TY - JOUR A1 - Loges, A. A1 - Scholz, G. A1 - Amadeu de Sosa, Nader A1 - Jingjing, S. A1 - Emmerling, Franziska A1 - John, T. A1 - Paulus, B. A1 - Braun, T. T1 - Studies on the local structure of the F/OH site in topaz by magic angle spinning nuclear magnetic resonance and Raman spectroscopy JF - European journal of mineralogy N2 - he mutual influence of F and OH groups in neighboring sites in topaz (Al2SiO4(F,OH)2) was investigated using magic angle spinning nuclear magnetic resonance (MAS NMR) and Raman spectroscopy. The splitting of 19F and 1H NMR signals, as well as the OH Raman band, provides evidence for hydrogen bond formation within the crystal structure. Depending on whether a given OH group has another OH group or fluoride as its neighbor, two different hydrogen bond constellations may form: either OH···O···HO or F···H···O. The proton accepting oxygen was determined to be part of the SiO4 tetrahedron using 29Si MAS NMR. Comparison of the MAS NMR data between an OH-bearing and an OH-free topaz sample confirms that the 19F signal at −130 ppm stems from F− ions that take part in H···F bonds with a distance of ∼ 2.4 Å, whereas the main signal at −135 ppm belongs to fluoride ions with no immediate OH group neighbors. The Raman OH sub-band at 3644 cm−1 stems from OH groups neighboring other OH groups, whereas the sub-band at 3650 cm−1 stems from OH groups with fluoride neighbors, which are affected by H···F bridging. The integrated intensities of these two sub-bands do not conform to the expected ratios based on probabilistic calculations from the total OH concentration. This can be explained by a difference in the polarizability of the OH bond between the different hydrogen bond constellations or partial order or unmixing of F and OH, or a combination of both. This has implications for the quantitative interpretation of Raman data on OH bonds in general and their potential use as a probe for structural (dis-)order. No indication of tetrahedrally coordinated Al was found with 27Al MAS NMR, suggesting that the investigated samples likely have nearly ideal Al/Si ratios, making them potentially useful as high-density electron microprobe reference materials for Al and Si, as well as for F. KW - Topas KW - NMR KW - XRD PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-561863 DO - https://doi.org/10.5194/ejm-34-507-2022 SN - 1617-4011 VL - 34 IS - 5 SP - 507 EP - 521 PB - Copernicus Publications CY - Göttingen AN - OPUS4-56186 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stebbings, R. A1 - Wang, L. A1 - Sutherland, J. A1 - Kammel, M. A1 - Gaigalas, A.K. A1 - John, M. A1 - Roemer, B. A1 - Kuhne, Maren A1 - Schneider, Rudolf A1 - Braun, M. A1 - Engel, A. A1 - Dikshit, D.K. A1 - Abbasi, F. A1 - Marti, G.E. A1 - Sassi, M.P. A1 - Revel, L. A1 - Kim, S.-K. A1 - Baradez, M.-O. A1 - Lekishvili, T. A1 - Marshall, D. A1 - Whitby, L. A1 - Jing, W. A1 - Ost, V. A1 - Vonsky, M. A1 - Neukammer, J. T1 - Quantification of cells with specific phenotypes I: Determination of CD4+ cell count per microliter in reconstituted lyophilized human PBMC prelabeled with anti-CD4 FICT antibody JF - Cytometry / A N2 - A surface-labeled lyophilized lymphocyte (sLL) preparation has been developed using human peripheral blood mononuclear cells prelabeled with a fluorescein isothiocyanate conjugated anti-CD4 monoclonal antibody. The sLL preparation is intended to be used as a reference material for CD4+ cell counting including the development of higher order reference measurement procedures and has been evaluated in the pilot study CCQM-P102. This study was conducted across 16 laboratories from eight countries to assess the ability of participants to quantify the CD4+ cell count of this reference material and to document cross-laboratory variability plus associated measurement uncertainties. Twelve different flow cytometer platforms were evaluated using a standard protocol that included calibration beads used to obtain quantitative measurements of CD4+ T cell counts. There was good overall cross-platform and counting method agreement with a grand mean of the laboratory calculated means of (301.7 ± 4.9) µL-1 CD4+ cells. Excluding outliers, greater than 90% of participant data agreed within ±15%. A major contribution to variation of sLL CD4+ cell counts was tube to tube variation of the calibration beads, amounting to an uncertainty of 3.6%. Variation due to preparative steps equated to an uncertainty of 2.6%. There was no reduction in variability when data files were centrally reanalyzed. Remaining variation was attributed to instrument specific differences. CD4+ cell counts obtained in CCQM-P102 are in excellent agreement and show the robustness of both the measurements and the data analysis and hence the suitability of sLL as a reference material for interlaboratory comparisons and external quality assessment. KW - CD4+ cell counting KW - Relative concentration measurement KW - Lyophilized cells KW - Flow cytometry KW - Standard measurement procedure KW - Measurement of uncertainty KW - Human immunodeficiency virus-1 KW - Acquired immunodeficiency syndrome KW - Reference material PY - 2015 DO - https://doi.org/10.1002/cyto.a.22614 SN - 0196-4763 SN - 1552-4922 SN - 1552-4930 VL - 87 IS - 3 SP - 244 EP - 253 PB - Wiley-Liss CY - Hoboken, NJ AN - OPUS4-32847 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wang, L. A1 - Stebbings, R. A1 - Gaigalas, A.K. A1 - Sutherland, J. A1 - Kammel, M. A1 - John, M. A1 - Roemer, B. A1 - Kuhne, Maren A1 - Schneider, Rudolf A1 - Braun, M. A1 - Engel, A. A1 - Dikshit, D. A1 - Abbasi, F. A1 - Marti, G.E. A1 - Sassi, M. A1 - Revel, L. A1 - Kim, S.K. A1 - Baradez, M.-O. A1 - Lekishvili, T. A1 - Marshall, D. A1 - Whitby, L. A1 - Jing, W. A1 - Ost, V. A1 - Vonsky, M. A1 - Neukammer, J. T1 - Quantification of cells with specific phenotypes II: Determination of CD4 expression level on reconstituted lyophilized human PBMC labelled with anti-CD4 FITC antibody JF - Cytometry / A N2 - This report focuses on the characterization of CD4 expression level in terms of equivalent number of reference fluorophores (ERF). Twelve different flow cytometer platforms across sixteen laboratories were utilized in this study. As a first step the participants were asked to calibrate the fluorescein isothiocyanate (FITC) channel of each flow cytometer using commercially available calibration standard consisting of five populations of microspheres. Each population had an assigned value of equivalent fluorescein fluorophores (EFF denotes a special case of the generic term ERF with FITC as the reference fluorophore). The EFF values were assigned at the National Institute of Standards and Technology (NIST). A surface-labelled lyophilized cell preparation was provided by the National Institute of Biological Standards and Control (NIBSC), using human peripheral blood mononuclear cells (PBMC) pre-labeled with a FITC conjugated anti-CD4 monoclonal antibody. Three PBMC sample vials, provided to each participant, were used for the CD4 expression analysis. The PBMC are purported to have a fixed number of surface CD4 receptors. On the basis of the microsphere calibration, the EFF value of the PBMC samples was measured to characterize the population average CD4 expression level of the PBMC preparations. Both the results of data analysis performed by each participant and the results of centralized analysis of all participants' raw data are reported. Centralized analysis gave a mean EFF value of 22,300 and an uncertainty of 750, corresponding to 3.3% (level of confidence 68%) of the mean EFF value. The next step will entail the measurement of the ERF values of the lyophilized PBMC stained with labels for other fluorescence channels. The ultimate goal is to show that lyophilized PBMC is a suitable biological reference cell material for multicolor flow cytometry and that it can be used to present multicolor flow cytometry measurements in terms of ABC (antibodies bound per cell) units. KW - Surface labelled lyophilized PBMC KW - CD4 expression level KW - FITC KW - Equivalent fluorescein fluorophore (EFF) KW - Quantitative flow cytometry KW - Calibration KW - Standard measurement procedure KW - Measurement uncertainty KW - Reference cell material PY - 2015 DO - https://doi.org/10.1002/cyto.a.22634 SN - 0196-4763 SN - 1552-4922 SN - 1552-4930 VL - 87 IS - 3 SP - 254 EP - 261 PB - Wiley-Liss CY - Hoboken, NJ AN - OPUS4-32981 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -