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The primary donor in single crystals of photosystem I (PS I) obtained from the thermophilic cyanobacterium Synechococcus elongatus is investigated by EPR and ENDOR techniques. The cation radical %@mt;sys@%P%@sx@%700%@be@%+•%@sxx@%%@mx@% was generated chemically or photolytically in the single crystals, and angular dependent spectra were obtained at a temperature of 100 K in the frozen state. The principal values and corresponding axes orientations were determined for three different proton hyperfine coupling (hfc) tensors. On the basis of the tensor magnitudes, their symmetry, and the relative orientations of their axes, they were assigned to the protons of three methyl groups of a single chlorophyll (Chl) a molecule. From X-ray crystallography of PS I single crystals, it is known that P700 is structurally a chlorophyll dimer (Klukas et al., J. Biol. Chem. 1999, 274, 7361). The EPR/ENDOR experiments show that the second chlorophyll half carries no or very little (≤15%) spin density. The molecular plane of the spin-carrying Chl a molecule in %@mt;sys@%P%@sx@%700%@be@%+•%@sxx@%%@mx@% is parallel to the crystallographic c axis. From the orientation of the hf tensors of the methyl groups with respect to this axis, the orientation of the Chl a molecule could be determined. The orientation of this Chl a is very similar to that of the two symmetrically placed bacteriochlorophyll molecules forming the primary donors P865 and P960 in the RC of the purple bacteria Rhodobacter sphaeroides and Rhodopseudomonas viridis, respectively. These results indicate a structural similarity of the electron donors in purple bacteria and photosystem I and point to a common evolutionary origin of both types of reaction centers.

An improved electron density map of photosystem I (PSI) calculated at 4-A resolution yields a more detailed structural model of the stromal subunits PsaC, PsaD, and PsaE than previously reported. The NMR structure of the subunit PsaE of PSI from Synechococcus sp. PCC7002 (Falzone, C. J., Kao, Y.-H., Zhao, J., Bryant, D. A., and Lecomte, J. T. J. (1994) Biochemistry 33, 6052-6062) has been used as a model to interpret the region of the electron density map corresponding to this subunit. The spatial orientation with respect to other subunits is described as well as the possible interactions between the stromal subunits. A first model of PsaD consisting of a four-stranded beta-sheet and an alpha-helix is suggested, indicating that this subunit partly shields PsaC from the stromal side. In addition to the improvements on the stromal subunits, the structural model of the membrane-integral region of PSI is also extended. The current electron density map allows the identification of the N and C termini of the subunits PsaA and PsaB. The 11-transmembrane alpha-helices of these subunits can now be assigned uniquely to the hydrophobic segments identified by hydrophobicity analyses.

An improved electron density map of photosystem I from Synechococcus elongatus calculated at 4-A resolution for the first time reveals a second phylloquinone molecule and thereby completes the set of cofactors constituting the electron transfer system of this iron-sulfur type photosynthetic reaction center: six chlorophyll a, two phylloquinones, and three Fe4S4 clusters. The location of the newly identified phylloquinone pair, the individual plane orientations of these molecules, and the resulting distances to other cofactors of the electron transfer system are discussed and compared with those determined by magnetic resonance techniques.

The catalytic center (CC) of water oxidation in photosystem II passes through four stepwise increased oxidized states (S(0)-S(4)) before O(2) evolution takes place from 2H(2)O in the S(4) --> S(0) transition. The pattern of the release of the four protons from the CC cannot be followed directly in the medium, because proton release from unknown amino acid residues also takes place. However, pH-independent net charge oscillations of 0:0:1:1 in S(0):S(1):S(2):S(3) have been considered as an intrinsic indicator for the H(+) release from the CC. The net charges have been proposed to be created as the charge difference between electron abstraction and H(+) release from the CC. Then the H(+) release from the CC is 1:0:1:2 for the S(0) --> S(1) --> S(2) --> S(3) --> S(0) transition. Strong support for this conclusion is given in this work with the analysis of the pH-dependent pattern of H(+) release in the medium measured directly by a glass electrode between pH 5.5 and 7.2. Improved and crystallizable photosystem II core complexes from the cyanobacterium Synechococcus elongatus were used as material. The pattern can be explained by protons released from the CC with a stoichiometry of 1:0:1:2 and protons from an amino acid group (pK approximately 5.7) that is deprotonated and reprotonated through electrostatic interaction with the oscillating net charges 0:0:1:1 in S(0):S(1):S(2):S(3). Possible water derivatives that circulate through the S states have been named.

Background & Aims: In pancreatitis, a key role has been attributed to the inappropriate conversion of trypsinogen to trypsin. Recently, two mutations of the cationic trypsinogen gene were found in families with hereditary pancreatitis. This study was conducted to determine the spectrum and frequency of cationic trypsinogen mutations in unrelated patients with idiopathic or hereditary chronic pancreatitis (CP). Methods: DNA samples from 44 unrelated children and adolescents with CP (30 patients with idiopathic CP and 14 with hereditary CP) and from 56 family members were investigated. The cationic trypsinogen gene was screened for mutations by single-strand conformation polymorphism analysis and DNA sequencing. Results: A mutation in the cationic trypsinogen gene was detected in 5 patients: in 2 patients with a family history of CP and in 3 patients with idiopathic CP. In 1 patient the formerly described R122H mutation was detected. In 4 patients a hitherto unknown mutation was found at the signal peptide cleavage site leading to an alanine to valine exchange in codon 16. The mutations were inherited in all cases. In 95 unrelated control individuals the A16V mutation was not found. Conclusions: Heterozygosity for the A16V mutation is strongly associated with CP. These results indicate that a significant percentage of patients with idiopathic CP may have a genetic basis for their disorder; therefore, genetic testing should be included in the diagnostic evaluation of these patients. GASTROENTEROLOGY 1999;117:7-10

Cytochrome b, DNA Sequence, Polymerase Chain Reaction (PCR), Molecular Evolution, Procellariidae The cytochrome b gene of three European taxa of the family of Procellariidae was amplified from total DNA and sequenced. The sequence comparison shows that the Fulmar (Fulmarus glacialis) is significantly distinct from shearwaters, whereas Cory’s (Calonectris diomedea) and Manx Shearwater (Puffinus puffinus) are closely related. Although the populations of C. dio­medea can be distinguished morphologically, the sequences of cyt b differ only slightly between the Atlantic and Mediterranean subspecies (i.e. C. d. borealis versus C. d. diomedea) and do not reveal other population differences within subspecies.

The reaction sequence between the primary electron acceptor, the oxidized Chlorophyll-aII, and the terminal electron donor, the water splitting enzyme system S, is being described in the range from nanoseconds to milliseconds. For the cleavage of water Chlorophyll-aII+ extracts four electrons in four turnovers from the enzyme system S responsible for the water oxidation. For each extraction the electron is moved step by step along the chain that connects the Chlorophyll-aII center with that of S. Beginning with the transfer from the immediate donor, D1, to Chl-aII+, the subsequent transfer from D2 to D1+ ends in the electron transfer from S to D2+. This final act establishes in S the oxidizing equivalent, probably in the form of oxidized manganese. Coupled with these acts is an intrinsic proton release and a surplus charge formation. After the generation of the 4th oxidizing equivalent in a concerted final action the evolution of O2 from water takes place. Correlations between the events are described quantitatively.

The efficacy and safety of 25 mg pyrimethamine plus 500 mg sulfadoxine given twice a week in preventing relapses of AIDS-related toxoplasmic encephalitis was evaluated in an open study. The 56 HIV-infected patients evaluated had responded to intensive treatment with pyrimethamine/clindamycin prior to starting the present prophylactic regimen. Four patients (7 %) experienced relapse while on pyrimethamine/sulfadoxine. The probability of freedom from relapse was >90 % for 12 months and >80 % for 24 months. Side effects comprised mild or moderate allergic reactions which occurred in 23 patients (41 %), leading to discontinuation in four patients (7%). Forty-nine of the 56 patients did not have a history ofPneumocystis carinii pneumonia and did not receive antiparasitic prophylaxis other than pyrimethamine/sulfadoxine; two of them (4 %) developed pneumocystosis. The probability of freedom from pneumocystosis was about 90 % for 24 months. Pyrimethamine/sulfadoxine twice a week appears to be a promising regimen for prevention of toxoplasmic encephalitis, and also appears to provide protection againstPneumocystis carinii pneumonia. Although allergic reactions are usually mild and disappear on continuation, they may limit the value of this regimen.

