A far-red-emitting ZnAl1.95Cr0.05O4 phosphor for plant growth LED applications

ZnAl_2-xCr_xO₄ (x = 0 and 0.05) samples were synthesized via a high-temperature solid-state reaction method. The structure, photoluminescence properties, EPR measurements, thermal stability, and chromaticity diagram of the far-red phosphor ZnAl_1.95Cr_0.05O₄ were investigated. These measurements have enabled us to study the Cr³⁺ transitions and the site symmetry of Cr³⁺ in the ZnAl₂O₄ host lattice and examine the suitability of ZnAl_1.95Cr_0.05O₄ for plant growth application. According to optical and EPR measurements, Cr³⁺ ions substitute Al³⁺ ions with D_3d symmetry in the ZnAl₂O₄ host. PLE measurement indicates that upon excitation at 390 nm and 530 nm, the far-red phosphor ZnAl_1.95Cr_0.05O₄ exhibited bright far-red emission around 687 nm. Photoluminescence phenomena show a sharp R line origin from the sublevels of the ²E_g(²G) → ⁴A₂(⁴F) transition in Cr³⁺ ions. The ²E_g level was split into ²E_g (Ē_g) and ²E_g (2Ā_g) levels in the distorted crystal field environment, and the sharp R line in the ZnAl₂O₄ matrix was split into R₁ and R₂ lines. In this paper, the temperature-dependent luminescence characteristics of ZnAl_1.95Cr_0.05O₄ have been investigated. As the temperature increased from 300 K to 440 K, a slight decrease in the intensity of the R1 and R2 lines was observed under excitation at 390 nm. The experimental results show that the ZnAl_1.95Cr_0.05O₄ phosphors exhibit a nearly zero-thermal-quenching behavior. The CIE chromaticity coordinates of the ZnAl_1.95Cr_0.05O₄ phosphor were located at the boundary of the chromaticity diagram, signifying that the phosphors possessed high color purity. The emissions of the ZnAl_1.95Cr_0.05O₄ phosphor match well with the PFR absorption of phytochromes in plants. The investigation indicates that ZnAl_1.95Cr_0.05O₄ is a potential far-red phosphor matching ultraviolet (UV) LED chips for plant growth applications.

Magnetostructural coupling in RFeO3 (R = Nd, Tb, Eu and Gd)

We investigate the interplay of magnetization and lattice vibrations in rare-earth orthoferrites RFeO₃, with a specific focus on non-symmetry-breaking anomalies. To do so, we study the magnetization, magnon excitations and lattice dynamics as a function of temperature in NdFeO₃, TbFeO₃, EuFeO₃ and GdFeO₃. The magnetization shows distinct temperature anomalous behavior for all investigated rare-earth orthoferrites, even in the compounds with no phase transitions occurring at those temperatures. Through spin-phonon coupling, these magnetic changes are mirrored by the FeO₆ rotation mode for all the studied RFeO₃, revealing a common magnetostructural effect associated with the octahedra rotations. The R³⁺ oscillation modes evidence a Fe³⁺/R³⁺ spins cross-talk for the NdFeO₃ and TbFeO₃ cases. Our work sheds light into the common magnetostructural coupling in rare-earth orthoferrites, and the important role of magnetic anisotropy and spin-orbit coupling strength of the R-Fe interactions on the spin-reorientation transition at high temperatures.

Laparoscopic pediatric pyeloplasty using the Flexdex® articulating needle driver: step-by-step video

Ureteropelvic junction (UPJ) stenosis is the most common cause of pathological neonatal hydronephrosis. UPJ obstruction may be treated conservatively in some cases, but surgery is indicated if symptoms occur or renal function deteriorates. Pyeloplasty is the procedure of choice for UPJ stenosis. Pyeloplasty can be performed by open laparoscopic or robotic technique. The laparoscopic technique is safe and may be associated with shorter length of hospital stay and reduced complications. Lately, robotic pyeloplasty has been performed with similar results, adding the benefits of easier suturing maneuverability, but with increased costs. Flexdex® is a laparoscopic articulating needle driver that improves maneuverability and ergonomics. In this video, a laparoscopic pyeloplasty with the Flexdex® needle drive is described. The case was treated without any intraoperative complications and with no significant blood loss, and the patient was discharged the day after the procedure. After 90 days of follow-up, there were no complications reported.

Profamille, programme de psychoéducation pour les familles d’un proche souffrant de schizophrénie : étude de l’impact du programme sur l’humeur des participants

Profamille est un programme psychoéducatif destiné aux aidants naturels des patients souffrant de schizophrénie. Il est standardisé, évalué et l’un des plus utilisés dans la francophonie. Il s’appuie sur des recherches sur les interactions entre le milieu familial et le cours de la maladie. L’une de ses particularités est de considérer l’action ciblée sur l’humeur des aidants comme l’un des paramètres essentiels de ses résultats positifs. En effet, l’amélioration de l’humeur doit permettre l’amélioration du coping des aidants, du climat émotionnel au sein de la famille et de l’acquisition des nouvelles connaissances délivrées par le programme. À notre connaissance, une seule étude antérieure sur l’évolution de l’humeur des participants à Profamille a été publiée, et elle concernait une version ancienne du programme. L’objectif de notre étude a donc été d’évaluer l’impact de Profamille sur l’humeur de 57 aidants inclus lors de 4 sessions ayant eu lieu au CHU de Caen, entre 2010 et 2014, grâce à un auto-questionnaire rempli en début et fin de programme (Center for Epidemiologic Studies-Depression scale [CES-D]). Nous avons distingué pour la comparaison statistique des scores d’évaluation (test de Wilcoxon bilatéral sur les données appariées) 3 groupes :

Les résultats ont montré que l’humeur s’améliorait tant dans le groupe à risque de syndrome dépressif (p < 0,001) que dans le groupe très probablement dépressif (p < 0,001). La comparaison des scores de l’humeur dans le groupe des sujets non déprimés n’était pas statistiquement significative. Ces résultats confirment l’impact positif de Profamille sur l’humeur des participants et son intérêt fondamental dans le travail avec les familles de nos patients souffrant de schizophrénie.

Do semantic categories activate distinct cortical regions? Evidence for a distributed neural semantic system

A key issue in cognitive neuroscience concerns the neural representation of conceptual knowledge. Currently, debate focuses around the issue of whether there are neural regions specialised for the processing of specific semantic attributes or categories, or whether concepts are represented in an undifferentiated neural system. Neuropsychological studies of patients with selective semantic deficits and previous neuroimaging studies do not unequivocally support either account. We carried out a PET study to determine whether there is any regional specialisation for the processing of concepts from different semantic categories using picture stimuli and a semantic categorisation task. We found robust activation of a large semantic network extending from left inferior frontal cortex into the inferior temporal lobe and including occipital cortex and the fusiform gyrus. The only category effect that we found was additional activation for animals in the right occipital cortex, which we interpret as being due to the extra visual processing demands required in order to differentiate one animal from another. We also carried out analyses in specific cortical regions that have been claimed to be preferentially activated for various categories, but found no evidence of any differential activation as a function of category. We interpret these data within the framework of cognitive accounts in which conceptual knowledge is represented within a nondifferentiated distributed system.

IL1 gene polymorphisms and unsuccessful dental implants

OBJECTIVES

This study aimed to analyse the association between polymorphisms in the IL1 gene cluster and failure of dental implants in a Portuguese population.

MATERIAL AND METHODS

A total of 155 Caucasian Portuguese subjects were divided into two groups: 100 with successful dental implants and 55 with unsuccessful dental implants. DNA was obtained through an oral mucosa scraping. PCR was used to identify the polymorphisms: single nucleotide changes in positions -889 of IL1A gene and +3953 of IL1B gene.

RESULTS

The prevalence of the polymorphisms -889IL1A gene and +3953IL1B gene, determined by the positive result of TGP (Genetic Test for Periodontitis; CGC, Genetics, Portugal), in the studied population rehabilitated with dental implants was of 33.50%. Allele 1 of the IL1B gene was the most prevalent (62.20%), followed by allele 1 of the IL1A gene (54.80%) and the least frequent was allele 2 of IL1B gene (37.40%). Success of dental implants was mainly associated with a negative TGP result, whereas no success was found to be related to a positive result. There were no statistically significant differences between the alleles 1 and 2 of the genes IL1A and IL1B and the tobacco and alcohol consumption for the success or no success of the dental implants.

CONCLUSIONS

The alleles 1 and 2 of IL1A gene and the alleles 1 and 2 of IL1B gene were statistically associated with the success or no success of the dental implants. Tobacco habit and alcohol consumption showed no statistically significant association with success or no success of the dental implants.

Metalloenzymes of the denitrification pathway

Denitrification, or dissimilative nitrate reduction, is an anaerobic process used by some bacteria for energy generation. This process is important in many aspects, but its environmental implications have been given particular relevance. Nitrate accumulation and release of nitrous oxide in the atmosphere due to excess use of fertilizers in agriculture are examples of two environmental problems where denitrification plays a central role. The reduction of nitrate to nitrogen gas is accomplished by four different types of metalloenzymes in four simple steps: nitrate is reduced to nitrite, then to nitric oxide, followed by the reduction to nitrous oxide and by a final reduction to dinitrogen. In this manuscript we present a concise updated review of the bioinorganic aspects of denitrification.

Differential expression of allergens on the internal and external surfaces of latex surgical gloves

BACKGROUND

Differences in latex allergen sensitization profiles have been described between children undergoing repeated surgical interventions and health care workers. The purpose of this study was to determine whether such sensitization profiles are associated with differences in the expression of latex allergen between the internal and external surfaces of surgical gloves.

METHODS

Extracts were obtained from whole surgical gloves as well as from their external and internal surfaces. The extracts were centrifuged, filtered, concentrated, dialyzed and lyophilized. The protein profile of the extracts was analyzed using hydrophobic interaction chromatography (HIC) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Immunoblotting was performed using sera from two patients with confirmed latex allergy. Latex recombinant allergen-specific IgE in these two patients was determined using a fluorescence enzyme immunoassay (FEIA) method. Latex allergen quantification was determined on both glove surfaces using an ELISA method.

RESULTS

HIC and SDS-PAGE showed qualitative and quantitative differences in proteins between the internal and external glove surfaces, with the former being much richer in proteins. Immunoblotting of glove extracts using sera from two latex-allergic health workers showed differences between glove surface extracts. ELISA quantification of latex allergens demonstrated that the internal glove surface had high amounts of Hev b 5 and Hev b 6.02 whereas the external surface showed Hev b 1, Hev b 3, and Hev b 6.02.

CONCLUSIONS

Our results reveal substantial differences in the composition of latex allergen profiles between the internal and external surfaces of surgical latex gloves, which may suggest a relationship between latex allergen localization and sensitization routes in different risk groups.

Effect of spermine and DNase on DNA release from bacteriophage T5

Bacterial viruses (bacteriophages) consist of nucleic acid protected by a protein envelope called capsid. At the start of infection, the phage genome is translocated into the bacterial cytoplasm. In vitro (and also in vivo), this DNA release can be triggered by binding a specific receptor protein to the phage tail. The force responsible for the release arises from energy stored in the capsid due to strong confinement of the DNA. We show that this force can be modified by adding molecules like spermine that affect DNA conformation. The tetravalent cation spermine can reduce the pressure inside the capsid and induce condensation of the released DNA. We examine the effect of spermine on DNA ejection from phage T5 by using light scattering and gel electrophoresis to measure the amount of DNA remaining in the capsid at the end of ejection. We discuss the results in terms of free energy minimization and we demonstrate that the presence of a DNA condensate outside the phage generates an additional force pulling passively on the DNA remaining inside the capsid.

Circadian and seasonal variation of endogenous ubiquinone plasma level

Coenzyme Q10 (CoQ10) or ubiquinone, a redox component of the mitochondrial electron transport chains, is a powerful antioxidant and membrane stabilizer that may prevent cellular damage during myocardial ischemia and reperfusion therapy. Coenzyme Q10 has been used primarily as an adjuvant therapy for some cardiomyopathies. However, one of the main problems in CoQ10 administration is the high variability of endogenous plasma and tissue levels, which seems to be dependent on several factors. This work explores temporal 24h and seasonal variation as well as gender and racial differences in endogenous plasma ubiquinone concentration. Coenzyme Q10 measurements (quantified by HPLC-UV) of 16 healthy volunteers were done during the daytime hours of activity beginning at 09:00h one day and ending at 09:00h the next day (13 different determinations) in two distinct months. April and October, of the year. A statistically significant circadian rhythm in plasma ubiquinone concentration that includes only the fundamental 24h component was demonstrated both in the April and October data. Furthermore, the time-point means of the ubiquinone concentration in the October study were invariably higher than those obtained in the April study. No statistically significant differences were found in CoQ10 concentration between male and female subjects, both in April and in October. In addition, racial differences were demonstrated; lower plasma ubiquinone levels were found in Caucasian compared to African subjects. However, the latter small group of subjects failed to demonstrate a circadian rhythm, neither in the April nor in the October analysis.

Respiratory mechanics and morphometric changes during anesthesia with ketamine in normal rats

Ketamine is believed to reduce airway and pulmonary tissue resistance. The aim of the present study was to determine the effects of ketamine on the resistive, elastic and viscoelastic/inhomogeneous mechanical properties of the respiratory system, lungs and chest wall, and to relate the mechanical data to findings from histological lung analysis in normal animals. Fifteen adult male Wistar rats were assigned randomly to two groups: control (N = 7) and ketamine (N = 8). All animals were sedated (diazepam, 5 mg, ip) and anesthetized with pentobarbital sodium (20 mg/kg, ip) or ketamine (30 mg/kg, ip). The rats were paralyzed and ventilated mechanically. Ketamine increased lung viscoelastic/inhomogeneous pressure (26%) compared to the control group. Dynamic and static elastances were similar in both groups, but the difference was greater in the ketamine than in the control group. Lung morphometry demonstrated dilation of alveolar ducts and increased areas of alveolar collapse in the ketamine group. In conclusion, ketamine did not act at the airway level but acted at the lung periphery increasing mechanical inhomogeneities possibly resulting from dilation of distal airways and alveolar collapse.

Structural organisation of the head-to-tail interface of a bacterial virus

In tailed icosahedral bacteriophages the connection between the 5-fold symmetric environment of the portal vertex in the capsid and the 6-fold symmetric phage tail is formed by a complex interface structure. The current study provides the detailed analysis of the assembly and structural organisation of such an interface within a phage having a long tail. The region of the interface assembled as part of the viral capsid (connector) was purified from DNA-filled capsids of the Bacillus subtilis bacteriophage SPP1. It is composed of oligomers of gp6, the SPP1 portal protein, of gp15, and of gp16. The SPP1 connector structure is formed by a mushroom-like portal protein whose cap faces the interior of the viral capsid in intact virions, an annular structure below the stem of the mushroom, and a second narrower annulus that is in direct contact with the helical tail extremity. The layered arrangement correlates to the stacking of gp6, gp15, and gp16 on top of the tail. The gp16 ring is exposed to the virion outside. During SPP1 morphogenesis, gp6 participates in the procapsid assembly reaction, an early step in the assembly pathway, while gp15 and gp16 bind to the capsid portal vertex after viral chromosome encapsidation. gp16 is processed during or after tail attachment to the connector region. The portal protein gp6 has 12-fold cyclical symmetry in the connector structure, whereas assembly-naïve gp6 exhibits 13-fold symmetry. We propose that it is the interaction of gp6 with other viral morphogenetic proteins that drives its assembly into the 12-mer state.

Evaluation of carboxymethylcellulose, hydroxypropylmethylcellulose, and aluminum hydroxide as potential carriers for rhBMP-2

Conventional iliac crest nonvascularized corticocancelous bone grafts and bone flaps have been used to treat bony defects. However, these treatments have some limitations, namely, the availability of donor tissue, donor site morbidity, difficulty to shape the bone flap to the defect, and complexity of the surgery. The bone morphogenetic protein (rhBMP-2) is osteoinductive. However, its implantation requires a matrix (carrier) in order to define the shape of the resulting bone and to retain the protein at the site for the time required for induction to occur. When the ideal carrier is found, an unlimited supply of material would be available for all applications where bone is needed. In this in vitro study, we evaluated the suitability of some potential carriers for rhBMP-2 by measuring the alkaline phosphatase (ALP) activity of fibroblast cultures. Either rhBMP-2 or sodium carboxymethylcellulose significantly increased the ALP activity, when used alone. When sodium carboxymethylcellulose was combined with rhBMP-2, there was an increase in the ALP activity, but lower than those obtained when the products were used alone. Hydroxypropylmethylcellulose alone did not affect ALP activity. However, the combination of rhBMP-2 with hydroxypropylmethylcellulose did not increase the ALP activity, despite the presence of rhBMP-2. Aluminium hydroxide proved to be an unsuitable rhBMP-2 adsorbent.

Substitution of murine ferrochelatase glutamate-287 with glutamine or alanine leads to porphyrin substrate-bound variants

Ferrochelatase (EC 4.99.1.1) is the terminal enzyme of the haem biosynthetic pathway and catalyses iron chelation into the protoporphyrin IX ring. Glutamate-287 (E287) of murine mature ferrochelatase is a conserved residue in all known sequences of ferrochelatase, is present at the active site of the enzyme, as inferred from the Bacillus subtilis ferrochelatase three-dimensional structure, and is critical for enzyme activity. Substitution of E287 with either glutamine (Q) or alanine (A) yielded variants with lower enzymic activity than that of the wild-type ferrochelatase and with different absorption spectra from the wild-type enzyme. In contrast to the wild-type enzyme, the absorption spectra of the variants indicate that these enzymes, as purified, contain protoporphyrin IX. Identification and quantification of the porphyrin bound to the E287-directed variants indicate that approx. 80% of the total porphyrin corresponds to protoporphyrin IX. Significantly, rapid stopped-flow experiments of the E287A and E287Q variants demonstrate that reaction with Zn(2+) results in the formation of bound Zn-protoporphyrin IX, indicating that the endogenously bound protoporphyrin IX can be used as a substrate. Taken together, these findings suggest that the structural strain imposed by ferrochelatase on the porphyrin substrate as a critical step in the enzyme catalytic mechanism is also accomplished by the E287A and E287Q variants, but without the release of the product. Thus E287 in murine ferrochelatase appears to be critical for the catalytic process by controlling the release of the product.

Differential effects of eprosartan and losartan at prejunctional angiotensin II receptors

A comparison was made of the influence of losartan and eprosartan on angiotensin II effects at pre- and postjunctional receptors of the canine pulmonary artery and at prejunctional receptors of the rat left ventricle. To study postjunctional contractile responses to angiotensin II, non-cumulative concentration-response curves were determined; to study prejunctional effects of angiotensin II, the tissues were preincubated with [3H]noradrenaline and then superfused and electrically stimulated (1 Hz, 2 ms, 50 mA, 5 min). Postjunctionally, both losartan and eprosartan caused a parallel shift of the concentration-response curve of angiotensin II to the right (pKd of 8.15 and 8.28, respectively). At the prejunctional level, while eprosartan, in concentrations similar to those which were effective postjunctionally (30-100 nM), antagonized the facilitatory effect on noradrenaline release in both the dog pulmonary artery and the rat ventricle, losartan was ineffective in concentrations up to 1 microM. It is concluded that pre-junctional receptors for angiotensin II in the canine pulmonary artery and in the rat left ventricle are different from postjunctional receptors of the canine pulmonary artery. It is proposed that the prejunctional receptors of these tissues are atypical AT1 or "AT1B-like" receptors.

