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M Baldus

Publications and source records attributed to M Baldus.

At least 19 recordsLinked to original sources
PubMed2004

Probing membrane protein orientation and structure using fast magic-angle-spinning solid-state NMR.

One and two-dimensional solid-state NMR experiments are discussed that permit probing local structure and overall molecular conformation of membrane-embedded polypeptides under Magic Angle Spinning. The functional dependence of a series of anisotropic recoupling schemes is analyzed using theoretical and numerical methods. These studies lead to the construction of a set of polarization dephasing or transfer units that probe local backbone conformation and overall molecular orientation within the same NMR experiment. Experimental results are shown for a randomly oriented peptide and for two model membrane-peptides reconstituted into lipid bilayers and oriented on polymer films according to a method proposed by Bechinger et al.

Anisotropy↗
PubMed2001

Detection of Aspergillus species in blood and bronchoalveolar lavage samples from immunocompromised patients by means of 2-step polymerase chain reaction: clinical results.

Bronchoalveolar lavage (BAL) samples from 67 patients who were at high risk for invasive aspergillosis were examined using a recently developed 2-step polymerase chain reaction (PCR) that detects </=10 fg of Aspergillus DNA in blood and BAL samples in vitro. Thirteen of these patients had PCR and diagnostic results positive for Aspergillus infection. Four patients with possible invasive aspergillosis also had positive PCR results, and the remaining 50 had negative PCR results. In addition, 907 blood samples from 218 high-risk patients were screened. Thirty-three patients with positive PCR results had invasive aspergillosis; 148 patients had PCR and diagnostic results that were negative, and 34 patients with positive PCR results had nonconclusive clinical data. Both blood and BAL testing were performed for 45 patients. All 8 patients with proven invasive aspergillosis showed concordance of positive PCR results. Our data suggest that this PCR method has possible clinical value for confirming and improving the diagnosis of invasive aspergillosis in high-risk patients.

Adolescent↗
PubMed2001

Ultrahigh field MAS NMR dipolar correlation spectroscopy of the histidine residues in light-harvesting complex II from photosynthetic bacteria reveals partial internal charge transfer in the B850/His complex.

Low-temperature 15N and 13C CP/MAS (cross-polarization/magic angle spinning) NMR has been used to analyze BChl-histidine interactions and the electronic structure of histidine residues in the light-harvesting complex II (LH2) of Rhodopseudomonas acidophila. The histidines were selectively labeled at both or one of the two nitrogen sites of the imidazole ring. The resonances of histidine nitrogens that are interacting with B850 BChl a have been assigned. Specific 15N labeling confirmed that it is the tau-nitrogen of histidines which is ligated to Mg2+ of B850 BChl molecules (beta-His30, alpha-His31). The pi-nitrogens of these Mg2+-bound histidines were found to be protonated and may be involved in hydrogen bond interactions. Comparison of the 2-D MAS NMR homonuclear (13C-13C) dipolar correlation spectrum of [13C6,15N3]-histidines in the LH2 complex with model systems in the solid state reveals two different classes of electronic structures from the histidines in the LH2. In terms of the 13C isotropic shifts, one corresponds to the neutral form of histidine and the other resembles a positively charged histidine species. 15N-13C double-CP/MAS NMR data provide evidence that the electronic structure of the histidines in the neutral BChl a/His complexes resembles the positive charge character form. While the Mg...15N isotropic shift confirms a partial positive charge transfer, its anisotropy is essentially of the lone pair type. This provides evidence that the hybridization structure corresponding to the neutral form of the imidazole is capable of "buffering" a significant amount of positive charge.

Culture Media↗
PubMed2001

Backbone and side-chain 13C and 15N signal assignments of the alpha-spectrin SH3 domain by magic angle spinning solid-state NMR at 17.6 Tesla.

The backbone and side-chain 13C and 15N signals of a solid 62-residue (u-13C,15N)-labelled protein containing the alpha-spectrin SH3 domain were assigned by two-dimensional (2D) magic angle spinning (MAS) 15N-13C and 13C-13C dipolar correlation spectroscopy at 17.6 T. The side-chain signal sets of the individual amino acids were identified by 2D 13C-13C proton-driven spin diffusion and dipolar recoupling experiments. Correlations to the respective backbone nitrogen signals were established by 2D NCACX (CX=any carbon atom) experiments, which contain a proton-nitrogen and a nitrogen-carbon cross-polarisation step followed by a carbon-carbon homonuclear transfer unit. Interresidue correlations leading to sequence-specific assignments were obtained from 2D NCOCX experiments. The assignment is nearly complete for the SH3 domain residues 7-61, while the signals of the N- and C-terminal residues 1-6 and 62, respectively, outside the domain boundaries are not detected in our MAS spectra. The resolution observed in these spectra raises expectations that receptor-bound protein ligands and slightly larger proteins (up to 20 kDa) can be readily assigned in the near future by using three-dimensional versions of the applied or analogous techniques.

Amino Acid Sequence↗
PubMed2001

Heteronuclear 2D-correlations in a uniformly [13C, 15N] labeled membrane-protein complex at ultra-high magnetic fields.

One- and two-dimensional solid-state NMR experiments on a uniformly labeled intrinsic membrane-protein complex at ultra-high magnetic fields are presented. Two-dimensional backbone and side-chain correlations for a [U-13C, 15N] labeled version of the LH2 light-harvesting complex indicate significant resolution at low temperatures and under Magic Angle Spinning. Tentative assignments of some of the observed correlations are presented and attributed to the alpha-helical segments of the protein, mostly found in the membrane interior.

Amino Acid Sequence↗
PubMed2001

Secondary chemical shifts in immobilized peptides and proteins: a qualitative basis for structure refinement under magic angle spinning.

Resonance assignments recently obtained on immobilized polypeptides and a membrane protein aggregate under Magic Angle Spinning are compared to random coil values in the liquid state. The resulting chemical shift differences (secondary chemical shifts) are evaluated in light of the backbone torsion angle psi previously reported using X-ray crystallography. In all cases, a remarkable correlation is found suggesting that the concept of secondary chemical shifts, well established in the liquid state, can be of similar importance in the context of multiple-labelled polypeptides studied under MAS conditions.

Carbon↗
PubMed2000

Multiple-quantum cross polarization in quadrupolar spin systems during magic-angle spinning.

We describe the concept of multiple-quantum cross polarization (CP) between an I = 32 and an I = 12 spin during magic-angle spinning. Experimental and theoretical results for (23)Na-(1)H pairs are presented that elucidate the transfer mechanism and the beneficial effect of adiabatic amplitude modulations of the CP field. The multiple-quantum CP approach is shown to be beneficial for improving the sensitivity of CP-MQMAS experiments and for detecting dipolar correlations.

Magnetic Resonance Spectroscopy↗
PubMed2000

CD34+ cell enrichment for autologous peripheral blood stem cell transplantation by use of the CliniMACs device.

Several devices for selection of CD34+ peripheral blood stem cells (PBSC) have been used during the last years for reducing tumor cell contamination of the graft. The new CliniMACS system (magnetic-activated cell separation system by Miltenyi Biotech GmbH, Bergisch-Gladbach, Germany) was recently approved for clinical use in Europe. To evaluate its purging efficiency and engraftment data in the autologous transplant, PBSC from 28 adult patients with various malignant diseases (non-Hodgkin's lymphoma, n = 17; chronic lymphocytic leukemia, n = 5; multiple myeloma, n = 4; acute lymphocytic leukemia, n = 1; medulloblastoma, n = 1) were mobilized by chemotherapy and granulocyte colony-stimulating factor (G-CSF) (10 microg/kg per day). Thirty leukapheresis products from 28 patients with a median of 4.4 x 10(8) nucleated cells/kg body weight (bw)(range 0.6-10.8 x 10(8)/kg bw) and a median of 7.1 x 10(6) CD34+ cells/kg bw (range 2.8 to 18.8 x 10(6)/kg bw) were selected using the Cobe spectra cell separator (Cobe BCT Inc., Lakewood, CO). After the CliniMACS procedure, the median yield of CD34+ selected cells was 4.5 x 10(6)/kg (range 2.2-11.1 X 10(6)/kg bw) with a median recovery of 69.5% (range 46.9-87.3%) and a median purity of 97.7% (range 89.4-99.8%). The procedure did not alter viability of selected cells, which was tested by propidium iodide staining. So far, purified PBSC were used for autologous transplantation in 15 out of 28 patients after total body irradiation and/or high-dose chemotherapy. Median time to reach an absolute neutrophil count > 500/microl was 12 days (range 10-18 days), platelet recovery >50,000/microl occurred at day + 16 (range 11-22). With a median follow-up time of 12 months (range 3-19), 5 patients died of relapse. We confirmed the feasibility and safety of the CliniMACS CD34+ cell enrichment procedure in adult patients with autologous PBSC transplantation.

Adult↗
PubMed1999

Chédiak-Higashi-Steinbrinck syndrome (CHS) in a 27-year-old woman--effects of G-CSF treatment.

Chédiak-Higashi-Steinbrinck syndrome (CHS) is a rare autosomal recessive disorder which is usually lethal in early childhood. Diagnostic hallmark is the occurrence of giant inclusion bodies in peripheral leukocytes and their bone marrow precursors. We report on a 27-year-old female patient who was admitted for treatment of a skin abscess. She recovered after intravenous antibiotic treatment and surgical incision. Hematological investigation was initiated because of a persisting neutropenia of 15%, with a leukocyte count initially in the normal range but subsequent leukopenia. Case history revealed recurrent skin infections from childhood on, regularly requiring surgical intervention. One year prior to admission a neuropathy had been diagnosed, while a partial albinism had been known for years. Microscopic examinations of peripheral blood and bone marrow aspirate smears were diagnostic for CHS. Additionally, a secondary antibody deficiency was found. Normalization of the white blood cell count, including the differential count, was observed following initiation of G-CSF treatment. Functional assessment of phagocytosis and oxidative burst activity of granulocytes revealed normal results before and after stimulation with G-CSF, however, natural killer cell activity was only weak, with slight improvement after G-CSF treatment in vivo. Cytogenetic analysis showed a normal female karyotype. Although the haploidentical brother of the patient may serve as an allogeneic stem cell donor, transplantation has been postponed because of further deterioration of her already existing CHS-specific neurological impairment. Nevertheless, while receiving G-CSF maintenance treatment our patient experienced no further infectious episodes within 6 months after diagnosis of CHS.

Adult↗
PubMed1999

Biomolecular NMR: recent advances in liquids, solids and screening.

The past year has witnessed significant advances in NMR analysis of bio-macromolecules from a broad array of disciplines. First, great progress in the development of methods for measuring residual dipolar couplings in nematic media promises to increase both the size of systems to be studied and the accuracy with which structures can be determined. Second, the ability of solid-state NMR to provide structural information on biological systems is undergoing rapid expansion as a result of recent developments. The structural details that can be derived for biomolecules in the liquid and solid states can be used for the rational design of high-affinity ligands. Such studies are now complemented by NMR screening of synthetic and natural molecular libraries. Several NMR screening protocols have been designed that employ both rational and random elements.

Animals↗
PubMed1998

Broadband dipolar recoupling in rotating solids: a numerical comparison of some pulse schemes.

A numerical comparison of the dipolar recoupling performance of several previously published homonuclear recoupling schemes under magic angle-spinning conditions is presented. Emphasis is put on the recoupled polarization transfer in a two-spin system where the efficiency is studied as a function of resonance offsets in the presence and absence of chemical-shielding anisotropies. In addition, the effect of the rf field strength is investigated. Powder pattern line shapes are shown in the on-resonance case that reveal the distribution of dipolar couplings for each recoupling scheme. These results are compared to data computed with a purposely misset rf field strength to estimate the pulse scheme sensitivity to rf-inhomogeneity and experimental missettings.

Computer Simulation↗
PubMed1998

Correlation of cytogenetic, molecular cytogenetic, and clinical findings in 59 patients with ANLL or MDS and abnormalities of the short arm of chromosome 12.

Abnormalities of the short arm of chromosome 12 (12p) are found in about 5% of acute nonlymphocytic leukaemias (ANLL) and myelodysplastic syndromes (MDS). They are described to be characteristic of secondary leukaemias, especially after prior mutagenic exposure, and to be associated with a poor prognosis. In our series of 59 patients with 12p abnormalities and ANLL or MDS, exposure to genotoxic agents was proven only in five patients, but in 13/44 patients ANLL evolved from an MDS. Patients with a small deletion del(12)(p11.2p13) having a mild clinical course were distinguished from those with a large del(12)(p11.2), additional chromosomal anomalies, and a poor clinical course. Among the 31 patients with translocations or dicentric chromosomes involving 12p, a group of eight with t/dic(12;13) was the most frequent and was associated with a poor prognosis. The clinical outcome was adverse in the majority of patients with complex karyotype abnormalities, but in some patients a milder clinical course seems likely. A new, hitherto undescribed, abnormality in an MDS case with a duplication dup(12)(p11.2p13) was the amplification of the signal of the yeast artificial chromosome (YAC) clone 964c10 (D12S736). In 38 cases with deletions or unbalanced translocations/dicentrics one YAC signal was lost. Five patients with balanced translocations demonstrated breakpoints within the YAC, containing the ETV6 (TEL) gene. The breakpoints were telomeric to the YAC 964c10 in seven cases and centromeric in one patient.

Adult↗
PubMed1998

Transferrin receptor assay and zinc protoporphyrin as markers of iron-deficient erythropoiesis in end-stage renal disease patients.

To evaluate storage iron deficiency and iron-deficient erythropoiesis we determined, in a cross-sectional study of 95 patients mainly including end-stage renal disease patients (ESRD) with (32) and without rh-EPO therapy (55), the following parameters: hemoglobin, mean corpuscular red cell volume, ferritin, transferrin saturation (TS), zinc protoporphyrin (ZPP) and soluble transferrin receptor (TfR). In the dialysis group the percentage of positive samples with each marker of tissue iron supply defined as TS < 20%, ZPP > 40 mumol/mol Heme and TfR > 3.05 microgram/ml was as follows: TS 43.7% and 32.2% at a diagnostic threshold level of < 16%, ZPP 33.3% and TfR 17.2%. Manifest storage iron deficiency defined as ferritin < 30 ng/ml was observed in 5.7% of the samples while the mean ferritin concentration of the rh-Epo treated dialysis patients was 509.3 ng/ml compared to 262.5 ng/ml in the group without rh-EPO therapy. These data reflect a generous iron substitution in our series taking a TS < 20% as an intervention criterion. Looking at the different results of the three markers the best correspondence was found between ZPP and TfR resulting in a weak positive correlation (+0.64). In conclusion, we found quite different results with different assays when evaluating endogenous iron availability in our series of mainly ESRD patients in a cross-sectional study. Because a gold-standard is not defined further firm conclusions cannot be drawn from this type of study. The adequacy of the different parameters of iron metabolism including threshold levels and, consequently, the decision and route of iron substitution deserve an evaluation in a longitudinal study to characterize the best marker or marker combination in this setting.

Adult↗
PubMed1996

Experience with zinc protoporphyrin as a marker of endogenous iron availability in chronic haemodialysis patients.

BACKGROUND: Ferritin and the percentage of transferrin saturation (TS) are established parameters with which to evaluate endogenous iron availability during treatment of renal anaemia with recombinant human erythropoietin (rHuEpo). Zinc protoporphyrin (ZPP) has been proposed as another valid marker in this setting. METHODS: We determined the following parameters in 127 patients, including 117 haemodialysis patients: haemoglobin, erythrocytes, haematocrit, mean corpuscular volume (MCV), iron, ferritin, transferrin saturation and ZPP. Of the patients treated in a cross-sectional study, 38.5% were treated with rHuEpo; 30.7% with intravenous iron; and 13.6% with intravenous iron and rHuEpo simultaneously. Median ferritin was 304 ng/ml and median transferrin saturation was 21.2%. RESULTS: Including cases with manifest storage iron deficiency, a concordant elevated ZPP ( > 40 mumol/mol haem) and a decreased transferrin saturation ( < 20%) were found in 23 of our dialysis patients (19.6%) while 55 cases (47%) were classified as concordantly negative. However, as many as 39 cases (33.3%) showed discrepant results: in 16 cases (13.6%) ZPP was elevated but transferrin saturation was in the normal range, while in 23 cases (19.6%) the opposite results were observed. CONCLUSIONS: We conclude that beyond the border of manifest storage iron deficiency, defined as a ferritin < 30 ng/ml in male and < 15 ng/ml in female patients, ZPP and TS cover different ranges of functional iron deficiency which is reflected in the lack of a correlation of ZPP to any other of the above-mentioned parameters. Our data suggest that a TS < 20% as a diagnostic, and thus intervention, criterion in the evaluation of functional iron deficiency and iron substitution beyond manifest storage iron deficiency might result in overestimation of iron requirements. It remains to be shown in a longitudinal study, also reflecting the course of haemoglobin and the mean rHuEpo dose, whether ZPP or TS is the more appropriate parameter in the evaluation of functional iron availability.

Adult↗
PubMed1994

A case of pure red cell aplasia: follow-up on different immunosuppressive regimens.

A 66-year-old patient was admitted to our hospital in January 1992 for further evaluation of severe normocytic anemia. Hemoglobin (Hb) was 3.5 g/dl, reticulocyte count 1%. Bone marrow showed a nearly complete lack of red cell precursors, thus favoring the diagnosis of acquired pure red cell aplasia (PRCA). Immunosuppressive therapy with prednisolone was started but had to be supplemented with azathioprine because of a further rapid decrease in Hb to 3.7 g/dl after an initial transfusion of 6 U red blood cells. However, with this regimen a renewed decrease in Hb to 6.6 g/dl was noted, and further transfusions were required. Therefore therapy was switched to cyclosporine A (CyA) while tapering off prednisolone. Four months after the initial diagnosis a positive parvovirus B19 IgM antibody was found. After the failure of hematological remission with three immunosuppressive regimens a course of high-dose intravenous immunoglobulins (IVIG) was administered in July 1992. Six weeks after IVIG therapy a peak hemoglobin concentration of 12.3 g/dl was noted, and further transfusion was not required. CyA was tapered off in October 1992. One month later CyA was reinstituted because of a relapse of PRCA but was unsuccessful until January 1993. At this time immunosuppressive CyA therapy was discontinued because of a periodontal abscess. In February 1993 a second IVIG infusion was given, and a second remission of PRCA was noted, showing an increase in hemoglobin up to 14.5 g/dl by November 1993. At the last follow-up visit in February 1994 our patient was still in complete hematological remission.

Aged↗
PubMed1994

Detection of primary HIV infection by a second-generation HIV(p24) antigen test.

We studied the course of a primary HIV infection in a 54-year-old woman. Probably the source of infection was sexual intercourse, since other risks, such as i.v. drug use, acupuncture and transfusion were excluded. On admission she presented with fever, a maculopapular rash, and moderate enlargement of nuchal lymph nodes. At that time the anti-HIV 1,2 enzyme immunoassay was negative. However, the HIV-p24 Ag test, which was performed in every HIV screening in our laboratory, was positive. The suspicion of an acute HIV infection was supported by a positive HIV-cDNA-PCR and confirmed by Western blot after seroconversion. As additional finding, the blood smear showed abnormal white cell differential count, indicating viral infection. Aminotransferases were slightly increased, and antibodies to hepatitis B surface and core antigens demonstrated former hepatitis B infection. It is concluded that in this case the HIV-p24 Ag test proved its suitability for early diagnosis of an acute HIV infection. In case of testing blood donors, none of the compulsory serological screening methods would have detected the HIV infection.

AIDS Serodiagnosis↗