In an 84‐year‐old man cryptococcosis with a pronounced osteomyelitic course (involvement of a rib, two thoracic vertebrae, the sacrum and a femur) was diagnosed histologically post mortem, thus directing attention to cryptococcosis in advanced age. The presumptive chronic course of the Cryptococcus neoformans (Cr. n.)infection in this patient was ascribed to chronic kidney failure, diabetes mellitus and chronic obstructive lung disease. Special reference is made to the mycological and radiological diagnosis of cryptococcosis of the bones as well as to its pathogenesis, therapy and epidemiology. Am Beispiel einer bei einem 84‐Jährigen post mortem histologisch diagnostizierten Cryptococcose mit betont osteomyelitischem Verlauf (Befall einer Rippe, zweier Brustwirbel, des Kreuzbeins und eines Femur) wird in pathogenetischer und diagnostischer Sicht auf die Cryptococcose im fortgeschrittenen Alter aufmerksam gemacht. Für den vermutlich chronischen Verlauf dieser Cryptococcus neoformans‐Infektion werden als ausschlaggebende Grundkrankheiten eine chronische Nierenerkrankung, ein Diabetes mellitus und eine chronisch obstruktive Lungenerkrankung verantwortlich gemacht. Besondere Beachtung verdienen Hinweise auf die mykologische und röntgenologische Diagnostik des Knochenbefalls bei Cryptococcose. Auf die Therapie und Epidemiologic der Cryptococcose wird hingewiesen.

To investigate the contribution of hydrophobic residues to the molecular recognition of cytochrome c with cytochrome oxidase, we mutated several hydrophobic amino acids exposed on subunit II of the Paracoccus denitrificans oxidase. KM and kcat values and the bimolecular rate constant were determined under steady- or presteady-state conditions, respectively. We present evidence that Trp-121 which is surrounded by a hydrophobic patch is the electron entry site to oxidase. Mutations in this cluster do not affect the binding of cytochrome c as the KM remains largely unchanged. Rather, the kcat is reduced, proposing that these hydrophobic residues are required for a fine tuning of the redox partners in the initial collisional complex to obtain a configuration optimal for electron transfer.

The gene coding for subunit IV of the cytochrome c oxidase in Paracoccus denitrificans has been cloned and sequenced. The derived amino acid sequence shows no significant homology to any known protein. Gene deletion has no consequences for the integrity of the complex and its spectral and enzymatic properties. Complementation of the deletion mutant in trans results in expression of subunit IV; sequence analysis of the 5'-noncoding region leads to the identification of a putative promoter sequence.

Oxygen evolution and reduction kinetics of the photooxidized Chl-aII+ have been measured in oxygen-evolving complexes from the thermophilic cyanobacterium Synechococcus sp.

The light-induced, charge-separated state %@mt;sys@%P%@sx@%700%@be@%•+%@sxx@%%@mx@% %@mt;sys@%A%@sx@%1%@be@%•-%@sxx@%%@mx@% in single crystals of Photosystem I (PSI) from the cyanobacterium Synechococcus elongatus is investigated with transient, direct-detection EPR spectroscopy. The orientation of the phylloquinone head group of A1 within the PSI reaction center is determined from the orientation dependence of the spin-polarized X-band EPR spectrum of the radical pair %@mt;sys@%P%@sx@%700%@be@%•+%@sxx@%%@mx@% %@mt;sys@%A%@sx@%1%@be@%•-%@sxx@%%@mx@% made up of the primary donor, P700, and the acceptor, A1. From the angular dependence of the overall spin-polarization pattern an upper limit ∠(c, zd) ≤ 30° is evaluated for the angle between the crystallographic c-axis, collinear with the membrane normal, and the dipolar axis, zd, connecting the electron spin density centers of %@mt;sys@%P%@sx@%700%@be@%•+%@sxx@%%@mx@% and %@mt;sys@%A%@sx@%1%@be@%•-%@sxx@%%@mx@% . A partially resolved hyperfine coupling (hfc) is assigned to the hfc tensor of the 2-methyl group of A1. Its A∥ principal axis encloses an angle of β = 35°−55° with c. Simulations of the rotation patterns support a lower limit for the angle ∠(c, zd) ≥ 25° with a larger error than for the upper limit. zd is confirmed to be parallel to both the gxx principal axis of g(%@mt;sys@%A%@sx@%1%@be@%•-%@sxx@%%@mx@% ) and to the C&dbd;O carbonyl bonds within ±5°. With respect to rotation around the gxx axis, the angle between the (c, zd) plane and the quinone plane of the %@mt;sys@%A%@sx@%1%@be@%•-%@sxx@%%@mx@% head group can only be specified within an upper limit of 60°. Together with independent knowledge about the location of A1 within the PSI reaction center, a nearly complete structural model for the head group of the functional A1 cofactor is achieved.

