prior guideline include a consumer added to the update group, evidence from 42 new systematic reviews, enhanced information on patient education and counseling, a new algorithm to clarify action statement relationships, expanded opportunities for watchful waiting (without antibiotic therapy) as initial therapy of acute bacterial rhinosinusitis (ABRS), and 3 new recommendations for managing chronic rhinosinusitis (CRS).

PURPOSE

The purpose of this multidisciplinary guideline is to identify quality improvement opportunities in managing adult rhinosinusitis and to create explicit and actionable recommendations to implement these opportunities in clinical practice. Specifically, the goals are to improve diagnostic accuracy for adult rhinosinusitis, promote appropriate use of ancillary tests to confirm diagnosis and guide management, and promote judicious use of systemic and topical therapy, which includes radiography, nasal endoscopy, computed tomography, and testing for allergy and immune function. Emphasis was also placed on identifying multiple chronic conditions that would modify management of rhinosinusitis, including asthma, cystic fibrosis, immunocompromised state, and ciliary dyskinesia.

ACTION STATEMENTS

The update group made strong recommendations that clinicians (1) should distinguish presumed ABRS from acute rhinosinusitis (ARS) caused by viral upper respiratory infections and noninfectious conditions and (2) should confirm a clinical diagnosis of CRS with objective documentation of sinonasal inflammation, which may be accomplished using anterior rhinoscopy, nasal endoscopy, or computed tomography. The update group made recommendations that clinicians (1) should either offer watchful waiting (without antibiotics) or prescribe initial antibiotic therapy for adults with uncomplicated ABRS; (2) should prescribe amoxicillin with or without clavulanate as first-line therapy for 5 to 10 days (if a decision is made to treat ABRS with an antibiotic); (3) should reassess the patient to confirm ABRS, exclude other causes of illness, and detect complications if the patient worsens or fails to improve with the initial management option by 7 days after diagnosis or worsens during the initial management; (4) should distinguish CRS and recurrent ARS from isolated episodes of ABRS and other causes of sinonasal symptoms; (5) should assess the patient with CRS or recurrent ARS for multiple chronic conditions that would modify management, such as asthma, cystic fibrosis, immunocompromised state, and ciliary dyskinesia; (6) should confirm the presence or absence of nasal polyps in a patient with CRS; and (7) should recommend saline nasal irrigation, topical intranasal corticosteroids, or both for symptom relief of CRS. The update group stated as options that clinicians may (1) recommend analgesics, topical intranasal steroids, and/or nasal saline irrigation for symptomatic relief of viral rhinosinusitis; (2) recommend analgesics, topical intranasal steroids, and/or nasal saline irrigation) for symptomatic relief of ABRS; and (3) obtain testing for allergy and immune function in evaluating a patient with CRS or recurrent ARS. The update group made recommendations that clinicians (1) should not obtain radiographic imaging for patients who meet diagnostic criteria for ARS, unless a complication or alternative diagnosis is suspected, and (2) should not prescribe topical or systemic antifungal therapy for patients with CRS.

Artificial heme-proteins: determination of axial ligand orientations through paramagnetic NMR shifts

An empirical equation, describing the relationship between paramagnetic shifts and axial ligand orientations has been applied to an artificial bis-histidine ferriheme-protein, in order to determine the geometry of the active site.

Maxillary air density measurements for differentiating between acute and chronic rhinosinusitis

OBJECTIVE

Maxillary sinus air-fluid levels and sinus opacification may appear similar in cases of acute and chronic rhinosinusitis. Our aim was to evaluate whether air density analysis in addition to air-fluid level can be used as a metric to differentiate between cases of acute and chronic rhinosinusitis.

SUBJECTS AND METHODS

A prospective study of three patient groups (n = 73) who underwent sinus CT was performed. A study group composed of 23 patients with clinical acute rhinosinusitis was compared with two different control groups (one with chronic rhinosinusitis and the other with healthy sinuses) with 25 patients in each. In each case air density within the maxillary sinus was measured using a region of interest of 1 cm(2), 0.5 cm away from the sinus wall. The mean and SD of air density of each maxillary sinus were calculated from five sequential CT slices. We compared the results of each group using a paired Student t test and analysis of variance.

RESULTS

Mean air density was significantly higher in the acutely inflamed sinuses compared with chronic sinusitis and healthy aerated sinuses (-846.6 vs -980 and -975.8 HU, respectively; p < 0.05). Sinus air density SD was greater in the acutely inflamed sinus than in chronic sinusitis and healthy sinuses (78.3 vs 17.9 and 6.8 HU, respectively; p < 0.05).

CONCLUSION

Increased sinus air density and heterogeneity may help differentiate acute from chronic rhinosinusitis.

Redox state dependence of axial ligand dynamics in Nitrosomonas europaea cytochrome c552

Analysis of NMR spectra reveals that the heme axial Met ligand orientation and dynamics in Nitrosomonas europaea cytochrome c552 (Ne cyt c) are dependent on the heme redox state. In the oxidized state, the heme axial Met is fluxional, interconverting between two conformers related to each other by inversion through the Met δS atom. In the reduced state, there is no evidence of fluxionality, with the Met occupying one conformation similar to that seen in the homologous Pseudomonas aeruginosa cytochrome c551. Comparison of the observed and calculated pseudocontact shifts for oxidized Ne cyt c using the reduced protein structure as a reference structure reveals a redox-dependent change in the structure of the loop bearing the axial Met (loop 3). Analysis of nuclear Overhauser effects (NOEs) and existing structural data provides further support for the redox state dependence of the loop 3 structure. Implications for electron transfer function are discussed.

Inversion of the stereochemistry around the sulfur atom of the axial methionine side chain through alteration of amino acid side chain packing in Hydrogenobacter thermophilus cytochrome C552 and its functional consequences

In cytochrome c, the coordination of the axial Met Sδ atom to the heme Fe atom occurs in one of two distinctly different stereochemical manners, i.e., R and S configurations, depending upon which of the two lone pairs of the Sδ atom is involved in the bond; hence, the Fe-coordinated Sδ atom becomes a chiral center. In this study, we demonstrated that an alteration of amino acid side chain packing induced by the mutation of a single amino acid residue, i.e., the A73V mutation, in Hydrogenobacter thermophilus cytochrome c552 (HT) forces the inversion of the stereochemistry around the Sδ atom from the R configuration [Travaglini-Allocatelli, C., et al. (2005) J. Biol. Chem. 280, 25729-25734] to the S configuration. Functional comparison between the wild-type HT and the A73V mutant possessing the R and S configurations as to the stereochemistry around the Sδ atom, respectively, demonstrated that the redox potential (Em) of the mutant at pH 6.00 and 25 °C exhibited a positive shift of ∼20 mV relative to that of the wild-type HT, i.e., 245 mV, in an entropic manner. Because these two proteins have similar enthalpically stabilizing interactions, the difference in the entropic contribution to the Em value between them is likely to be due to the effect of the conformational alteration of the axial Met side chain associated with the inversion of the stereochemistry around the Sδ atom due to the effect of mutation on the internal mobility of the loop bearing the axial Met. Thus, the present study demonstrated that the internal mobility of the loop bearing the axial Met, relevant to entropic control of the redox function of the protein, is affected quite sensitively by the contextual stereochemical packing of amino acid side chains in the proximity of the axial Met.

Do symptoms and initial clinical probability predict the radiological diagnosis of acute sinusitis in children?

OBJECTIVE

To evaluate the value of signs and symptoms in children for the radiological diagnosis of acute sinusitis.

DESIGN

Prospective cohort study.

SETTING

University-affiliated tertiary care hospital.

PATIENTS

All children presenting with symptoms suggestive of acute sinusitis for whom sinus radiographs were ordered.

METHODS

Data were collected on the presence of specific symptoms and the initial probability of sinusitis. Criterion-based radiological diagnoses were made.

RESULTS

Three hundred ninety-two consecutive children were seen; 257 children had a radiological diagnosis of acute sinusitis (66%), 128 patients (33%) presented with complete opacity of at least one sinus and 14 (4%) children had an air-fluid level. Sensitivity, specificity, predictive values and likelihood ratios were measured for clinical findings. Classical symptoms (rhinorrhea lasting more than 10 days and purulent rhinorrhea) increased the likelihood ratios the most (1.3 and 1.34, respectively). Logistic regression showed two independent predictors: purulent rhinorrhea (odds ratio 2.0) and the presence of acute otitis media (odds ratio 2.6). The initial clinical probability was more accurate than any other single finding: high probability (likelihood ratio 2.0), intermediate probability (likelihood ratio 1.1) and low probability (likelihood ratio 0.6).

CONCLUSION

Classical symptoms are predictive of the presence of acute sinusitis as diagnosed on sinus radiographs. The physician's overall clinical impression, expressed as an initial probability, was superior to any single historical or examination finding in the diagnosis of acute sinusitis.

Canadian clinical practice guidelines for acute and chronic rhinosinusitis

This document provides healthcare practitioners with information regarding the management of acute rhinosinusitis (ARS) and chronic rhinosinusitis (CRS) to enable them to better meet the needs of this patient population. These guidelines describe controversies in the management of acute bacterial rhinosinusitis (ABRS) and include recommendations that take into account changes in the bacteriologic landscape. Recent guidelines in ABRS have been released by American and European groups as recently as 2007, but these are either limited in their coverage of the subject of CRS, do not follow an evidence-based strategy, or omit relevant stakeholders in guidelines development, and do not address the particulars of the Canadian healthcare environment.

Advances in understanding the pathophysiology of CRS, along with the development of appropriate therapeutic strategies, have improved outcomes for patients with CRS. CRS now affects large numbers of patients globally and primary care practitioners are confronted by this disease on a daily basis. Although initially considered a chronic bacterial infection, CRS is now recognized as having multiple distinct components (eg, infection, inflammation), which have led to changes in therapeutic approaches (eg, increased use of corticosteroids). The role of bacteria in the persistence of chronic infections, and the roles of surgical and medical management are evolving. Although evidence is limited, guidance for managing patients with CRS would help practitioners less experienced in this area offer rational care. It is no longer reasonable to manage CRS as a prolonged version of ARS, but rather, specific therapeutic strategies adapted to pathogenesis must be developed and diffused.

Guidelines must take into account all available evidence and incorporate these in an unbiased fashion into management recommendations based on the quality of evidence, therapeutic benefit, and risks incurred. This document is focused on readability rather than completeness, yet covers relevant information, offers summaries of areas where considerable evidence exists, and provides recommendations with an assessment of strength of the evidence base and degree of endorsement by the multidisciplinary expert group preparing the document.

These guidelines have been copublished in both Allergy, Asthma & Clinical Immunology and the Journal of Otolaryngology-Head and Neck Surgery.

Economic evaluation of Sinfrontal in the treatment of acute maxillary sinusitis in adults

Sinfrontal, a complex homeopathic medication, is popular in Germany for the treatment of ear, nose and throat and respiratory tract infections. Unlike many other homeopathic or herbal medications, the efficacy and safety of Sinfrontal has been demonstrated in a number of clinical studies of patients with sinusitis. To assess the cost effectiveness of Sinfrontal versus placebo in the treatment of adults with acute maxillary sinusitis (AMS) in Germany. A secondary objective was to assess the cost effectiveness of Sinfrontal versus standard treatment with antibacterials. Sinfrontal was compared with placebo in a cost-utility analysis based on data from a randomized controlled clinical trial over 3 weeks (Sinfrontal group: n = 57; placebo group: n = 56). Trial data were analysed from a societal perspective; resource use was valued with German unit costs for 2005. In a secondary analysis, the longer-term cost utility of Sinfrontal versus placebo was estimated over a total of 11 weeks based on an 8-week post-treatment observational phase. In addition, the cost effectiveness of Sinfrontal versus antibacterials was determined based on an indirect comparison of placebo-controlled trials. Sinfrontal led to incremental savings of euro 275 (95% CI 433, 103) per patient compared with placebo over 22 days, essentially due to the markedly reduced absenteeism from work (7.83 vs 12.9 workdays). Incremental utility amounted to 0.0087 QALYs (95% CI 0.0052, 0.0123), or 3.2 quality-adjusted life-days (QALDs). Bootstrapping showed that these findings were significant, with Sinfrontal being dominant in 99.9% of simulations. The results were robust to a number of sensitivity analyses. In the secondary analysis, Sinfrontal led to incremental cost savings of euro 511 and utility gains of 0.015 QALYs or 5.4 QALDs compared with placebo. Compared with antibacterials, Sinfrontal had a significantly higher cure rate (11% vs 59%; p < 0.001) at similar or lower costs. The results of this economic evaluation indicate that Sinfrontal may be a cost-effective treatment for AMS in adults.

