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1.
Rev Geophys ; 58(4): e2019RG000678, 2020 Dec.
Article in English | MEDLINE | ID: mdl-33015673

ABSTRACT

We assess evidence relevant to Earth's equilibrium climate sensitivity per doubling of atmospheric CO2, characterized by an effective sensitivity S. This evidence includes feedback process understanding, the historical climate record, and the paleoclimate record. An S value lower than 2 K is difficult to reconcile with any of the three lines of evidence. The amount of cooling during the Last Glacial Maximum provides strong evidence against values of S greater than 4.5 K. Other lines of evidence in combination also show that this is relatively unlikely. We use a Bayesian approach to produce a probability density function (PDF) for S given all the evidence, including tests of robustness to difficult-to-quantify uncertainties and different priors. The 66% range is 2.6-3.9 K for our Baseline calculation and remains within 2.3-4.5 K under the robustness tests; corresponding 5-95% ranges are 2.3-4.7 K, bounded by 2.0-5.7 K (although such high-confidence ranges should be regarded more cautiously). This indicates a stronger constraint on S than reported in past assessments, by lifting the low end of the range. This narrowing occurs because the three lines of evidence agree and are judged to be largely independent and because of greater confidence in understanding feedback processes and in combining evidence. We identify promising avenues for further narrowing the range in S, in particular using comprehensive models and process understanding to address limitations in the traditional forcing-feedback paradigm for interpreting past changes.

2.
Biochim Biophys Acta ; 1797(9): 1617-26, 2010 Sep.
Article in English | MEDLINE | ID: mdl-20542012

ABSTRACT

High-field electron paramagnetic resonance (HF EPR) has been employed to investigate the primary electron donor electronic structure of Blastochloris viridis heterodimer mutant reaction centers (RCs). In these mutants the amino acid substitution His(M200)Leu or His(L173)Leu eliminates a ligand to the primary electron donor, resulting in the loss of a magnesium in one of the constituent bacteriochlorophylls (BChl). Thus, the native BChl/BChl homodimer primary donor is converted into a BChl/bacteriopheophytin (BPhe) heterodimer. The heterodimer primary donor radical in chemically oxidized RCs exhibits a broadened EPR line indicating a highly asymmetric distribution of the unpaired electron over both dimer constituents. Observed triplet state EPR signals confirm localization of the excitation on the BChl half of the heterodimer primary donor. Theoretical simulation of the triplet EPR lineshapes clearly shows that, in the case of mutants, triplet states are formed by an intersystem crossing mechanism in contrast to the radical pair mechanism in wild type RCs. Photooxidation of the mutant RCs results in formation of a BPhe anion radical within the heterodimer pair. The accumulation of an intradimer BPhe anion is caused by the substantial loss of interaction between constituents of the heterodimer primary donor along with an increase in the reduction potential of the heterodimer primary donor D/D+ couple. This allows oxidation of the cytochrome even at cryogenic temperatures and reduction of each constituent of the heterodimer primary donor individually. Despite a low yield of primary donor radicals, the enhancement of the semiquinone-iron pair EPR signals in these mutants indicates the presence of kinetically viable electron donors.


Subject(s)
Bacteriochlorophylls/chemistry , Electron Spin Resonance Spectroscopy/methods , Hyphomicrobiaceae/chemistry , Photosynthetic Reaction Center Complex Proteins/chemistry , Electron Transport , Mutation , Oxidation-Reduction , Protein Multimerization
3.
J R Army Med Corps ; 154(4): 243-4, 2008 Dec.
Article in English | MEDLINE | ID: mdl-19496369

ABSTRACT

Intra-abdominal lymphangiomas are rare benign tumours that usually arise in the mesentery of the small bowel. We present the case of an intra-abdominal lymphangioma that involved both the jejunum and its adjacent mesentery that ultrasound and CT scanning suggested was an ovarian tumour. Laparoscopy confirmed normal ovaries and a jejunal mass which was resected at laparotomy. This circumstance has very rarely been described in the literature and represents a diagnostic dilemma of which clinicians should be aware. Intra-abdominal lymphangioma should be included with other non-gynaecological diseases in the differential diagnosis of a pelvic mass, and requires a multi-specialty approach.


Subject(s)
Jejunal Neoplasms/diagnosis , Lymphangioma/diagnosis , Mesentery , Ovarian Neoplasms/diagnosis , Peritoneal Neoplasms/diagnosis , Abdominal Pain , Diagnosis, Differential , Female , Humans , Jejunal Neoplasms/surgery , Laparoscopy , Lymphangioma/surgery , Ovarian Neoplasms/surgery , Peritoneal Neoplasms/surgery , Tomography, X-Ray Computed , Young Adult
6.
J Magn Reson ; 150(1): 26-34, 2001 May.
Article in English | MEDLINE | ID: mdl-11330979

ABSTRACT

Benzoquinone (BQ), deuterobenzoquinone (d4-BQ), and hydroquinone (BQH2) are investigated in ethylene glycol by means of direct detection fast time-resolved EPR spectroscopy after laser flash photolysis. The development of the magnetization as a function of time and magnetic field is obtained and analyzed in terms of the Bloch equations and hyperfine parameters. The signals are attributed to the semiquinones BQH(*) and d4-BQH(*). The presence of 1,2-dihydroxyethyl radicals during the photolysis of BQ and d(4)-BQ is verified. No alkyl radicals are observed in solutions of BQ with excess BQH2. Detailed analysis of the chemically induced dynamic electron polarization spectra with respect to their development in time shows that polarization patterns of the semiquinones can be traced back to a superposition of triplet mechanism and radical pair mechanism, the latter arising from geminate T-pairs. Hence, two independent pathways for polarization are assumed: reaction of triplet benzoquinone with ethylene glycol leads to the semiquinone and dihydroxyethyl radicals with all signals in emission, whereas the reaction of triplet BQ and BQH2 yields two semiquinones exhibiting both net emissive and multiplet emissive/absorptive intensity distributions.

8.
Proc Natl Acad Sci U S A ; 92(17): 7789-93, 1995 Aug 15.
Article in English | MEDLINE | ID: mdl-11607572

ABSTRACT

Light-induced radical pairs in deuterated and deuterated plus 15N-substituted Synechococcus lividus cyanobacteria have been studied by transient EPR following pulsed laser excitation. Nuclear quantum beats are observed in the transverse electron magnetization at lower temperatures. Model calculations for the time profiles, evaluated at the high-field emissive maximum of the spectrum, indicate assignment of these coherences to nitrogen nuclei in the primary donor. Thorough investigation of the nuclear modulation patterns can provide detailed information on the electronic structure of the primary donor, providing insight into the mechanism of the primary events of plant photosynthesis.

9.
Proc Natl Acad Sci U S A ; 90(20): 9485-8, 1993 Oct 15.
Article in English | MEDLINE | ID: mdl-8415727

ABSTRACT

We report high-field continuous wave EPR spectra of P700+. in preparations obtained from deuterated cyanobacteria (Synechococcus lividus). Measurements were performed with photosystem I (PS-I) preparations, whole cells from cyanobacteria grown in 2H2O, and photosystem II (PS-II) preparations, as well as with protonated PS-I preparations. Because of the significantly improved resolution of our 140-GHz spectrometer (as compared with X- or Q-band EPR) the principal values of the g-tensor of the primary donor P700+. could be resolved and measured with high accuracy as g11 = 2.00304, g22 = 2.00262, and g33 = 2.00232. Other signals arising from Mn2+ and a dark signal from PS-II at g approximately 2.00266 are distinguished from the P700+. g-tensor powder pattern. The measured g values are compared with those of several bacterial reaction center donors.


Subject(s)
Cyanobacteria/physiology , Photosynthetic Reaction Center Complex Proteins/metabolism , Deuterium , Electron Spin Resonance Spectroscopy , In Vitro Techniques
10.
Can J Nurs Adm ; 6(2): 25-8, 30, 1993.
Article in English | MEDLINE | ID: mdl-8347653

ABSTRACT

This article documents the successful development of a computer-assisted process for systematic review of nursing policies and procedures at The Queen Elizabeth Hospital, Toronto, Ontario. Through broad staff input, policies and procedures are research-based yet grounded in the reality of the facility's nursing practice. Client-related standards are written as measurable, realistic statements of desired client outcomes, and as such are standards for client care. Policies and procedures have been rated according to the Canadian Council on Health Facilities Accreditation criteria (client centered, high risk, high volume, problem prone, interservice, outcome-related), so that important policies are easily identified to provide focus for quality assurance activities. The review process is structured so that over the course of a year, all policies are circulated for review by all levels of nursing staff.


Subject(s)
Management Information Systems , Manuals as Topic , Nursing Service, Hospital/organization & administration , Organizational Policy , Clinical Protocols , Professional Staff Committees , Quality Assurance, Health Care
11.
Proc Natl Acad Sci U S A ; 89(18): 8517-21, 1992 Sep 15.
Article in English | MEDLINE | ID: mdl-1528856

ABSTRACT

Spontaneous emission from reaction centers of photosynthetic bacteria has been recorded with a time resolution of 50 fs. Excitation was made directly into both the special-pair band (850 nm) and the Qx band of bacteriochlorophylls (608 nm). Rhodobacter sphaeroides R26, Rhodobacter capsulatus wild type, and four mutants of Rb. capsulatus were studied. In all cases the fluorescence decay was not single exponential and was well fit as a sum of two exponential decay components. The short components are in excellent agreement with the single component detected by measurements of stimulated emission. The origin of the nonexponential decay is discussed in terms of heterogeneity, the kinetic scheme, and the possibility of slow vibrational relaxation.


Subject(s)
Photosynthesis , Photosynthetic Reaction Center Complex Proteins/metabolism , Energy Transfer , Kinetics , Lasers , Spectrometry, Fluorescence
12.
Proc Natl Acad Sci U S A ; 88(24): 11202-6, 1991 Dec 15.
Article in English | MEDLINE | ID: mdl-1763033

ABSTRACT

The initial electron transfer in reaction centers from Rhodobacter sphaeroides R26 was studied by a subpicosecond transient pump-probe technique. The measured kinetics at various wavelengths were analyzed and compared with several mechanisms for electron transfer. An unambiguous determination of the initial electron transfer mechanism in reaction centers cannot be made by studying the anion absorption region (640-690 nm), due to the spectral congestion in this region. However, correlations between the stimulated emission decay of the excited state of the special pair, P*, at 926 nm and bleaching of the bacteriopheophytin Qx absorption at 545 nm suggest that the electron transfer at 283 K is dominated by a two-step sequential mechanism, whereas one-step superexchange and the two-step sequential mechanism have about equal contributions at 22 K.


Subject(s)
Photosynthetic Reaction Center Complex Proteins/metabolism , Rhodobacter sphaeroides/metabolism , Electron Transport , Kinetics , Models, Theoretical , Time Factors
13.
Proc Natl Acad Sci U S A ; 88(21): 9895-6, 1991 Nov 01.
Article in English | MEDLINE | ID: mdl-11607234

ABSTRACT

The characteristic electron spin polarized electron paramagnetic resonance (ESP EPR) signal observed in photosystem I (PSI) has been previously assigned to a radical pair composed of the oxidized primary donor and a reduced vitamin K1. Under conditions in which Bottin, H. & Setif, P. [(1991), Biochim. Biophys. Acta 105, 331-336] proposed that A1 is doubly reduced, the ESP EPR signal was not observed. Therefore, the ESP EPR signal can be directly attributed to A-1, and vitamin K1 can be assigned as this PSI acceptor. The ESP EPR signal was partially restored by removal of the chemical reductants.

14.
Biochemistry ; 29(35): 8030-2, 1990 Sep 04.
Article in English | MEDLINE | ID: mdl-2175644

ABSTRACT

The electron spin polarized (ESP) electron paramagnetic resonance (EPR) signal observed in spinach photosystem I (PSI) particles was examined in preparations depleted of vitamin K1 by solvent extraction and following biological reconstitution by the quinone. The ESP EPR signal was not detected in the solvent-extracted PSI sample but was restored upon reconstitution with either protonated or deuterated vitamin K1 under conditions that also restored electron transfer to the terminal PSI acceptors. Reconstitution using deuterated vitamin K1 resulted in a line narrowing of the ESP EPR signal, supporting the conclusion that the ESP EPR signals in the reconstituted samples arise from a radical pair consisting of the oxidized PSI primary donor, P700+, and reduced vitamin K1.


