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G Rapp

Publications and source records attributed to G Rapp.

54 records · Page 3Linked to original sources
PubMed1991

Time-resolved X-ray diffraction study of structural changes associated with the photocycle of bacteriorhodopsin.

The time course of structural changes accompanying the transition from the M412 intermediate to the BR568 ground state in the photocycle of bacteriorhodopsin (BR) from Halobacterium halobium was studied at room temperature with a time resolution of 15 ms using synchrotron radiation X-ray diffraction. The M412 decay rate was slowed down by employing mutated BR Asp96Asn in purple membranes at two different pH-values. The observed light-induced intensity changes of in-plane X-ray reflections were fully reversible. For the mutated BR at neutral pH the kinetics of the structural alterations (tau 1/2 = 125 ms) were very similar to those of the optical changes characterizing the M412 decay, whereas at pH 9.6 the structural relaxation (tau 1/2 = 3 s) slightly lagged behind the absorbance changes at 410 nm. The overall X-ray intensity change between the M412 intermediate and the ground state was about 9% for the different samples investigated and is associated with electron density changes close to helix G, B and E. Similar changes (tau 1/2 = 1.3-3.6 s), which also confirm earlier neutron scattering results on the BR568 and M412 intermediates trapped at -180 degrees C, were observed with wild type BR retarded by 2 M guanidine hydrochloride (pH 9.4). The results unequivocally prove that the tertiary structure of BR changes during the photocycle.

Bacteriorhodopsins↗
PubMed1991

Time-resolved X-ray diffraction studies on stretch-activated insect flight muscle.

The specific feature of stretch activation of the indirect flight muscle of the tropical waterbug Lethocerus was used to correlate mechanical and structural aspects of muscle contraction. The time courses of the changes in intensities of the strongest equatorial reflections, the (10) and (20) and of the first meridional reflection at 14.5 nm-1 were monitored using synchrotron radiation as a high intensity X-ray source. The ratio of the intensities of the equatorial reflections, (I20/I10), which reflects the mass distribution within the filament lattice array, increases by about 10% relative to the Ca(2+)-activated level when a rapid stretch is imposed, compared with a 200% change seen when fibres change from the relaxed to the rigor state, while the spacing of the lattice planes decreases by about 1%. The intensity of the first meridional reflection at 14.5 nm-1 decreases by about 35% during stretch activation with a slightly faster time course than the delayed tension increase. The results suggest that the average structure of cycling crossbridges is different from that present in the rigor state.

Actin Cytoskeleton↗
PubMed1991

Dynamic X-ray diffraction measurements following photolytic relaxation and activation of skinned rabbit psoas fibres.

1) The ATP binding and crossbridge dissociation in muscle fibres is as fast as in solution, has a Q10 ca. 2-3, and is not measurably strain sensitive. 2) The final ADP release from the AM.ADP state achieved by adding ADP to rigor fibres must be greater than or equal to 69 sec-1 at 10 degrees C, and the combination of this rate and the ADP rebinding rate at 1 mM ADP limits the ATP induced crossbridge dissociation rate at greater than 2 mM ATP, but these kinetics were not strain sensitive. The strain sensitive steps must occur earlier on the attached pathway. 3) On activation, the equatorial changes thought to reflect crossbridge attachment are faster than tension production. The 10 intensity may change slightly ahead of the 11. This rate was not very temperature sensitive unlike the tension producing step in the mechanism. 4) The re-equilibration of equatorial intensity levels was much faster on activation from the rigor state than from the relaxed state. We conclude that crossbridges do not necessarily move far from the thin filaments when they detach in a fully activated thin filament system. 5) The 14.3 nm meridional intensity increases greater than 200% on fibre activation at 24 degrees C. The structural reorganisation of the heads responsible for this increase is associated with the tension generating step in the ATPase mechanism rather than the initial binding of bridges.

Adenosine Diphosphate↗
PubMed1991

Luque interpeduncular segmental fixation of the lumbosacral spine.