Mössbauer characterization of the iron-sulfur clusters in Desulfovibrio vulgaris hydrogenase

The periplasmic hydrogenase of Desulfovibrio vulgaris (Hildenbourough) is an all Fe-containing hydrogenase. It contains two ferredoxin type [4Fe-4S] clusters, termed the F clusters, and a catalytic H cluster. Recent X-ray crystallographic studies on two Fe hydrogenases revealed that the H cluster is composed of two sub-clusters, a [4Fe-4S] cluster ([4Fe-4S](H)) and a binuclear Fe cluster ([2Fe](H)), bridged by a cysteine sulfur. The aerobically purified D. vulgaris hydrogenase is stable in air. It is inactive and requires reductive activation. Upon reduction, the enzyme becomes sensitive to O(2), indicating that the reductive activation process is irreversible. Previous EPR investigations showed that upon reoxidation (under argon) the H cluster exhibits a rhombic EPR signal that is not seen in the as-purified enzyme, suggesting a conformational change in association with the reductive activation. For the purpose of gaining more information on the electronic properties of this unique H cluster and to understand further the reductive activation process, variable-temperature and variable-field Mössbauer spectroscopy has been used to characterize the Fe-S clusters in D. vulgaris hydrogenase poised at different redox states generated during a reductive titration, and in the CO-reacted enzyme. The data were successfully decomposed into spectral components corresponding to the F and H clusters, and characteristic parameters describing the electronic and magnetic properties of the F and H clusters were obtained. Consistent with the X-ray crystallographic results, the spectra of the H cluster can be understood as originating from an exchange coupled [4Fe-4S]-[2Fe] system. In particular, detailed analysis of the data reveals that the reductive activation begins with reduction of the [4Fe-4S](H) cluster from the 2+ to the 1+ state, followed by transfer of the reducing equivalent from the [4Fe-4S](H) subcluster to the binuclear [2Fe](H) subcluster. The results also reveal that binding of exogenous CO to the H cluster affects significantly the exchange coupling between the [4Fe-4S](H) and the [2Fe](H) subclusters. Implication of such a CO binding effect is discussed.

Mössbauer characterization of the iron-sulfur clusters in Desulfovibrio vulgaris hydrogenase

The periplasmic hydrogenase of Desulfovibrio vulgaris (Hildenbourough) is an all Fe-containing hydrogenase. It contains two ferredoxin type [4Fe-4S] clusters, termed the F clusters, and a catalytic H cluster. Recent X-ray crystallographic studies on two Fe hydrogenases revealed that the H cluster is composed of two sub-clusters, a [4Fe-4S] cluster ([4Fe-4S](H)) and a binuclear Fe cluster ([2Fe](H)), bridged by a cysteine sulfur. The aerobically purified D. vulgaris hydrogenase is stable in air. It is inactive and requires reductive activation. Upon reduction, the enzyme becomes sensitive to O(2), indicating that the reductive activation process is irreversible. Previous EPR investigations showed that upon reoxidation (under argon) the H cluster exhibits a rhombic EPR signal that is not seen in the as-purified enzyme, suggesting a conformational change in association with the reductive activation. For the purpose of gaining more information on the electronic properties of this unique H cluster and to understand further the reductive activation process, variable-temperature and variable-field Mössbauer spectroscopy has been used to characterize the Fe-S clusters in D. vulgaris hydrogenase poised at different redox states generated during a reductive titration, and in the CO-reacted enzyme. The data were successfully decomposed into spectral components corresponding to the F and H clusters, and characteristic parameters describing the electronic and magnetic properties of the F and H clusters were obtained. Consistent with the X-ray crystallographic results, the spectra of the H cluster can be understood as originating from an exchange coupled [4Fe-4S]-[2Fe] system. In particular, detailed analysis of the data reveals that the reductive activation begins with reduction of the [4Fe-4S](H) cluster from the 2+ to the 1+ state, followed by transfer of the reducing equivalent from the [4Fe-4S](H) subcluster to the binuclear [2Fe](H) subcluster. The results also reveal that binding of exogenous CO to the H cluster affects significantly the exchange coupling between the [4Fe-4S](H) and the [2Fe](H) subclusters. Implication of such a CO binding effect is discussed.

Redox potential measurements of the Mycobacterium tuberculosis heme protein KatG and the isoniazid-resistant enzyme KatG(S315T): insights into isoniazid activation

Mycobacterium tuberculosis KatG is a multifunctional heme enzyme responsible for activation of the antibiotic isoniazid. A KatG(S315T) point mutation is found in >50% of isoniazid-resistant clinical isolates. Since isoniazid activation is thought to involve an oxidation reaction, the redox potential of KatG was determined using cyclic voltammetry, square wave voltammetry, and spectroelectrochemical titrations. Isoniazid activation may proceed via a cytochrome P450-like mechanism. Therefore, the possibility that substrate binding by KatG leads to an increase in the heme redox potential and the possibility that KatG(S315T) confers isoniazid resistance by altering the redox potential were examined. Effects of the heme spin state on the reduction potentials of KatG and KatG(S315T) were also determined. Assessment of the Fe(3+)/Fe(2+) couple gave a midpoint potential of ca. -50 mV for both KatG and KatG(S315T). In contrast to cytochrome P450s, addition of substrate had no significant effect on either the KatG or KatG(S315T) redox potential. Conversion of the heme to a low-spin configuration resulted in a -150 to -200 mV shift of the KatG and KatG(S315T) redox potentials. These results suggest that isoniazid resistance conferred by KatG(S315T) is not mediated through changes in the heme redox potential. The redox potentials of isoniazid were also determined using cyclic and square wave voltammetry, and the results provide evidence that the ferric KatG and KatG(S315T) midpoint potentials are too low to promote isoniazid oxidation without formation of a high-valent enzyme intermediate such as compounds I and II or oxyferrous KatG.

Role of calcium in gentamicin-induced mesangial cell activation

Gentamicin-induced decreases in glomerular filtration rate have been associated to a marked decline in the glomerular capillary ultrafiltration coefficient which could be due to an active contraction of mesangial cells. In the present work we assessed a possible role of cytosolic Ca2+ as a mediator that leads to contraction and proliferation induced by gentamicin on mesangial cells. Gentamicin (10(-5)M) induced an increase in cytosolic free Ca2+, that was fully inhibited by the calcium channel blocker, verapamil, and by the endoplasmic reticulum calcium release blocker, TMB8. Gentamicin induced a planar surface area reduction in cultured mesangial cells, that was blunted by verapamil and TMB-8. Gentamicin also stimulated [3H]thymidine incorporation into DNA and increased viable cell number, effects that were reduced by both, verapamil and TMB-8. Gentamicin stimulated the expression of the AP1 protein; this expression was partially blunted by verapamil and TMB-8. Moreover, verapamil inhibited gentamicin-induced PAF synthesis from mesangial cells. In summary, gentamicin directly raised intracellular Ca2+ activating both calcium influx from external medium and calcium release from internal stores. This increase is responsible of cellular activation (contraction and proliferation) and PAF synthesis induced by gentamicin on mesangial cells.

Platelet activation is increased in cyclosporin A-induced hypertensive rats

One of the most severe side effects of the immunosuppressive agent, cyclosporin A (CsA), is increased risk of thromboembolic complications and drug-related hypertension. Because platelets might be involved in these processes, we tested the possibility of CsA affecting platelet activation, which might contribute to these adverse drug reactions. The experiments were done using Wistar rats, treated or not (control) with CsA (Sandimmun Neoral), 5 and 30 mg/kg/day, for 7 weeks. Systolic, diastolic, and mean blood pressures, intracellular free calcium concentration ([Ca2+]i), platelet serotonin (5-HT) contents, and aggregation were determined, at weeks 0, 2, and 7 of treatment. Inositol phosphates (InsP) production, platelet thromboxane A2 (TXA2) generation, and morphology of platelets, through electron microscopy studies, also were compared. It was demonstrated that blood pressures increased in the CsA-treated groups, when compared with the control group, after 2 and 7 weeks of administration. CsA at both "attack" and "maintenance" doses increased basal, 5-HT, and thrombin-evoked [Ca2+]i after 2 and 7 weeks versus the control group. However, basal and evoked InsP production was stimulated by 5 mg/kg of CsA, but inhibited by 30 mg/kg, when compared with the control. Platelet 5-HT contents decreased significantly after 2 and 7 weeks in the CsA-treated groups, when compared with the control group. Collagen-induced whole blood platelet aggregation increased drastically in the "attack" CsA-treated group, whereas adenosine diphosphate (ADP)-induced platelet aggregation did not reach statistical significance. Finally, in vitro basal, collagen-, and ADP-evoked platelet TXA2 generation increased in both CsA concentrations, versus the control. In conclusion, our study demonstrates that both CsA doses alter platelet calcium homeostasis (even affecting the calcium fluxes differently), 5-HT and TXA2 contents and aggregation, which might contribute to the development and/or maintenance of high blood pressures and increased risk of thromboembolic complications.

Cell polarization and adhesion in a motile pathogenic protozoan: role and fate of the Entamoeba histolytica Gal/GalNAc lectin

The human pathogenic protozoan Entamoeba histolytica is a motile cell polarized into a front pseudopod and a rear uroid. The amoebic Gal/GalNAc surface lectin is a major adhesion molecule composed of an immunodominant 170-kDa heavy subunit, mostly extracellular except for a short cytoplasmic tail, and of an extracellular light subunit. The binding of multivalent ligands triggers lectin capping and recruitment to the uroid. The properties of the Gal/GalNAc lectin and its role in amoeba adhesion and uroid polarization are reviewed in the context of the molecular mechanisms underlying cell polarization and locomotion.

Improved bioavailability of a micronized megestrol acetate tablet formulation in humans

Megestrol acetate, a progestogen widely used in the palliative treatment of endometrial carcinoma and breast cancer, is currently administered orally as a solid dosage form. Bioavailability of the drug following oral administration is closely related to the effectiveness and safety profile of the drug in formulation. Improved immediate-release formulations should allow improved drug delivery into the systemic circulation and, at the end, to the site of action. The micronization of drugs is one of the technological procedures to achieve such a purpose. This paper reports the design and results obtained in an in vivo study of the bioavailability of a micronized megestrol acetate tablet formulation compared to a conventional form. A significant increase in the drug bioavailability was observed, in either the rate or the extent of absorption. In vitro dissolution data of the two study formulations reflected the in vivo findings.

Purification, characterization, and preliminary crystallographic study of copper-containing nitrous oxide reductase from Pseudomonas nautica 617

The aerobic purification of Pseudomonas nautica 617 nitrous oxide reductase yielded two forms of the enzyme exhibiting different chromatographic behaviors. The protein contains six copper atoms per monomer, arranged in two centers named Cu(A) and Cu(Z). Cu(Z) could be neither oxidized nor further reduced under our experimental conditions, and exhibits a 4-line EPR spectrum (g(x)=2.015, A(x)=1.5 mT, g(y)=2.071, A(y)=2 mT, g(z)=2.138, A(z)=7 mT) and a strong absorption at approximately 640 nm. Cu(A) can be stabilized in a reduced EPR-silent state and in an oxidized state with a typical 7-line EPR spectrum (g(x)=g(y)= 2.021, A(x) = A(y)=0 mT, g(z) = 2.178, A(z)= 4 mT) and absorption bands at 480, 540, and approximately 800 nm. The difference between the two purified forms of nitrous oxide reductase is interpreted as a difference in the oxidation state of the Cu(A) center. In form A, Cu(A) is predominantly oxidized (S = (1)/(2), Cu(1.5+)-Cu(1.5+)), while in form B it is mostly in the one-electron reduced state (S = 0, Cu(1+)-Cu(1+)). In both forms, Cu(Z) remains reduced (S = 1/2). Complete crystallographic data at 2.4 A indicate that Cu(A) is a binuclear site (similar to the site found in cytochrome c oxidase) and Cu(Z) is a novel tetracopper cluster [Brown, K., et al. (2000) Nat. Struct. Biol. (in press)]. The complete amino acid sequence of the enzyme was determined and comparisons made with sequences of other nitrous oxide reductases, emphasizing the coordination of the centers. A 10.3 kDa peptide copurified with both forms of nitrous oxide reductase shows strong homology with proteins of the heat-shock GroES chaperonin family.

In vitro packaging of DNA of the Bacillus subtilis bacteriophage SPP1

In vitro packaging of bacteriophage SPP1 DNA into procapsids is described and the requirements of this process were determined. Combination of proheads with an extract supplying terminase, DNA and phage tails yielded up to 10(7 )viable phages per milliliter of in vitro reaction under optimized conditions. The presence of neutral polymers and polyamines had a concentration and type dependent effect in the packaging reaction. The terminase donor extract lost rapidly activity at 30 degrees C in contrast to the stability of the prohead donor extract. Maturation to infective virions was observed using both procapsids assembled in SPP1 infected cells and procapsid-like structures assembled in Escherichia coli that overexpressed the SPP1 prohead gene clusters. Neither a majority of aberrant capsid-related structures present in the latter material nor procapsids lacking the portal protein inhibited DNA packaging. Addition of purified portal protein reduced DNA packaging activity in vitro only at concentrations 20-fold higher than those found in the SPP1 infected cell. The SPP1 DNA packaged in vitro originated exclusively from the terminase donor extract. This packaging selectivity was not observed in vivo during mixed infections. The data are compatible with a model for processive headful DNA packaging in which terminase and DNA co-produced in the same cell are tightly associated and can effectively discriminate the portal vertex of DNA packaging-proficient proheads from aberrant structures, from portal-less procapsids, and from isolated portal protein.

Shape and DNA packaging activity of bacteriophage SPP1 procapsid: protein components and interactions during assembly

The procapsid of the Bacillus subtilis bacteriophage SPP1 is formed by the major capsid protein gp13, the scaffolding protein gp11, the portal protein gp6, and the accessory protein gp7. The protein stoichiometry suggests a T=7 symmetry for the SPP1 procapsid. Overexpression of SPP1 procapsid proteins in Escherichia coli leads to formation of biologically active procapsids, procapsid-like, and aberrant structures. Co-production of gp11, gp13 and gp6 is essential for assembly of procapsids competent for DNA packaging in vitro. Presence of gp7 in the procapsid increases the yield of viable phages assembled during the reaction in vitro five- to tenfold. Formation of closed procapsid-like structures requires uniquely the presence of the major head protein and the scaffolding protein. The two proteins interact only when co-produced but not when mixed in vitro after separate synthesis. Gp11 controls the polymerization of gp13 into normal (T=7) and small sized (T=4?) procapsids. Predominant formation of T=7 procapsids requires presence of the portal protein. This implies that the portal protein has to be integrated at an initial stage of the capsid assembly process. Its presence, however, does not have a detectable effect on the rate of procapsid assembly during SPP1 infection. A stable interaction between gp6 and the two major procapsid proteins was only detected when the three proteins are co-produced. Efficient incorporation of a single portal protein in the procapsid appears to require a structural context created by gp11 and gp13 early during assembly, rather than strong interactions with any of those proteins. Gp7, which binds directly to gp6 both in vivo and in vitro, is not necessary for incorporation of the portal protein in the procapsid structure.

The distribution of catecholamines between plasma and platelets in cyclosporin A-induced hypertensive rats

One of the most serious side effects of the immunosuppressive agent, cyclosporin A (CsA), is drug-related hypertension. As it is generally accepted, the sympathetic nervous system may play an important role in the development or maintenance of this abnormal pathophysiological situation. This study is aimed at assessing plasma and platelet catecholamines, and a possible connection to cyclosporin A-induced increased arterial blood pressure. It was thus based on an investigation in which Wistar rats were divided into three groups: one taking only orange juice (control) and the other two receiving 5 and 30 mg kg(-1)('trough' and 'peak') of cyclosporin A (Sandimmun Neoral), daily, for 7 weeks. Plasma and platelet noradrenaline, adrenaline and dopamine levels and arterial blood pressures were evaluated before the start of the study (week 0) and after 2, 4 and 7 weeks. Plasma and platelet catecholamines increased drastically in the 'peak' CsA concentration-treated group, which contrasts with the slight decrease observed in the group treated with the 'trough' concentration. However, both groups revealed an increase in blood pressures, when compared with the control group. These findings suggest that at least 'peak' cyclosporin A concentration alters significantly the plasma and platelets catecholamines levels, which may contribute to the cyclosporin A-induced hypertension. Other contributions, regardless of catecholamine content disturbances, might occur, at least at 'trough' CsA concentrations.

Purification and characterization of a tungsten-containing formate dehydrogenase from Desulfovibrio gigas

An air-stable formate dehydrogenase (FDH), an enzyme that catalyzes the oxidation of formate to carbon dioxide, was purified from the sulfate reducing organism Desulfovibrio gigas (D. gigas) NCIB 9332. D. gigas FDH is a heterodimeric protein [alpha (92 kDa) and beta (29 kDa) subunits] and contains 7 +/- 1 Fe/protein and 0.9 +/- 0.1 W/protein. Selenium was not detected. The UV/visible absorption spectrum of D. gigas FDH is typical of an iron-sulfur protein. Analysis of pterin nucleotides yielded a content of 1.3 +/- 0.1 guanine monophosphate/mol of enzyme, which suggests a tungsten coordination with two molybdopterin guanine dinucleotide cofactors. Both Mössbauer spectroscopy performed on D. gigas FDH grown in a medium enriched with (57)Fe and EPR studies performed in the native and fully reduced state of the protein confirmed the presence of two [4Fe-4S] clusters. Variable-temperature EPR studies showed the presence of two signals compatible with an atom in a d(1) configuration albeit with an unusual relaxation behavior as compared to the one generally observed for W(V) ions.

The peripheral serotonergic system and platelet aggregation in cyclosporin A-induced hypertensive rats

Cyclosporin A plays an important role in preventing rejection in allograft transplant recipients. However, the therapeutic use of cyclosporin A is associated with increased incidence of thromboembolic complications and drug-related hypertension. In order to study the mechanisms by which cyclosporin A induces these abnormal pathophysiological situations, we have assessed the platelet serotonin contents and whole blood platelet aggregation in control rats as well as in rats treated (orally) with 30 and 5 mg/kg/day of cyclosporin A, after 2 and 7 weeks of treatment. These doses correspond respectively to CsA "peak" and "trough" concentrations achieved in human blood in clinical practice (immediately following an intake of a daily dose of CsA and when the blood concentration stabilizes, respectively). Both trough and peak doses caused an increase in blood pressure after 2 and 7 weeks. Platelet serotonin content decreased in the cyclosporin-treated groups, in contrast with the control. Collagen-induced whole blood platelet aggregation increased drastically for the peak concentration-treated group, while adenosine 5'-diphosphate-induced platelet aggregation did not reach statistical significance. Finally, in vitro platelet thromboxane A2 generation increased in cyclosporin A concentrations when platelets were stimulated with either collagen or adenosine 5'-diphosphate. In conclusion, both tested cyclosporin A concentrations induced important changes in platelet serotonin and thromboxane content and aggregation, factors which may play a decisive role in the development and/or maintenance of hypertension and thrombotic complications.

Effect of the ionic environment on the molecular structure of bacteriophage SPP1 portal protein

Bacteriophage SPP1 portal protein is a large cyclical homo-oligomer composed of 13 subunits. The solution structure and assembly behavior of this protein with high-point rotational symmetry was characterized. The purified protein was present as a monodisperse population of 13-mers, named gp6H, at univalent salt concentrations in the hundred millimolar range (>/= 250 mM NaCl) or in the presence of bivalent cations in the millimolar range (>/= 5 mM MgCl2). Gp6H had a slightly higher sedimentation coefficient, a smaller shape-dependent frictional ratio, and a higher rate of intersubunit cross-linking in the presence of magnesium than in its absence. In the absence of bivalent cations and at univalent salt concentrations below 250 mM, the 13-mer molecules dissociated partially into stable monomers, named gp6L. The monomer had a somewhat different shape from the subunit present in the 13-mer, but maintained a defined tertiary structure. The association-dissociation equilibrium was mainly between the monomer and the 13-mer with a minor population of intermediate oligomers. Their interconversion was strongly influenced by the ionic environment. Under physiological conditions, the concentration of Mg2+ found in the Bacillus subtilis cytoplasm (10-50 mM) probably promotes complete association of gp6 into 13-mer rings with a compact conformation.

Structure of the 13-fold symmetric portal protein of bacteriophage SPP1

We have determined the three-dimensional structure of bacteriophage SPP1 portal protein (gp6) using electron microscopy at liquid-helium temperatures and angular reconstitution. The 13-fold symmetric gp6 oligomer is a turbine-shaped structure with three distinct regions: a conical stem with a central channel; the turbine wings region; and a fringe of small 'tentacles' at the end of the channel exposed to the viral head interior. The tentacle region appears flexible and may be associated with a particular function - sensing when the correct amount of DNA has been packaged. The three-dimensional structure of the gp6 SizA mutant, which packages a smaller chromosome, reveals significant differences in that region.

Mode of action of AraR, the key regulator of L-arabinose metabolism in Bacillus subtilis

The AraR protein is a negative regulator involved in L-arabinose-inducible expression of the Bacillus subtilis araABDLMNPQ-abfA metabolic operon and of the araE/araR genes that are organized as a divergent transcriptional unit. The two ara gene clusters are found at different positions in the bacterial chromosome. AraR was overproduced in Escherichia coli and purified to more than 95% homogeneity. AraR binds specifically to DNA fragments carrying the promoter region of the ara genes. DNase I protection assays showed that AraR binds to two sequences within the promoters of the araABDLMNPQ-abfA operon and the araE gene, and to one sequence in the araR promoter. The AraR target sequences are palindromic and share high identity, defining a 16 bp AraR consensus operator sequence showing half-symmetry, ATTTGTAC. Binding of AraR to DNA was inhibited by L-arabinose but not by other sugars. The two operator sites within the araABDLMNPQ-abfA operon and araE promoters are located on the same side of the DNA helix, and a pattern of enhanced and diminished DNase I cleavage was observed between them, but not in the araR promoter. Quantitative DNase I footprinting in DNA templates containing one, two or three AraR binding sites showed that the repressor binds cooperatively to the two operator sites within the metabolic operon and araE promoters but not to the site located in the araR promoter. These results are consistent with two modes for AraR transcriptional repression that might correlate with different physiological requirements: a high level of repression is achieved by DNA bending requiring two in-phase operator sequences (metabolic operon and araE transport gene), whereas binding to a single operator, which autoregulates araR expression, is 10-fold less effective.

Biochemical and spectroscopic characterization of overexpressed fuscoredoxin from Escherichia coli

Fuscoredoxin is a unique iron containing protein of yet unknown function originally discovered in the sulfate reducers of the genus Desulfovibrio. It contains two iron-sulfur clusters: a cubane [4Fe-4S] and a mixed oxo- and sulfido-bridged 4Fe cluster of unprecedented structure. The recent determination of the genomic sequence of Escherichia coli (E. coli) has revealed a homologue of fuscoredoxin in this facultative microbe. The presence of this gene in E. coli raises interesting questions regarding the function of fuscoredoxin and whether this gene represents a structural homologue of the better-characterized Desulfovibrio proteins. In order to explore the latter, an overexpression system for the E. coli fuscoredoxin gene was devised. The gene was cloned from genomic DNA by use of the polymerase chain reaction into the expression vector pT7-7 and overexpressed in E. coli BL21(DE3) cells. After two chromatographic steps a good yield of recombinant protein was obtained (approximately 4 mg of pure protein per liter of culture). The purified protein exhibits an optical spectrum characteristic of the homologue from D. desulfuricans, indicating that cofactor assembly was accomplished. Iron analysis indicated that the protein contains circa 8 iron atoms/molecule which were shown by EPR and Mössbauer spectroscopies to be present as two multinuclear clusters, albeit with slightly altered spectroscopic features. A comparison of the primary sequences of fuscoredoxins is presented and differences on cluster coordination modes are discussed on the light of the spectroscopic data.

Excision of pulmonary metastases of osteogenic sarcoma of the limbs

OBJECTIVE

The combination of surgery and chemotherapy improves the prognosis of patients with osteogenic sarcoma of the limbs without detectable metastases at presentation. However, lung metastases are a frequent complication. To evaluate the role of the resection of pulmonary metastases of osteogenic sarcoma of the limbs, we have reviewed our experience with this type of surgery, combined with a multidrug chemotherapy protocol.

PATIENTS AND METHODS

From January 89 to December 97, 198 patients operated on for osteogenic sarcomas of the limbs were followed in our centre. Of these, 31 patients (15.7%), with a mean age of 25 years (range 10-54 years), developed lung metastases and had undergone 45 thoracotomies. All patients received chemotherapy, followed by resection of metastatic lesions and additional chemotherapy. The mean time interval between resection of the primary tumour and the diagnosis of lung metastases was 22 months (4-122 months). Eight patients (25.8%) needed more than one (2-4) thoracotomy. The mean time interval between the first and second thoracic surgeries was 9.2 months (2-14 months).

