Safety of a compression stocking for patients with chronic venous insufficiency (CVI) and peripheral artery disease (PAD).

BACKGROUND: With increasing age, it is increasingly common for patients to develop both chronic venous insufficiency (CVI) and peripheral artery disease (PAD). While there are special compression bandage systems commercially available for individuals thus affected, appropriate compression stockings have previously not been available. In the present study, we investigated the safety and effectiveness of a type of compression stocking specifically designed for this patient group (VenoTrain® angioflow, Bauerfeind Germany, German compression class 1 with high stiffness). PATIENTS AND METHODS: In a prospective case series, we included patients with both CVI (C3-C5 disease according to CEAP classification) and PAD (ankle-brachial index of < 0.9 and > 0.5; absolute ankle systolic pressure of > 60 mmHg). Primary outcome measures consisted of 1) safety in terms of PAD, as determined by measuring acral pressure using acral photoplethysmography (APPG), and 2) effectiveness in terms of CVI symptoms, as assessed by using a suitable questionnaire (VVSymQ). RESULTS: Fifty patients were evaluated (mean age: 67.1; mean ankle-brachial index: 0.75 ± 0.77). Fifteen patients had stage IIa PAD (according to Fontaine); 15, stage IIb; the remainder, stage I disease. Thirty-one patients had stage C3 CVI (according to CEAP classification); 16 patients, stage C4; and three patients, stage C5 disease. Immediately after donning the medical compression stocking, systolic arterial pressure in the big toe increased significantly (from 83.3 mmHg ± 27.6 mmHg to 90.8 mmHg ± 24.1 mmHg) (p = 0.026). The VVSymQ score dropped significantly from 5.0 ± 4.95 points to 1.4 ± 2.26 points (p < 0.001), thus reflecting an improvement in CVI symptoms. CONCLUSIONS: The compression stocking tested herein is safe for individuals with an ankle brachial index ≥ 0.5. Skin damage was not observed.

Structure of the processive rubber oxygenase RoxA from Xanthomonas sp.

Rubber oxygenase A (RoxA) is one of only two known enzymes able to catalyze the oxidative cleavage of latex for biodegradation. RoxA acts as a processive dioxygenase to yield the predominant product 12-oxo-4,8-dimethyl-trideca-4,8-diene-1-al (ODTD), a tri-isoprene unit. Here we present a structural analysis of RoxA from Xanthomonas sp. strain 35Y at a resolution of 1.8 Å. The enzyme is a 75-kDa diheme c-type cytochrome with an unusually low degree of secondary structure. Analysis of the heme group arrangement and peptide chain topology of RoxA confirmed a distant kinship with diheme peroxidases of the CcpA family, but the proteins are functionally distinct, and the extracellular RoxA has evolved to have twice the molecular mass by successively accumulating extensions of peripheral loops. RoxA incorporates both oxygen atoms of its cosubstrate dioxygen into the rubber cleavage product ODTD, and we show that RoxA is isolated with O2 stably bound to the active site heme iron. Activation and cleavage of O2 require binding of polyisoprene, and thus the substrate needs to use hydrophobic access channels to reach the deeply buried active site of RoxA. The location and nature of these channels support a processive mechanism of latex cleavage.

MacA is a second cytochrome c peroxidase of Geobacter sulfurreducens.

The metal-reducing δ-proteobacterium Geobacter sulfurreducens produces a large number of c-type cytochromes, many of which have been implicated in the transfer of electrons to insoluble metal oxides. Among these, the dihemic MacA was assigned a central role. Here we have produced G. sulfurreducens MacA by recombinant expression in Escherichia coli and have solved its three-dimensional structure in three different oxidation states. Sequence comparisons group MacA into the family of diheme cytochrome c peroxidases, and the protein indeed showed hydrogen peroxide reductase activity with ABTS(-2) as an electron donor. The observed K(M) was 38.5 ± 3.7 µM H(2)O(2) and v(max) was 0.78 ± 0.03 µmol of H(2)O(2)·min(-1)·mg(-1), resulting in a turnover number k(cat) = 0.46 · s(-1). In contrast, no Fe(III) reductase activity was observed. MacA was found to display electrochemical properties similar to other bacterial diheme peroxidases, in addition to the ability to electrochemically mediate electron transfer to the soluble cytochrome PpcA. Differences in activity between CcpA and MacA can be rationalized with structural variations in one of the three loop regions, loop 2, that undergoes conformational changes during reductive activation of the enzyme. This loop is adjacent to the active site heme and forms an open loop structure rather than a more rigid helix as in CcpA. For the activation of the protein, the loop has to displace the distal ligand to the active site heme, H93, in loop 1. A H93G variant showed an unexpected formation of a helix in loop 2 and disorder in loop 1, while a M297H variant that altered the properties of the electron transfer heme abolished reductive activation.

Probing the reactivity of different forms of azurin by flavin photoreduction.

