| 1. |
- Adrait, Annie, et al.
(författare)
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EPR studies on a stable sulfinyl radical observed in the iron-oxygen reconstituted Y177F/I263C protein double mutant of ribonucleotide reductase from mouse
- 2002
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 41:20, s. 6510-6516
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Tidskriftsartikel (refereegranskat)abstract
- Ribonucleotide reductase (RNR) catalyzes the biosynthesis of deoxyribonucleotides. The active enzyme contains a diiron center and a tyrosyl free radical required for enzyme activity. The radical is located at Y177 in the R2 protein of mouse RNR. The radical is formed concomitantly with the μ-oxo-bridged diferric center in a reconstitution reaction between ferrous iron and molecular oxygen in the protein. EPR at 9.6 and 285 GHz was used to investigate the reconstitution reaction in the double-mutant Y177F/I263C of mouse protein R2. The aim was to produce a protein-linked radical derived from the Cys residue in the mutant protein to investigate its formation and characteristics. The mutation Y177F hinders normal radical formation at Y177, and the I263C mutation places a Cys residue at the same distance from the iron center as Y177 in the native protein. In the reconstitution reaction, we observed small amounts of a transient radical with a probable assignment to a peroxy radical, followed by a stable sulfinyl radical, most likely located on C263. The unusual radical stability may be explained by the hydrophobic surroundings of C263, which resemble the hydrophobic pocket surrounding Y177 in native protein R2. The observation of a sulfinyl radical in RNR strengthens the relationship between RNR and another free radical enzyme, pyruvate formate-lyase, where a similar relatively stable sulfinyl radical has been observed in a mutant. Sulfinyl radicals may possibly be considered as stabilized forms of very short-lived thiyl radicals, proposed to be important intermediates in the radical chemistry of RNR.
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| 2. |
- Amombo Noa, Francoise Mystere, 1988, et al.
(författare)
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A unified topology approach to dot-, rod-, and sheet-MOFs
- 2021
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Ingår i: Chem. - : Elsevier BV. - 2451-9294 .- 2451-9308. ; 7:9, s. 2491-2512
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Tidskriftsartikel (refereegranskat)abstract
- Metal-organic frameworks made from multi-metal-ion units in the shape of clusters and rods (termed dot-MOFs and rod-MOFs) are well known. Here, we introduce MOFs with multi-metallic units in the form of sheets-sheet-MOFs. We show exemplars of all three types of units based on structures containing Y3+, Ce3+, or Gd3+ linked by benzene1,2,4,5-tetracarboxylate to give crystals of a dot-MOF in H2NMe2[Y(b-tec)(H2O)] CTH-14, a sheet-MOF in [Ce-3(btec)(Hbtec)(OAc)(HCO2)] CTH-15, and a rod-MOF in 4,4'-azopyridinium[Gd-2(btec)(2)] CTH-16. Cyclic voltammetry shows that CTH-15 stabilizes Ce(IV). Given the fact that sheet-MOFs represent an intellectual advance in the evolution of MOFs, a unified approach is proposed for the topological classification of dot-, rod-, and sheet-MOFs. It is suggested that the stability ofMOFs follow in the trend dot < rod < sheet. For CTH-14-16, the sheet- and the rod-MOF have higher thermal stability. We suggest sheet-MOFs as an additional strategy for making robust MOFs.
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| 3. |
- Andersson, Charlotta S., 1979-, et al.
(författare)
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The manganese ion of the heterodinuclear Mn/Fe cofactor in Chlamydia trachomatis ribonucleotide reductase R2c is located at metal position 1.
- 2012
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 134:1, s. 123-125
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Tidskriftsartikel (refereegranskat)abstract
- The essential catalytic radical of Class-I ribonucleotide reductase is generated and delivered by protein R2, carrying a dinuclear metal cofactor. A new R2 subclass, R2c, prototyped by the Chlamydia trachomatis protein was recently discovered. This protein carries an oxygen-activating heterodinuclear Mn(II)/Fe(II) metal cofactor and generates a radical-equivalent Mn(IV)/Fe(III) oxidation state of the metal site, as opposed to the tyrosyl radical generated by other R2 subclasses. The metal arrangement of the heterodinuclear cofactor remains unknown. Is the metal positioning specific, and if so, where is which ion located? Here we use X-ray crystallography with anomalous scattering to show that the metal arrangement of this cofactor is specific with the manganese ion occupying metal position 1. This is the position proximal to the tyrosyl radical site in other R2 proteins and consistent with the assumption that the high-valent Mn(IV) species functions as a direct substitute for the tyrosyl radical.
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| 4. |
- Arm, Maria, et al.
(författare)
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Gasbildning i aska
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)
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| 5. |
- Bodin, Theo, et al.
(författare)
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Survey context and question wording affects self reported annoyance due to road traffic noise: a comparison between two cross-sectional studies.