Subject(s)
Photosynthetic Reaction Center Complex Proteins/metabolism , Vitamin K 1/metabolism , Electron Spin Resonance Spectroscopy , Electron Transport , Oxidation-Reduction , Photochemistry , Photosynthetic Reaction Center Complex Proteins/radiation effects , Photosystem I Protein Complex
15.
Biochemistry ; 29(26): 6203-10, 1990 Jul 03.
Article in English | MEDLINE | ID: mdl-2169865

ABSTRACT

Electron paramagnetic resonance (EPR) has been used to investigate the cation and triplet states of Rhodobacter capsulatus reaction centers (RCs) containing amino acid substitutions affecting the primary donor, monomeric bacteriochlorophylls (Bchls), and the photoactive bacteriopheophytin (Bphe). The broadened line width of the cation radical in HisM200----Leu and HisM200----Phe reaction centers, whose primary donor consists of a Bchl-Bphe heterodimer, indicates a highly asymmetric distribution of the unpaired electron over the heterodimer. A T0 polarized triplet state with reduced yield is observed in heterodimer-containing RCs. The zero field splitting parameters indicate that this triplet essentially resides on the Bchl half of the heterodimer. The cation and triplet states of reaction centers containing HisM200----Gln, HisL173----Gln, GluL104----Gln, or GluL104----Leu substitutions are similar to those observed in wild type. Oligonucleotide-mediated mutagenesis has been used to change the histidine residues that are positioned near the central Mg2+ ions of the reaction center monomeric bacteriochlorophylls. Reaction centers containing serine substitutions at M180 and L153 or a threonine substitution at L153 have unaltered pigment compositions and are photochemically active. The cation and triplet states of HisL153----Leu reaction centers are similar to those observed in wild type. Triplet energy transfer to carotenoid is not observed at 100 K in HisM180----Arg chromatophores. These results have important implications for the structural requirements of tetrapyrrole binding and for our understanding of the mechanisms of primary electron transfer in the reaction center.


Subject(s)
Bacteriochlorophylls/genetics , Pheophytins/genetics , Photosynthetic Reaction Center Complex Proteins/genetics , Rhodospirillaceae/metabolism , Bacteriochlorophylls/metabolism , Electron Spin Resonance Spectroscopy , Electron Transport , Light-Harvesting Protein Complexes , Mutation , Oxidation-Reduction , Pheophytins/metabolism , Pheophytins/radiation effects , Photosynthetic Reaction Center Complex Proteins/metabolism , Photosynthetic Reaction Center Complex Proteins/radiation effects , Pyrroles/metabolism , Tetrapyrroles
16.
Am J Clin Nutr ; 51(2): 188-96, 1990 Feb.
Article in English | MEDLINE | ID: mdl-2137670

ABSTRACT

Previous studies indicate that limiting tyrosine and phenylalanine intake in the diet decreases tumor growth and metastasis. General health status, immune status, and platelet function were studied in nine healthy human subjects consuming low-protein foods supplemented with formula diets free of tyrosine and phenylalanine to maintain total daily intake of tyrosine at 2.4 mg/kg body wt and phenylalanine at 3.5 mg/kg body wt. This regimen decreased plasma tyrosine (p less than 0.05) but not phenylalanine. Blood indicators of protein status were not changed. Platelet aggregation decreased in response to adenosine diphosphate and platelet activating factor in seven of nine subjects. Natural killer, T-helper, and T-cytotoxic/suppressor lymphocyte numbers proportionally increased relative to neutrophils (p less than 0.05). Natural killer cell activity increased in six of nine subjects. Increased natural killer cell activity and decreased platelet aggregation are two indices associated with decreased tumor growth and metastasis.


Subject(s)
Diet , Immunocompetence , Phenylalanine/administration & dosage , Tyrosine/administration & dosage , Body Composition , Dietary Proteins/administration & dosage , Female , Humans , Killer Cells, Natural/immunology , Male , Platelet Aggregation , T-Lymphocytes, Cytotoxic/immunology , T-Lymphocytes, Helper-Inducer/immunology , T-Lymphocytes, Regulatory/immunology
17.
Biochemistry ; 29(4): 899-907, 1990 Jan 30.
Article in English | MEDLINE | ID: mdl-2187533

ABSTRACT

The effect of an external electric field on the optical absorption spectra of wild-type Rhodobacter capsulatus and two Rb. capsulatus reaction centers that have been genetically modified through site-directed mutagenesis (HisM200----LeuM200 and HisM200----PheM200) was measured at 77 K. The two genetically modified reaction centers replace histidine M200, the axial ligand to the M-side bacteriochlorophyll of the special pair, with either leucine or phenylalanine. These substitutions result in the replacement of the M-side bacteriochlorophyll with bacteriopheophytin, forming a bacteriochlorophyll-bacteriopheophytin heterodimer. The magnitude of the change in dipole moment from the ground to excited state (delta mu app) and the angle delta between the Qy transition moment and the direction of delta mu app were measured for the special pair absorption band for all three reaction centers. The values for delta mu app and delta obtained for wild-type Rb. capsulatus (delta mu app = 6.7 +/- 1.0 D, delta = 38 +/- 3 degrees) were the same within experimental error as those of Rhodobacter sphaeroides and Rhodopseudomonas viridis. The values for delta mu app and delta obtained for the red-most Stark band of both heterodimers were the same, but delta mu was substantially different from that of wild-type reaction centers (HisM200----LeuM200, delta mu app greater than or equal to 14.1 D and delta = 33 +/- 3 degrees; HisM200----PheM200, delta mu app greater than or equal to 15.7 D and delta = 31 +/- 4 degrees).(ABSTRACT TRUNCATED AT 250 WORDS)


Subject(s)
Bacterial Proteins/genetics , Electromagnetic Fields , Histidine , Leucine , Light-Harvesting Protein Complexes , Mutation , Optics and Photonics , Phenylalanine , Photosynthetic Reaction Center Complex Proteins , Rhodopseudomonas/genetics , Spectrum Analysis/methods
18.
Proc Natl Acad Sci U S A ; 86(12): 4335-9, 1989 Jun.
Article in English | MEDLINE | ID: mdl-2543969

ABSTRACT

The orientation of the principal axes of the primary electron donor triplet state measured in single crystals of photosynthetic reaction centers is compared to the x-ray structures of the bacteria Rhodobacter (Rb.) sphaeroides R-26 and Rhodopseudomonas (Rps.) viridis. The primary donor of Rps. viridis is significantly different from that of Rb. sphaeroides. The measured directions of the axes indicate that triplet excitation is almost completely localized on the L-subunit half of the dimer in Rps. viridis but is more symmetrically distributed (approximately 63% on the L half of the special pair and approximately 37% on the M half) on the dimeric donor in Rb. sphaeroides R-26. The large reduction of the zero field splitting parameters relative to monomeric bacteriochlorophyll triplet in vitro suggests significant participation of asymmetrical charge transfer electronic configurations in the special pair triplet state of both organisms (approximately 23% in Rps. viridis and approximately 13% in Rb. sphaeroides).


Subject(s)
Bacterial Proteins/metabolism , Photosynthesis , Rhodobacter sphaeroides/metabolism , Rhodopseudomonas/metabolism , Electron Spin Resonance Spectroscopy , Electron Transport , Light-Harvesting Protein Complexes , Photosynthetic Reaction Center Complex Proteins , Species Specificity
19.
J Gen Microbiol ; 134(3): 743-9, 1988 Mar.
Article in English | MEDLINE | ID: mdl-3141574

ABSTRACT

The existence of subgroups within Bacillus megaterium has been reported previously on the basis of DNA-DNA hybridization and DNA base composition studies. In this study the strains used to define these subgroups have been reanalysed by pyrolysis gas-liquid chromatography. The resultant two-group classification of the test strains was directly comparable with that obtained from the previous nucleic acid analyses at the between-group level. However, comparisons of the test strains at the within-group level proved less successful.


Subject(s)
Bacillus megaterium/classification , Chromatography, Gas , DNA, Bacterial/classification , Nucleic Acid Hybridization , Base Composition , Sequence Homology, Nucleic Acid
20.
J Appl Bacteriol ; 64(1): 79-88, 1988 Jan.
Article in English | MEDLINE | ID: mdl-3127372

ABSTRACT

The discrimination of a set of 53 strains, taken from four closely related Bacillus species (Bacillus subtilis, B. pumilus, B. licheniformis and B. amyloliquefaciens), was examined using pyrolysis mass spectrometry. Strains were grown on six different media to examine the effect of media variation, especially batch-to-batch variation of a single medium, on the pyrolysis mass spectra and strain discrimination achieved. Long-term reproducibility over a period of 14 months was also examined. It was shown that batch-to-batch media variation is insufficient to affect spectra and strain discrimination significantly, but different media types do affect this. It was shown that species groups could still be recovered from the data, however, with an appropriate data-handling system. It was not possible to directly compare spectra produced 14 months apart, but the strain and species discrimination achieved using each data-set were highly comparable.


Subject(s)
Bacillus/classification , Bacillus/analysis , Bacillus/isolation & purification , Bacillus subtilis/analysis , Bacillus subtilis/classification , Bacillus subtilis/isolation & purification , Culture Media , Hot Temperature , Mass Spectrometry/instrumentation , Time Factors
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