Interpeduncular segmental fixation of the lumbar and lumbosacral spine with Luque screws and plates is becoming increasingly popular. In this retrospective study, 52 consecutive patients treated with this technique were followed for 16 to 44 months (average, 21). Indications for surgical arthrodesis included lumbar instability from degenerative disease (16 cases), spondylolisthesis (25 cases), pseudarthrosis (eight cases), fracture (two cases), and tumor (one case). Fusion with instrumentation spanned one level in nine patients, two in 38 patients, three in four patients, and four in one patient. Patients wore a rigid lumbar orthosis for an average of six months (range, two to 16). Ten complications occurred in nine patients: two superficial wound infections, four neurologic complications, three loosened screws, and one broken screw. An overall fusion rate of 96% was achieved; pseudarthrosis is suspected in one case and failed arthrodesis secondary to trauma in a second patient. At four months postoperatively, solid unions had resulted in most of the cases, as seen roentgenographically. All patients reported decreased back pain; however, one patient is addicted to narcotics. Twenty-five of the 29 patients employed were able to return to work at an average of six months postoperatively.

Adolescent↗
PubMed1990

Time-resolved X-ray crystallographic study of the conformational change in Ha-Ras p21 protein on GTP hydrolysis.

Crystals of Ha-Ras p21 with caged GTP at the active site have been used to investigate the conformational changes of p21 on GTP hydrolysis. The structure of the short-lived p21.GTP complex was determined by Laue diffraction methods. After GTP hydrolysis, substantial structural changes occur in the parts of the molecule implicated in the interaction with GTPase-activating protein. The trigger for this process seems to be a change in coordination of the active-site Mg2+ ion as a result of loss of the gamma-phosphate of GTP.

Binding Sites↗
PubMed1990

Characterization of three abundant mRNAs from human ovarian granulosa cells.

Three cDNA clones, pHGR122, pHGR11, and pHGR74 containing the coding information for abundant mRNAs were identified from a human ovarian granulosa cell cDNA library. Characterization by nucleotide sequencing revealed that pHGR122 was specific for a collagenase inhibitor and pHGR11 for melanoma-associated antigen ME491. Relative quantification by Northern analysis indicated that collagenase inhibitor mRNA is a major species in granulosa cells. This finding provides evidence for the origin of this protein in follicular fluid as a secretory product of granulosa cells. pHGR11 identified melanoma-associated antigen ME491 as the unexpected product of normal, noncarcinogenic, granulosa cells. pHGR74 has the complete coding information for an unknown protein. Three independent experiments: (i) cell-free translation of pHGR74 RNA; (ii) transcription of suitable restriction fragments followed by cell-free translation; (iii) hydrolysis of the cell-free translation product of pHGR74 RNA by endoproteinase Lys-C, identified one open reading frame coding for an acidic, highly hydrophilic protein of 111 amino acid residues. pHGR74 mRNA is expressed in human testis, prostate, seminal vesicle, and ovarian granulosa cells. A comparative Southern analysis indicates pHGR74 mRNA is species specific and encoded by a single-copy gene.

Amino Acid Sequence↗
PubMed1989

Biochemical and crystallographic characterization of a complex of c-Ha-ras p21 and caged GTP with flash photolysis.

The GTP binding domain of the c-Ha-ras protooncogene product (p21'c) and the corresponding region from an oncogenic mutant form of the protein in which glycine at position 12 has been replaced by valine [p21'(G12V)] have been crystallized with P3-1-(2-nitro)phenylethylguanosine 5'-O-triphosphate (caged GTP) at their active sites. The crystals give x-ray diffraction patterns to a resolution of better than 0.3 nm. Photolysis can be achieved in the crystal, after which GTP hydrolysis takes place at the rate expected from solution studies. Complete x-ray data sets have been obtained for the starting caged-GTP state and the final GDP state after photolysis and hydrolysis, demonstrating the feasibility of time-resolved structural investigations of the process of GTP hydrolysis.

Binding Sites↗
PubMed1989

Complete sequence of the coding region of human elongation factor 2 (EF-2) by enzymatic amplification of cDNA from human ovarian granulosa cells.

The use of two primers allowed the specific enzymatic amplification of elongation factor 2 starting with total double-stranded cDNA from human ovarian granulosa cells. The amplified DNA fragment with a length of 1765 bp was restricted and sequenced by the shot gun approach. From the sequences obtained from the amplified fragment and the cDNA insert of pHGR81 [Rapp et al. (1988) Biol. Chem. Hoppe-Seyler 369, 247-250] respectively, the DNA sequence containing the complete coding as well as the 3'-untranslated region was assembled.

Animals↗
PubMed1988

A low cost high intensity flash device for photolysis experiments.

Novel techniques of flash photolysis experiments require high intensity light sources in the near UV. We describe here a simple and inexpensive flash device which may complete with bulky and expensive laser systems if the experiments do not necessitate very short light pulses. Using a particular optical arrangement and stored electrical energy, a variation of the parameters voltage and capacitance led to a difference in light output by a factor of more than two. The system is used to relax both skeletal and smooth muscle fibres in the rigor state by releasing up to 2 mM ATP from 12.5 mM caged-ATP.

Adenosine Triphosphate↗
PubMed1988

Cloning and sequence analysis of a cDNA from human ovarian granulosa cells encoding the C-terminal part of human elongation factor 2.

A cDNA clone, pHGR81, encoding 358 amino-acid residues of the C-terminal region of human elongation factor 2 (EF-2), was isolated from a human ovarian granulosa cell cDNA library. The deduced amino-acid sequence of pHGR81, when compared with the known identical amino-acid sequences of hamster as well as rat EF-2 revealed a substitution of a glutamine by an alanine residue in the partially determined human sequence. The 15 amino-acid-residue sequence comprising the histidine-715, supposed to be of importance for the biological function of EF-2, is preserved in human EF-2. The coding region of the cDNA insert of pHGR81 displays a homology of 87% to hamster and of 88% to rat EF-2 cDNA. In Northern-transfer analysis, pHGR81 specifically hybridizes with an mRNA species of 3.1 kb.

Amino Acid Sequence↗
PubMed1988

The time course of changes in the equatorial diffraction patterns from different muscle types on photolysis of caged-ATP.

Using the synchrotron X-ray source at DESY, Hamburg, we have measured the time courses of changes in the strongest equatorial reflections from small bundles of chemically skinned fibres from insect flight muscle, Limulus muscle and rabbit psoas and soleus muscles following the photolytic release of ATP. In all preparations the release of ca. 2 mM ATP caused the tension to relax with a complex time course, the final relaxation rates in insect and rabbit psoas fibres being ca. 10 times faster than those measured in rabbit soleus and Limulus fibres (ca. 50 ms cf. ca. 500 ms half times). However, in all fibre types there was a very rapid change in equatorial intensities towards relaxed values (half time less than 5 ms), the extent of this change and the occurrence of a slower phase of intensity change being dependent on the preparation. In insect the 1.0 and 2.0 intensities change rapidly to their relaxed values; in Limulus the 1.0 and 1.1 intensities change rapidly to within ca. 10% of their relaxed values; in rabbit psoas the initial, rapid 1.1 intensity fall is to within 30-40% of its relaxed value and is followed by a slower fall which appears to correlate with the rate of the final tension relaxation, e.g. phosphate ions accelerate both rates; in rabbit soleus the equatorial response is very similar to that of psoas fibres. These results are discussed in terms of the model of Goldman et al. in which a rapid ATP induced dissociation of rigor crossbridges is followed by the transient cooperative reattachment of some bridges which may proceed through at least part of the cross-bridge cycle.

Actomyosin↗
PubMed1987

Relaxation of chemically skinned guinea pig taenia coli smooth muscle from rigor by photolytic release of adenosine-5'-triphosphate.

The mechanical events following release of ATP from P3-1-(2-nitro)phenylethyladenosine-5'-triphosphate (caged-ATP) in skinned guinea pig taenia coli smooth muscle in rigor were investigated. A rigor force of about 25-35% of the maximal active force was obtained by removing ATP at the plateau of a maximal active contraction. In the rigor solution free-Mg2+ was 2 mM, ionic strength 90 mM and pH 7.0. When caged-ATP (12.5 mM) was diffused into the preparation there was no change in the rigor force. Photolytic production of about 2 mM ATP was achieved with a xenon flash lamp. Following illumination, force decreased with an approximate initial rate constant of 0.7 s-1. The rate of relaxation was increased in the presence of inorganic phosphate (at 3 mM: 1.3 s-1; 10 mM: 2.2 s-1). At higher Mg2+ concentrations the rate of relaxation was slower (5 mM: 0.2 s-1) and at lower concentrations the rate was faster (0.5 mM: 1.2 s-1). An increased rate of relaxation was observed when ionic strength was increased to 150 mM (2.2 s-1). Phosphate increased the rate of relaxation at the different levels of Mg2+ (0.5-10 mM) and ionic strength (90, 150 mM). In preparations shortened (by 1-3%) to give reduced rigor force, a small transient increase in tension was recorded after ATP release. In comparison to the rates of ATP-induced dissociation of actomyosin in solution, reported in the literature, the rate of relaxation from rigor is slower. This may reflect a slow rigor cross-bridge dissociation or mechanical interactions not associated with cross-bridges in the muscle fibre.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1986

Prenatal diagnosis of a congenital mesoblastic nephroma. A case report.

Fetal urinary tract malformations are diagnosed frequently with ultrasonography. There are many published papers on in utero detection of fetal cystic abnormalities. In this case the prenatal diagnosis of a solid kidney mass was made, and histopathologic examination after surgical resection revealed congenital mesoblastic nephroma.

Adult↗
PubMed1985

Lead in bone III. Prediction of social correlates from skeletal lead content in four Colonial American populations (Catoctin Furnace, College Landing, Governor's Land, and Irene Mound).

Lead content was determined in the skeletal tissue of 82 individuals representing two black and two white Colonial American populations: Catoctin Furnace, College Landing, Governor's Land, and Irene Mound. Group and individual differences in bone lead concentrations were used to assess behavioral, social and occupational characteristics. Variations in skeletal lead content suggested that the white owners of the Catoctin iron furnace shared little of their food and beverage with their black, male, industrial slaves, but that some of these workers' women had access to the owners' food sources--probably via domestic duty assignments. A broad range of lead concentrations in bones of the free blacks at College Landing implies a wide range of economic success among these tradesmen. Bone lead content of the white populations at Governor's Land and Irene Mound helped confirm family relationships that had been assigned on an archaeological and osteological basis, and also suggested that the social and functional status of the white tenant farmers' white servants frequently differed little from that of black slaves. These findings suggest that, when applied in appropriate circumstances, lead studies of archaeological skeletal tissue may provide information supplemental to that derived from historical, archaeological, or other conventional sources.

Adolescent↗
PubMed1982

Comparative studies on fast muscle myosin light chains after different training programs.

Fast muscle myosin of guinea pigs exposed to different training programs was examined by means of SDS gel electrophoresis. The percentile distribution of the light chains was calculated. Training at 0.7 m/s and 5 degrees slope 20 min per day for 30 days caused a significant decrease in the DTNB light chains and a significant increase in the A2 light chains compared to the control group. In contrast, training at 0.4 m/s and 45 degrees slope caused a significant increase in the DTNB light chains and a significant decrease in the A2 light chains. These changes can be interpreted as a combination of muscle transformation and a shift of myosin isoenzymes.

Animals↗
PubMed1981

Lead in bone II: skeletal-lead content as an indicator of lifetime lead ingestion and the social correlates in an archaeological population.

Measurements of skeletal-lead content (by atomic absorption spectroscopy) were made for 16 individuals recovered from a Colonial (1670-1730) plantation cemetery in Virginia. Archaeological and historical evidence allowed the identification of two social groups (plantation proprietors and laborers) within this small population, each with vastly different estimated lifetime lead exposure, reflecting different living conditions. Measured bone-lead levels confirmed these differences. The character of plantation social organization proved a more important determinant of skeletal-lead content in the individuals studied than age, sex or race.

Adult↗
PubMedDate not supplied

Lead in bone. IV. Distribution of lead in the human skeleton.

Flameless atomic absorption spectroscopy was used to measure lead concentrations in samples from 5 selected human skeletal sites (tibia, skull, rib, ilium, and vertebra) obtained from 134 hospital autopsies. Lead was distributed unequally among the different bones in distinct patterns that were age-, and to some extent, sex-dependent. To estimate lead concentration of the entire skeleton, all skeletal bones were divided into 5 groups based on their approximate compact/trabecular bone ratios, considering each of our 5 sampled sites to be the prototype for each such group. Regression analysis of the 10 possible bone site pair values at different ages yielded age-related constants. These constants were incorporated into an equation we developed that can be used both to estimate mean skeletal lead concentration (Pb) of the entire body skeleton and also to predict the lead concentration at any of the other 4 bone sites if any 1 of the 5 is measured. Applications of these data to in vivo bone lead measurements are detailed with respect to selection of the site to be measured, estimation of total skeletal lead burden, anticipated variations or error, and dependence of these factors on age and sex of the sampled population.

Adolescent↗