The chemistry and biochemistry of heme c: functional bases for covalent attachment

A discussion of the literature concerning the synthesis, function, and activity of heme c-containing proteins is presented. Comparison of the properties of heme c, which is covalently bound to protein, is made to heme b, which is bound noncovalently. A question of interest is why nature uses biochemically expensive heme c in many proteins when its properties are expected to be similar to heme b. Considering the effects of covalent heme attachment on heme conformation and on the proximal histidine interaction with iron, it is proposed that heme attachment influences both heme reduction potential and ligand-iron interactions.

Clinical efficacy and time to symptom resolution of 5-day telithromycin versus 10-day amoxicillin-clavulanate in the treatment of acute bacterial sinusitis

OBJECTIVE

This study compared the clinical efficacy, time to symptom resolution, and tolerability of a 5-day regimen of telithromycin with a 10-day regimen of high-dose amoxicillin-clavulanate in acute bacterial sinusitis (ABS).

RESEARCH DESIGN AND METHODS

In this multinational (41 centers in Canada, Germany, Greece, Portugal, and Turkey), open-label, noninferiority study, patients >/=18 years old (n=298) with a clinical (>7 days' symptoms) and radiological (air/fluid level, total opacification, mucosal thickening >/=10 mm) diagnosis of ABS were randomized to receive telithromycin 800 mg once daily for 5 days or amoxicillin-clavulanate 875/125 mg twice daily for 10 days. Clinical efficacy and tolerability were assessed at the test-of-cure visit (days 17-21). Time to symptom resolution was based on patients' daily diary assessment of individual symptoms.

RESULTS

The per-protocol clinical success rate (primary endpoint) with telithromycin (88.6% (109/123)) was noninferior to that with amoxicillin-clavulanate (88.8% (111/125)) (95% confidence interval: -8.9 to 8.5). In the modified intention-to-treat (mITT) population, the median time for 50% reduction of total symptom scores was significantly shorter for telithromycin (4 days) vs. amoxicillin-clavulanate (5 days; p=0.044); median times for 75% reduction of total symptom scores were: telithromycin, 7 days; amoxicillin-clavulanate, 8 days (p=0.115). The median time for reduction of total symptom scores to the absent/very mild category (mITT population) was 6 days for telithromycin vs. 8 days for amoxicillin-clavulanate (p=0.04). All treatment-emergent adverse events (TEAEs) were mostly gastrointestinal and occurred in 20.7% (30/145) of telithromycin-treated patients vs. 31.8% (47/148) of amoxicillin-clavulanate-treated patients (p=0.034). One serious AE was reported in the telithromycin group, but it was considered not to be related to treatment.

CONCLUSIONS

This open-label, randomized study demonstrated that treatment of ABS with telithromycin resulted in comparable clinical efficacy, shorter times to symptom resolution, and fewer total TEAEs than treatment with amoxicillin-clavulanate.

Submolecular unfolding units of Pseudomonas aeruginosa cytochrome c-551

Hydrogen exchange rates for backbone amide protons of oxidized Pseudomonas aeruginosa cytochrome c-551 (P. aeruginosa cytochrome c) have been measured in the presence of low concentrations of the denaturant guanidine hydrochloride. Analysis of the data has allowed identification of submolecular unfolding units known as foldons. The highest-energy foldon bears similarity to the proposed folding intermediate for P. aeruginosa cytochrome c. Parallels are seen to the foldons of the structurally homologous horse cytochrome c, although the heme axial methionine-bearing loop has greater local stability in P. aeruginosa cytochrome c, in accord with previous folding studies. Regions of low local stability are observed to correspond with regions that interact with redox partners, providing a link between foldon properties and function.

Insights into porphyrin chemistry provided by the microperoxidases, the haempeptides derived from cytochrome c

The water-soluble haem-containing peptides obtained by proteolytic digestion of cytochrome c, the microperoxidases, have been used to explore aspects of the chemistry of iron porphyrins, and as mimics for some reactions catalysed by the haemoproteins, including the reactions catalysed by the peroxidases and the cytochromes P450. The preparation of the microperoxidases, their physical and chemical properties including their electronic structure, the kinetics and thermodynamics of their reactions with ligands, electrochemical studies and examples of their uses as haemoproteins mimics, is reviewed.

Redox infrared markers of the heme and axial ligands in microperoxidase: bases for the analysis of c-type cytochromes

Structural changes accompanying the change in the redox state of microperoxidase-8 (MP8), the heme-octapeptide obtained from cytochrome c, and its complexes with (methyl)imidazole ligands were studied by electrochemically induced Fourier transform IR (FTIR) difference spectroscopy. To correlate with confidence IR modes with a specific electronic state of the iron, we used UV-vis and electron paramagnetic resonance spectroscopy to define precisely the heme spin state in the samples at the millimolar concentration of MP8 required for FTIR difference spectroscopy. We identified four intense redox-sensitive IR heme markers, nu38 at 1,569 cm(-1) (ox)/1,554 cm(-1) (red), nu42 at 1,264 cm(-1) (ox)/1,242 cm(-1) (red), nu43 at 1,146 cm(-1) (ox), and nu44 at 1,124-1,128 cm(-1) (ox). The intensity of nu42 and nu43 was clearly enhanced for low-spin imidazole-MP8 complexes, while that of nu44 increased for high-spin MP8. These modes can thus be used as IR markers of the iron spin state in MP8 and related c-type cytochromes. Moreover, one redox-sensitive band at 1,044 cm(-1) (red) is attributed to an IR marker specific of c-type hemes, possibly the delta(CbH3)(2,4) heme mode. Other redox-sensitive IR bands were assigned to the MP8 peptide backbone and to the fifth and sixth axial heme ligands. The distinct IR frequencies for imidazole (1,075 cm(-1)) and histidine (1,105 cm(-1)) side chains in the imidazole-MP8 complex allowed us to provide the first direct determination of their pKa at pH 9 and 12, respectively.

Axial ligation and polypeptide matrix effects on the reduction potential of heme proteins probed on their cyanide adducts

The enthalpic and entropic changes accompanying the reduction reaction of the six-coordinate cyanide adducts of cytochrome c, microperoxidase-11 and a few plant peroxidases were measured electrochemically. Once the compensating changes in reduction enthalpy and entropy due to solvent reorganization effects are factorized out, it is found that cyanide binding stabilizes enthalpically the ferriheme following the order: cyochrome c > peroxidase > microperoxidase-11. The effect is inversely correlated to the solvent accessibility of the heme. Comparison of the reduction thermodynamics for the cyanide adducts of cytochrome c and plant peroxidases with those for microperoxidase-11 and myoglobin, respectively, yielded an estimate of the consequences of protein encapsulation and of the anionic character of the proximal histidine on the reduction potential of the heme-cyanide group. Insertion of the heme-CN group into the folded peptide chain of cyt c induces an enthalpy-based decrease in E degrees ' of approximately 100 mV, consistent with the lower net charge of the oxidized as compared to the reduced iron center, whereas a full imidazolate character of the proximal histidine stabilizes enthalpically the ferriheme by approximately 400 mV. The latter value should be best considered as an upper limit since it also includes some solvation effects arising from the nature of the protein systems being compared.

A new microperoxidase from Marinobacter hydrocarbonoclasticus

The preparation and characterization of a new microperoxidase obtained from proteinase K-treated cytochrome c(552) from Marinobacter hydrocarbonoclasticus (previously known as Pseudomonas nautica) are presented. This microperoxidase (MMP-5) has novel structural properties relative to previously reported microperoxidases, as the two intervening amino acid (X) residues within the consensual CXXCH c-type heme binding motif are missing, yielding a heme-pentapeptide with increased solubility in aqueous solvents and a 1-2 order of magnitude higher stability of the monomeric state relative to canonical microperoxidases. The electronic spectra in the near-UV and visible regions have been studied as a function of MMP-5 concentration and pH. The spectroscopic properties of MMP-5 are typical of microperoxidases with high-spin hexa- or pentacoordinate heme species dominant in the 1-8 pH range and low-spin states prevailing at higher pH values. In the presence of hydrogen peroxide, MMP-5 displays peroxidatic activities towards several compounds.

Training room management of medical conditions: infectious diseases

Management of infectious diseases in athletes encompasses a wide range of pathogens, clinical presentations, and treatment options. Certain athletic activities and training regimens may predispose athletes to increased risk of contracting infectious diseases, some of which may limit athletic participation and pose the threat of significant morbidity. The sports medicine physician plays an important role as a first line of defense in preventing, recognizing, and appropriately treating infectious diseases in athletes.

Conformational and Electronic Properties of a Microperoxidase in Aqueous Solution: A Computational Study

A theoretical study of the conformational properties of a small heme peptide in aqueous solution is carried out by classical, long-timescale molecular dynamics simulations. The electronic properties of this species, that is, the relative energies of its excited electronic states and the redox potential, are reproduced and related to the conformational behavior using the perturbed matrix method and basic statistical mechanics. Our results show an interesting coupling between the conformational transitions and the electronic properties. These investigations, beyond the biophysically relevant results addressing the long-standing question of the actual role of the enzyme structure on the enzyme activity, are also of some methodological interest since they offer a further computational perspective for including the electronic degrees of freedom into the modeling of rather complex molecular systems.

Characterization of a novel microperoxidase from Marinobacter hydrocarbonoclasticus by electrospray ionization tandem mass spectrometry

Microperoxidases are small heme-peptides obtained by proteolytic digestion of cytochrome c, exhibiting peroxidase activity. They consist of a short- or medium-length polypeptide chain, covalently linked to an iron protoporphyrin IX moiety via two thioether bonds involving Cys residues at the c-porphyrin A and B pyrrole rings. These small molecules are interesting for a wide range of possible applications. We have structurally characterized, by means of electrospray ionization (ESI) mass and tandem mass spectrometric experiments, a novel microperoxidase called MMP-5 (Marinobacter MicroPeroxidase-5), obtained by proteolytic digestion of cytochrome c552, a monoheminic electron-transfer protein isolated from Marinobacter hydrocarbonoclasticus. This microperoxidase, which still maintains the functional peptide moieties for peroxidase activity, is devoid of the two amino acids intercalating the Cys residues linked to the c-porphyrin, thus increasing its water solubility. Once submitted to the ESI source potential, MMP-5 showed an interesting tendency for the reduction of the iron protoporphyrin substructure. This behaviour was clearly evidenced by the mass shift exhibited by the reduced form.

Effects of axial methionine coordination on the in-plane asymmetry of the heme electronic structure of cytochrome c

The paramagnetic susceptibility ( chi) tensors of the oxidized forms of thermophile Hydrogenobacter thermophilus cytochrome c(552) (Ht cyt c(552)) and a quintuple mutant (F7A/V13 M/F34Y/E43Y/V78I; qm) of mesophile Pseudomonas aeruginosa cytochrome c(551) (Pa cyt c(551)) have been determined on the basis of the redox-dependent (1)H NMR shift changes of the main-chain NH and C(alpha)H proton resonances of non-coordinated amino acid residues and the NMR structures of the reduced forms of the corresponding proteins (J. Hasegawa, T. Yoshida, T. Yamazaki, Y. Sambongi, Y. Yu, Y. Igarashi, T. Kodama, K. Yamazaki, Y. Kyogoku, Y. Kobayashi (1998) Biochemistry 37:9641-9649; J. Hasegawa, S. Uchiyama, Y. Tanimoto, M. Mizutani, Y. Kobayashi, Y. Sambongi,Y. Igarashi (2000) J Biol Chem 275:37824-37828). From the chi tensors determined, we obtained the contact shifts for heme methyl proton resonances, which provided the heme electronic structures of the oxidized forms of Ht cyt c(552) and qm. We also characterized the heme electronic structure of the cyanide adducts of the proteins, where the axial Met was replaced by an exogenous cyanide ion, through the analysis of (1)H NMR spectra. The results indicated that the heme electronic structures of both the proteins in their oxidized forms with axial His and Met coordination are largely different to each other, while those in their cyanide adducts are similar to each other. These results demonstrated that the orientation of the axial Met sulfur lone pair, with respect to heme, predominantly contributes to the spin delocalization into the porphyrin-pi system of heme in the oxidized proteins with axial His and Met coordination.

Heme axial methionine fluxionality in Hydrogenobacter thermophilus cytochrome c552

The heme group in paramagnetic (S = 1/2) ferricytochromes c typically displays a markedly asymmetric distribution of unpaired electron spin density among the heme pyrrole beta substituents. This asymmetry is determined by the orientations of the heme axial ligands, histidine and methionine. One exception to this is ferricytochrome c(552) from Hydrogenobacter thermophilus, which has similar amounts of unpaired electron spin density at the beta substituents on all four heme pyrroles. Here, determination of the orientation of the magnetic axes and analysis of NMR line shapes for H. thermophilus ferricytochrome c(552) is performed. These data reveal that the unusual electronic structure for this protein is a result of fluxionality of the heme axial methionine. It is proposed that the ligand undergoes inversion at the pyramidal sulfur, and the rapid interconversion between two diastereomeric forms results in the unusual heme electronic structure. Thus a fluxional process for a metal-bound amino acid side chain has now been identified.

Preparation and reactivity studies of synthetic microperoxidases containing b-type heme

In order to create a heme environment that permits biomimicry of heme-containing peroxidases, a number of new hemin-peptide complexes--hemin-2(18)-glycyl-L-histidine methyl ester (HGH), hemin-2(18)-glycyl-glycyl-L-histidine methyl ester (HGGH), and hemin-2,18-bis(glycyl-glycyl-L-histidine methyl ester) (H2GGH)--have been prepared by condensation of glycyl-L-histidine methyl ester or glycyl-glycyl-L-histidine methyl ester with the propionic side chains of hemin. Characterization by means of UV/vis- and 1H NMR spectroscopy as well as cyclic- and differential pulse voltammetry indicates the formation of five-coordinate complexes in the case of HGH and HGGH, with histidine as an axial ligand. In the case of H2GGH, a six-coordinate complex with both imidazoles coordinated to the iron center appears to be formed. However, 1H NMR of H2GGH reveals the existence of an equilibrium between low-spin six-coordinate and high-spin five-coordinate species in solution. The catalytic activity of the hemin-peptide complexes towards several organic substrates, such as p-cresol, L-tyrosine methyl ester, and ABTS, has been investigated. It was found that not only the five-coordinate HGH and HGGH complexes, but also the six-coordinate H2GGH, catalyze the oxidation of substrates by H2O2. The longer and less strained peptide arm provides the HGGH complex with a slightly higher catalytic efficiency, as compared with HGH, due to formation of more stable intermediate complexes.

Imaging evaluation of sinusitis: diagnostic performance and impact on health outcome

Sinusitis is a highly prevalent disease, with a significant impact on the health care economy. Sinus CT is the primary imaging modality for evaluation of acute and chronic sinusitis. The roles of CT for patients with sinusitis are to assist clinical diagnosis, to evaluate the extent of disease, and to provide detailed anatomy necessary for treatment planning. Although sinus CT has been criticized for lack of specificity and correlation with patients' clinical symptoms, sinus CT may provide pivotal objective information that affects treatment decisions for acute and chronic sinusitis. This article provides a clinical overview and reviews the role of imaging studies in diagnosis and treatment of sinusitis.

Antibióticos en las infecciones respiratorias

El correcto tratamiento de las infecciones respiratorias representa un reto continuo para el médico de atención primaria. La mayor parte de las veces el tratamiento es empírico, debiendo combinar diferentes aspectos, como un diagnóstico correcto, microorganismos causales más probables, espectro de acción del antibiótico elegido, aumento de resistencias a antibióticos, aparición de nuevos fármacos, expectativas de adecuado cumplimiento y, por último, valorar la relación coste-efectividad. En este artículo se hace una revisión del tratamiento antibiótico de las infecciones respiratorias más frecuentes, como otitis, rinosinusitis, faringoamigdalitis, neumonía extrahospitalaria y reagudización de EPOC.