RESULTS

There was no operative mortality or major morbidity. During the 45 thoracotomies, five lobectomies and 40 wedge resections were necessary. The mean number of metastases resected per thoracotomy was 3.4 (range 1-10). The degree of necrosis was evaluated by seriated sections for a histologic study. In the end the mean necrotic volume was calculated. A strong correlation was found between the degree of necrosis of the metastases and the need for reoperation for new metastatic lesions, because all the patients who needed more than one operation had less than 80% of necrosis of metastases. The patients were followed for a mean period of 28 months (6-72 months). Ten patients (32.2%) died of related causes at a mean of 19.4 months after thoracic surgery, three of whom had more than one operation. The 3-year survival after metastasectomy was 61%. Patients without pulmonary metastases had a 3-year survival of 79%.

CONCLUSIONS

In patients with lung metastases of an osteogenic sarcoma, the combination of chemotherapy and surgery improves the outcome. In our series the mortality was not influenced by the number or thoracotomies required.

Reactions of nitric oxide with the reduced non-heme diiron center of the soluble methane monooxygenase hydroxylase

The soluble methane monooxygenase system from Methylococcus capsulatus (Bath) catalyzes the oxidation of methane to methanol and water utilizing dioxygen at a non-heme, carboxylate-bridged diiron center housed in the hydroxylase (H) component. To probe the nature of the reductive activation of dioxygen in this system, reactions of an analogous molecule, nitric oxide, with the diiron(II) form of the enzyme (Hred) were investigated by both continuous and discontinuous kinetics methodologies using optical, EPR, and Mössbauer spectroscopy. Reaction of NO with Hred affords a dinitrosyl species, designated Hdinitrosyl, with optical spectra (lambdamax = 450 and 620 nm) and Mössbauer parameters (delta = 0.72 mm/s, DeltaEQ = 1.55 mm/s) similar to those of synthetic dinitrosyl analogues and of the dinitrosyl adduct of the reduced ribonucleotide reductase R2 (RNR-R2) protein. The Hdinitrosyl species models features of the Hperoxo intermediate formed in the analogous dioxygen reaction. In the presence of protein B, Hdinitrosyl builds up with approximately the same rate constant as Hperoxo ( approximately 26 s-1) at 4 degrees C. In the absence of protein B, the kinetics of Hdinitrosyl formation were best fit with a biphasic A --> B --> C model, indicating the presence of an intermediate species between Hred and Hdinitrosyl. This result contrasts with the reaction of Hred with dioxygen, in which the Hperoxo intermediate forms in measurable quantities only in the presence of protein B. These findings suggest that protein B may alter the positioning but not the availability of coordination sites on iron for exogenous ligand binding and reactivity.

Inspiratory flow-volume curve in snoring patients with and without obstructive sleep apnea

We analyzed the flow-volume curves of 50 patients with complaints of snoring and daytime sleepiness in treatment at the Pneumology Unit of the University Hospital of Brasília. The total group was divided into snorers without obstructive sleep apnea (OSA) (N = 19) and snorers with OSA (N = 31); the patients with OSA were subdivided into two groups according to the apnea/hypopnea index (AHI): AHI < 20/h (N = 14) and AHI > 20/h (N = 17). The control group (N = 10) consisted of nonsmoking subjects without complaints of snoring, daytime sleepiness or pulmonary diseases. The population studied (control and patients) consisted of males of similar age, height and body mass index (BMI); spirometric data were also similar in the four groups. There was no significative difference in the ratio of forced expiratory and inspiratory flows (FEF50%/FIF50%) in any group: control. 0.89; snorers, 1.11; snorers with OSA (AHI < 20/h), 1.42, and snorers with OSA (AHI > 20/h), 1.64. The FIF at 50% of vital capacity (FIF50%) of snoring patients with or without OSA was lower than the FIF50% of the control group (P < 0.05): snorers 4.30 l/s; snorers with OSA (AHI < 20/h) 3.69 l/s; snorers with OSA (AHI > 20/h) 3.17 l/s and control group 5.48 l/s. The FIF50% of patients with severe OSA (AHI > 20/h) was lower than the FIF50% of snorers without OSA (P < 0.05): 3.17 l/s and 4.30 l/s, respectively. We conclude that 1) the FEF50%/FIF50% ratio is not useful for predicting OSA, and 2) FIF50% is decreased in snoring patients with and without OSA, suggesting that these patients have increased upper airway resistance (UAR).

Bioequivalence evaluation of two omeprazole enteric-coated formulations in humans

Omeprazole, a proton pump inhibitor, effectively suppresses the gastric acid secretion in the parietal cells of the stomach. Several previously published papers focus on the pharmacokinetics of the drug and its interactions with physiological aspects or with other drugs. The increasing number of omeprazole containing products available in the market, raises questions of therapeutic equivalence and/or generic substitution. The bioequivalence evaluation between two or more formulations provides information about in vivo performance. In a favorable decision regarding bioequivalence, the products are considered to have a similar therapeutic efficacy when used under the same therapeutic conditions. This paper reports the design, results and some important aspects involved in a bioequivalence study between two solid oral formulations from different manufacturers. Some important findings were the high intra-subject variability observed for Cmax and the variability observed between subject profiles, probably caused by the multi-unit type of formulations studied.

Tunable optical oscillator based on a DFB-MQW laser and a fiber loop reflector

In this paper, we report experimental results on the frequency control of an optical oscillator based on a single-cavity DFB-MQW laser and a fiber loop reflector. Self-pulsation frequency can be controlled by changing the step amplitude of the laser bias current.

Crystallization and preliminary X-ray crystallographic studies of the 13-fold symmetric portal protein of bacteriophage SPP1

Portal proteins are cyclical oligomers which play essential roles in bacteriophage pro-capsid formation, DNA packaging, and in connector formation. Bacteriophage SPP1 portal protein (gp6) is a turbine-like molecule with 13-fold symmetry [Dube et al. (1993) EMBO J. 12, 1303-1309]. The purified protein was crystallized with polyethylene glycol 400 as the precipitating agent using the vapor-diffusion method. Salt conditions were selected based on the properties of gp6 in different ionic environments. X-ray diffraction data up to a resolution of 7.85 A were measured from frozen crystals with orthorhombic space group C2221 and cell dimensions a = 180.5 (5), b = 223.5 (5), c = 417 (1) A. The asymmetric unit contains one tridecameric portal protein with 57.3 kDa subunits. The self-rotation searches confirm the 13-fold symmetry of the crystallized protein.