- 2012
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Ingår i: Environmental health : a global access science source. - 1476-069X. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: BACKGROUND: Surveys are a common way to measure annoyance due to road traffic noise, but the method has some draw-backs. Survey context, question wording and answer alternatives could affect participation and answers and could have implications when comparing studies and/or performing pooled analyses. The aim of this study was to investigate the difference in annoyance reporting due to road traffic noise in two types of surveys of which one was introduced broadly and the other with the clearly stated aim of investigating noise and health METHODS: Data was collected from two surveys carried out in the municipality of Malmo, southern Sweden in 2007 and 2008 (n = 2612 and n = 3810). The first survey stated an aim of investigating residential environmental exposure, especially noise and health. The second survey was a broad public health survey stating a broader aim. The two surveys had comparable questions regarding noise annoyance, although one used a 5-point scale and the other a 4-point scale. We used geographic information systems (GIS) to assess the average road and railway noise (LAeq,24h) at the participants' residential address. Logistic regression was used to calculate odds ratios for annoyance in relation to noise exposure. RESULTS: Annoyance at least once a week due to road traffic noise was significantly more prevalent in the survey investigating environment and health compared to the public health survey at levels >45 dB(A), but not at lower exposure levels. However no differences in annoyance were found when comparing the extreme alternatives "never" and "every day". In the study investigating environment and health, "Noise sensitive" persons were more likely to readily respond to the survey and were more annoyed by road traffic noise compared to the other participants in that survey. CONCLUSIONS: The differences in annoyance reporting between the two surveys were mainly due to different scales, suggesting that extreme alternatives are to prefer before dichotomization when comparing results between the two. Although some findings suggested that noise-sensitive individuals were more likely to respond to the survey investigating noise and health, we could not find convincing evidence that contextual differences affected either answers or participation.
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| 6. |
- Davydov, Albert, et al.
(författare)
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Chemical reduction of the diferric/radical center in protein R2 from mouse ribonucleotide reductase is independent of the proposed radical transfer pathway
- 2002
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Ingår i: Inorganica Chimica Acta. - 0020-1693 .- 1873-3255. ; 331:1, s. 65-72
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Tidskriftsartikel (refereegranskat)abstract
- The rates of reduction of the diferric/radical center in mouse ribonucleotide reductase protein R2 were studied by light absorption and EPR in the native protein and in three point mutants of conserved residues involved in the proposed radical transfer pathway (D266A, W103Y) or in the unstructured C terminal domain (Y370W). The pseudo-first order rate constants for chemical reduction of the tyrosyl radical and diferric center by hydroxyurea, sodium dithionite or the dihydro form of flavin adenine dinucleotide, were comparable with or higher (particularly D266A, by dithionite) than in native R2. Molecular modeling of the D266A mutant showed that the iron/radical site should be more accessible for external reductants in the mutant than in native R2. The results indicate that no specific pathway is required for the reduction. The dihydro form of flavin adenine dinucleotide was found to be a very efficient reductant in the studied proteins compared to dithionite alone. The EPR spectra of the mixed-valent Fe(II)Fe(III) sites formed by chemical reduction in the D266A and W103Y mutants were clearly different from the spectrum observed in the native protein, indicating that the structure of the diferric site was affected by the mutations, as also suggested by the modeling study. No difference was observed between the mixed-valent EPR spectra generated by chemical reduction in Y370W mutant and native mouse R2 protein
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| 7. |
- Åhlén, Michelle, et al.
(författare)
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Pore size effect of 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene-based metal-organic frameworks for enhanced SF 6 adsorption with high selectivity
- 2022
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 343
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic greenhouse gas emission poses as serious threat to our environment and it is therefore of utmost importance that efficient systems are developed to mitigate these issues. SF6, in particular, has attracted more attention in recent years due to its global warming potential which severely exceeds that of CO2. In this study we present the SF6 sorption properties of four highly porous 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene-based (TBAPy4−) metal-organic frameworks containing either ytterbium(III), thulium(III), cerium(III), or hafnium(IV). These MOFs can be synthesized with high crystallinity in as little as 5 h and were found to have good SF6 uptakes due to their suitable pore size. The SF6 uptake of the Yb-TBAPy MOF reached 2.33 mmol g−1 with high Henry's law SF6-over-N2 selectivity of ∼80 at 1 bar and 293 K. The TBAPy-MOFs were also found to have good chemical stability and good cyclic SF6 sorption stability with fast SF6 uptake. These TBAPy-MOFs possesses many of the properties desired for an efficient SF6 sorbent and may be suitable sorbents for further development, including sorbent processing for industrial applications.
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| 8. |
- Öhrström, Evy, 1946, et al.
(författare)
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Effects of road traffic noise on sleep – studies on children and adults.
- 2006
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Ingår i: Journal of Environmental Psychology. - : Elsevier BV. - 0272-4944. ; 26:2, s. 116-126
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Tidskriftsartikel (refereegranskat)abstract
- Socio-acoustic studies were conducted in residential areas in Sweden exposed to different levels of road traffic noise. The objectives were to evaluate exposure–effect relationships between road traffic noise and sleep quality and to compare sleep assessed by sleep logs and wrist-actigraphy for children and parents. The main study involved interviews with 160 children (9–12 years old) and 160 parents. Half of the families also participated in an in-depth study in which their sleep was registered with sleep logs and wrist-actigraphy. For parents the results demonstrate a significant exposure–effect relationship between noise levels from road traffic and the following sleep parameters: sleep quality, awakenings, the habit of keeping windows closed at night and perceived interference with road traffic noise. For children a significant exposure–effect relationship was found between road traffic noise and sleep quality as well as problems with daytime sleepiness. Results from the in-depth study showed that children had better perceived sleep quality and fewer awakenings than parents, although sleep assessed by wrist-actigraphy indicated a better sleep for parents.