NMR investigation of ferricytochrome c unfolding: detection of an equilibrium unfolding intermediate and residual structure in the denatured state

Horse ferricytochrome c (cyt c) undergoes exchange of one of its axial heme ligands (Met-80) for one or more non-native ligands under denaturing conditions. We have used (1)H NMR spectroscopy to detect two conformations of paramagnetic cyt c with non-native heme ligation through a range of urea concentrations. One non-native form is an equilibrium unfolding intermediate observed under partially denaturing conditions and is attributed to replacement of Met-80 with one or more Lys side chains. The second non-native form, in which the native Met ligand is replaced by a His, is observed under strongly denaturing conditions. Thermodynamic analysis of these data indicates a relatively small DeltaG (17 kJ/mol) for the transition from native to the Lys-ligated intermediate and a significantly larger DeltaG (47 kJ/mol) for the transition from native to the His-ligated species. Although CD and fluorescence data indicate that the equilibrium unfolding of cyt c is a two-state process, these NMR results implicate an intermediate with His-Lys ligation.

Anaerobic chlorophyll isocyclic ring formation in Rhodobacter capsulatus requires a cobalamin cofactor

The isocyclic ring of bacteriochlorophyll (BChl) is formed by the conversion of Mg-protoporphyrin monomethyl ester (MPE) to protochlorophyllide (PChlide). Similarities revealed by blast searches with the putative anaerobic MPE-cyclase BchE suggested to us that this protein also uses a cobalamin cofactor. We found that vitamin B(12) (B(12))-requiring mutants of the bluE and bluB genes of Rhodobacter capsulatus, grown without B(12), accumulated Mg-porphyrins. Laser desorption/ionization time-of-flight (LDI-TOF) MS and NMR spectroscopy identified them as MPE and its 3-vinyl-8-ethyl (mvMPE) derivative. An in vivo assay was devised for the cyclase converting MPE to PChlide. Cyclase activity in the B(12)-dependent mutants required B(12) but not protein synthesis. The following reaction mechanism is proposed for this MPE-cyclase reaction. Adenosylcobalamin forms the adenosyl radical, which leads to withdrawal of a hydrogen atom and formation of the benzylic-type 13(1)-radical of MPE. Withdrawal of an electron gives the 13(1)-cation of MPE. Hydroxyl ion attack on the cation gives 13(1)-hydroxy-MPE. Withdrawal of three hydrogen atoms leads successively to 13(1)-keto-MPE, its 13(2)-radical, and cyclization to PChlide.

Histidine-tailed microperoxidase-10: a pH-dependent ligand switch

The electronic absorption and magnetic circular dichroism (MCD) spectra of ferric histidine-tailed microperoxidase-10 (His-MP10) change dramatically as the pH is raised from 1.8 to 11.8. Two distinct species are observed (pKa = 4.4). The spectra of acidic ferric His-MP10 nearly match those of ferric mesoporphyrin-reconstituted myoglobin and so the axial ligands are assigned to be histidine and water. The retention of histidine ligation below pH 4 contrasts to the behavior of myoglobin and horseradish peroxidase which convert to five-coordinate water ligated and then lose the heme prosthetic group at even lower pH. Neutral and alkaline ferric His-MP10 have spectra that are very similar to those of the imidazole complex of ferric mesoporphyrin-reconstituted myoglobin. Thus, we conclude that it is bis-histidine ligated with the C-terminal histidine bound as the sixth ligand. Thus, ferric His-MP10 exhibits a pH-dependent ligand switch with a change in axial ligation from water and histidine at low pH to bis-histidine at neutral and alkaline pH.

Paramagnetic NMR shifts in cyanoferricytochrome c. Investigation of thermal stability and deviations from Curie law behaviour

The paramagnetic shifts of 13C nuclei positioned alpha to the haem in cyanoferricytochrome c are reported and analysed in terms of molecular orbitals based on D4h symmetry with a rhombic perturbation. The temperature dependence of the Fermi contact and dipolar shifts of the haem and axial histidine ligand show deviations from Curie Law behaviour which are explained by a Boltzmann distribution between partially filled 3e(pi) molecular orbitals and the ground and first excited state Kramers doublets. The comprehensive explanation of the temperature dependence of the paramagnetic shifts leads to the conclusion that there is no detectable temperature dependence of the haem orientation or that of the His ligand orientation. This work also provides evidence for the role of the axial His ligand in determining the orientation of the magnetic z-axis.