The reactivity of a variant of the blue copper protein, azurin from Pseudomonas aeruginosa, was investigated with laser flash photolysis and compared with the reactivity of the wild-type (WT) protein. The variant was obtained by changing the Cu ligating His117 for a glycine. The mutation creates a gap in the ligand shell of the Cu that can be filled with external ligands or water molecules. The crystal structure of the H117G variant is reported. It shows that the immediate surrounding of the Cu site in the variant exhibits less rigidity than in the WT protein and that the loop containing the Cu ligands Cys112, His117 and Met121 in the WT protein has gained flexibility in the H117G variant. Flash photolysis experiments were performed with 5-deazariboflavin and 8α-imidazolyl-(N-propylyl)-amino riboflavin as electron donors to probe the reactivity of WT and H117G azurin, and of H117G azurin for which the gap in the Cu co-ordination shell was filled with imidazole. 8α-Imidazolyl-(N-propylyl)-amino riboflavin appears one to two orders less efficient as a photo-flash reductant than 5-deazariboflavin. The reactivity of the H117G variant in the absence of external ligands appears to be 2.5-fold lower than the WT reactivity (second-order rate constants of 51 ± 2 × 10(7) m(-1) ·s(-1) versus 21 ± 1 × 10(7) m(-1) ·s(-1) ), whereas the addition of imidazole restores reactivity to above the WT level (71 ± 4 × 10(7) m(-1) ·s(-1) ). The differences are discussed in terms of structural modifications and changes in reorganizational energy and electronic coupling. Database Structural data are available in the Protein Data Bank under the accession number 3N2J.

TFA and EPA productivities of Nannochloropsis salina influenced by temperature and nitrate stimuli in turbidostatic controlled experiments.

The influence of different nitrate concentrations in combination with three cultivation temperatures on the total fatty acids (TFA) and eicosapentaenoic acid (EPA) content of Nannochloropsis salina was investigated. This was done by virtue of turbidostatic controlled cultures. This control mode enables the cultivation of microalgae under defined conditions and, therefore, the influence of single parameters on the fatty acid synthesis of Nannochloropsis salina can be investigated. Generally, growth rates decreased under low nitrate concentrations. This effect was reinforced when cells were exposed to lower temperatures (from 26 °C down to 17 °C). Considering the cellular TFA concentration, nitrate provoked an increase of TFA under nitrate limitation up to 70% of the biological dry mass (BDM). In contrast to this finding, the EPA content decreased under low nitrate concentrations. Nevertheless, both TFA and EPA contents increased under a low culture temperature (17 °C) compared to moderate temperatures of 21 °C and 26 °C. In terms of biotechnological production, the growth rate has to be taken into account. Therefore, for both TFA and EPA production, a temperature of 17 °C and a nitrate concentration of 1800 µmol L⁻¹ afforded the highest productivities. Temperatures of 21 °C and 26 °C in combination with 1800 µmol L⁻¹ nitrate showed slightly lower TFA and EPA productivities.

CcpA from Geobacter sulfurreducens is a basic di-heme cytochrome c peroxidase.

Bacterial di-heme cytochrome c peroxidases (CcpAs) protect the cell from reactive oxygen species by reducing hydrogen peroxide to water. The enzymes are c-type cytochromes, with both heme groups covalently attached to the protein chain via a characteristic binding motif. The genome of the dissimilatory metal-reducing bacterium Geobacter sulfurreducens revealed the presence of a ccpA gene and we isolated the gene product after recombinant expression in Escherichia coli. CcpA from G. sulfurreducens exhibited in vitro peroxidase activity with ABTS(2-) [2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)] as an electron donor, and the three-dimensional structure of the dimeric enzyme has been determined to high resolution. For activation, CcpA commonly requires reduction, with the exception of the Nitrosomonas europaea enzyme that retains its activity in the oxidized state. A G94K/K97Q/R100I triple point mutant was created to mimic the critical loop region of N. europaea CcpA, but its crystal structure revealed that the inactive, bis-histidinyl-coordinated form of the active-site heme group was retained. Subsequent mutational studies thus addressed an adjacent loop region, where a change in secondary structure accompanies the reductive activation of the enzyme. While an A124K/K128A double mutant did not show significant changes, the CcpA variants S134P/V135K and S134P led to a distortion of the loop region, accompanied by an opening of the active-site loop, leaving the enzyme in a constitutively active state.

Crystal packing of the c(6)-type cytochrome OmcF from Geobacter sulfurreducens is mediated by an N-terminal Strep-tag II.

The putative outer membrane c-type cytochrome OmcF from Geobacter sulfurreducens contains a single haem group and shows homology to soluble cytochromes c(6), a class of electron-transfer proteins that are typically found in cyanobacterial photosynthetic electron-transfer chains. OmcF was overexpressed heterologously in Escherichia coli as an N-terminal Strep-tag II fusion protein and isolated using streptactin-affinity chromatography followed by size-exclusion chromatography. The structure was solved by Fe SAD using data collected to a resolution of 1.86 A on a rotating copper-anode X-ray generator. In the crystal, packing interactions in one dimension were exclusively mediated through the Strep-tag II sequence. The tag and linker regions were in contact with three further monomers of OmcF, leading to a well defined electron-density map for this engineered and secondary-structure-free region of the molecule.

Crystallization of the extracellular rubber oxygenase RoxA from Xanthomonas sp. strain 35Y.

Rubber oxygenase A (RoxA) from Xanthomonas sp. strain 35Y is an extracellular dioxygenase that is capable of cleaving the double bonds of poly(cis-1,4-isoprene) into short-chain isoprene units with 12-oxo-4,8-dimethyl-trideca-4,8-diene-1-al (ODTD) as the major cleavage product. Crystals of the dihaem c-type cytochrome RoxA were grown by sitting-drop vapour diffusion using polyethylene glycol as a precipitant. RoxA crystallized in space group P2(1), with unit-cell parameters a = 72.4, b = 97.1, c = 101.1 A, beta = 98.39 degrees, resulting in two monomers per asymmetric unit. Diffraction data were collected to a limiting resolution of 1.8 A. Despite a protein weight of 74.1 kDa and only two iron sites per monomer, phasing was successfully carried out by multiple-wavelength anomalous dispersion.