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| 9. |
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| 10. |
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| 11. |
- Öhrström, Evy, et al.
(författare)
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Undersökning av hälsoeffekter av buller från vägtrafik, tåg och flyg i Lerums kommun
- 2005
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- En miljömedicinsk undersökning genomfördes bland delar av befolkningen i Lerums kommun under våren 2004. Målsättningen var att kartlägga förekomsten av hälsoeffekter av buller från vägtrafik, tåg och flyg, att utarbeta metodik för bestämning av individuell bullerexponering baserad på GIS-metodik (geografiska informationssystem) samt att pröva och ge förslag till nya indikatorer lämpade för uppföljning av förekomst av hälsorelaterade effekter av buller från trafik. Undersökningen har finansierats med medel från Socialstyrelsen, Naturvårdsverket, Länsstyrelsen i Västra Götalands län, RUS (Regionalt uppföljningssystem) samt Lerums kommun. Lönemedel för projektledningen har dessutom delvis finansierats inom VMC (Västra Götalandsregionens miljömedicinska centrum).
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| 12. |
- Öhrström, Maria, 1971-
(författare)
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Biophysical investigations of ribonucleotide reductase : Activation and inhibition mechanisms
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ribonucleotide reductase (RNR) is the enzyme responsible for de novo synthesis of deoxyribonucleotides, needed for both synthesis and repair of cellular DNA. The RNRs known so far are divided into three distinct classes; I, II and III. The conventional class I enzyme is composed of two separate subunits. The larger R1 subunit contains the active site, whereas the smaller R2 subunit contains a system specialized in forming, transporting and stabilizing a tyrosyl free radical. Recently a new class Ic RNR was discovered in the bacterium Chlamydia trachomatis. It differs from the conventional class Ia and b RNRs in that it has a phenylalanine at the otherwise conserved tyrosyl radical harboring residue in its R2 subunit. Additionally the metal cluster shows some unusual aspects, of which the most striking perhaps is that the most red-ox active form is a mixed Mn-Fe cluster, instead of the normal Fe-Fe counterpart. In this work several biochemical and biophysical methods were used to study activation and inhibition mechanisms in RNR from various class I species. The results from studying the oxygen activation confirm the role of the iron ligand E238 as a key residue for controlling the outcome of the reaction in E. coli protein R2. The finding of a stable sulfinyl radical after reconstitution of the R2 Y177F/I263C variant from mouse indicates that sulfinyl radicals may possibly be considered as stabilized forms of very short-lived thiyl radicals, proposed to be important in the radical chemistry of RNR. The investigation of the role of the proposed radical transfer pathway during chemical reduction of the iron/radical center shows that no specific pathway is required for the reduction of protein R2 from mouse. The results from inhibition studies of C. trachomatis demonstrate that the same mechanism of inhibition functions on this new class Ic RNR, however less efficiently than in class Ia and b.
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| 13. |
- Öhrström, Maria, et al.
(författare)
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Inhibition of chlamydial class Ic ribonucleotide reductase by C-terminal peptides from protein R2
- 2011
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Ingår i: Journal of Peptide Science. - : Wiley. - 1075-2617 .- 1099-1387. ; 17:11, s. 756-762
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Tidskriftsartikel (refereegranskat)abstract
- Chlamydia trachomatis ribonucleotide reductase (RNR) is a class Ic RNR. It has two homodimeric subunits: proteins R1 and R2. Class Ic protein R2 in its most active form has a manganese-iron metal cofactor, which functions in catalysis like the tyrosyl radical in classical class Ia and Ib RNRs. Oligopeptides with the same sequence as the C-terminus of C. trachomatis protein R2 inhibit the catalytic activity of C. trachomatis RNR, showing that the class Ic enzyme shares a similar highly specific inhibition mechanism with the previously studied radical-containing class Ia and Ib RNRs. The results indicate that the catalytic mechanism of this class of RNRs with a manganese-iron cofactor is similar to that of the tyrosyl-radical-containing RNRs, involving reversible long-range radical transfer between proteins R1 and R2. The competitive binding of the inhibitory R2-derived oligopeptide blocks the transfer pathway. We have constructed three-dimensional structure models of C. trachomatis protein R1, based on homologous R1 crystal structures, and used them to discuss possible binding modes of the peptide to protein R1. Typical half maximal inhibitory concentration values for C. trachomatis RNR are about 200 µ m for a 20-mer peptide, indicating a less efficient inhibition compared with those for an equally long peptide in the Escherichia coli class Ia RNR. A possible explanation is that the C. trachomatis R1/R2 complex has other important interactions, in addition to the binding mediated by the R1 interaction with the C-terminus of protein R2.
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| 14. |
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