Copyright of Acta Endoscopica is the property of Lavoisier and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Endoscopica is the property of Lavoisier and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Endoscopica is the property of Lavoisier and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Endoscopica is the property of Lavoisier and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Ohne Zusammenfassung:

Electrons produced by Chl-aIIin a short flash are finally transfered to Chl-ai after having passed several intermediates. The reaction between Chl-aIand its primary electron donators PD (probably Cyt-f and PC) has been studied by means of high time resolution flash photometry in isolated spinach chloroplasts with the following results:

New absorption changes with a life time of 2·10—4sec at ∼690 nm probably represent the chlorophyll-a light reaction in photosynthesis which promotes the cleavage of water.

1. The Chl-b reaction in chloroplasts is biphasic.

After the reduction of PQ in the light, PQ=is oxidized in the dark. Three types of reoxydation can be distinguished in isolated chloroplasts of spinach:

Plastoquinone PQ is engaged in photosynthesis 1. Difference spectra in the UV-region indicate that PQ is an intermediate in the electron transport chain 2. PQ is located as a pool between the two light reactions I and II 3. PQ is reduced by hνIIand oxidized by hνI3. In this paper the difference spectra which occur during light excitation of spinach chloroplasts and chlorella vulgaris were measured in the UV-region with high resolution by the high sensitive method of periodical flash photometry 6.

Monomer free polystyrene samples, produced by evaporation from a solvent excluding oxygen, show by excitation with UV-light (λ=270 nm) or with β-rays besides the excimer peak at 330 nm (P-peak) an additional fluorescence peak at 390 nm (G-peak). This peak disappears by melting of the sample or admission of air. The influence of additives on the fluorescence spectra was investigated. 1,2-di-(2-pyridyl)-ethylene, an efficient quencner for the first excited singlet state of polystyrene, reduces the P-peak much more than the G-peak. Therefore it is inprobable that the states responsible for the P-and G-peak are excimers of different distance or symmetry of the segmers or excimers with more than 2 segmers participating. The intensity of the G-peak in comparison to the P-peak increases by addition of low concentrations of hexachlorocyclohexane (c<10-5 mole/1). The dependence on the structure of the polymer and the influence of the electron scavenger suggests, that the appearance of the G-peak is connected with the existence of electron traps. We assume that the origin of the G-peak is a charge separate state analogous to that proposed by Janssen and Funabashi to explain the luminescence in γ-irradiated alkane glasses.

In order to test recent interpretations of field indicating absorption changes in photosynthesis, the influence of the electric field on the absorption spectrum of chlorophyll-b is measured in vitro.

A repetitive laser giant pulse photometer is described which can resolve absorption changes of 0.1% in the time range of 10 ns. With this instrument the following results have been obtained.

A repetitive ultra-short-flash photometer is described which can resolve absorption changes of 0,01% in the time range of 10-7sec. With this instrument the following results have been obtained.

1. Fluorescence changes of umbelliferone have been used as indicator for pH changes in the outer phase of the functional membrane of photosynthesis. In combination with the repetitive pulse technique it is possible to measure the pH change which is produced during one turn-over of the molecular machinery (Δ pH ≈ 10−4). The analysis of this primary pH changes gives insight in the primary ionic events in general.

Electrical field changes across the function membrane of photosynthesis have been measured via special absorption changes. These occur by the action of the field on pigments which are located within the membrane. - Proton translocation has been measured by absorption changes of added pH indicators. Repetitive flash technique has been used for the sensitive detection of these absorption changes.

1. The complete difference spectrum of the reaction of the photoactive chlorophyll-an is presented.

From action spectra of separated light reactions the function of different chlorophylls in photosynthesis have been estimated.

In salzartigen Nitriden und Carbiden werden geringe Oxydgehalte durch Lösen der Präparate in wasserfreiem Methanol + wasserfreier Essigsäure und anschließende Mikrotitration des gebildeten Wassers mit Karl-Fischer-Reagens direkt bestimmt. Die Titration wird bei 0° C durchgeführt, um eine störende Veresterung von Essigsäure und Alkohol zu vermeiden.

Ohne Zusammenfassung: