@article{SchmidtLiuLiuetal.2014, author = {Schmidt, Sebastian and Liu, Guoxing and Liu, Guilai and Yang, Wenting and Honisch, Sabina and Pantelakos, Stavros and Stournaras, Christos and H{\"o}nig, Arnd and Lang, Florian}, title = {Enhanced Orai1 and STIM1 expression as well as store operated \(Ca^{2+}\) entry in therapy resistant ovary carcinoma cells}, series = {Oncotarget}, volume = {5}, journal = {Oncotarget}, number = {13}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-121423}, pages = {4799-810}, year = {2014}, abstract = {Mechanisms underlying therapy resistance of tumor cells include protein kinase Akt. Putative Akt targets include store-operated \(Ca^{2+}\)-entry (SOCE) accomplished by pore forming ion channel unit Orai1 and its regulator STIM1. We explored whether therapy resistant (A2780cis) differ from therapy sensitive (A2780) ovary carcinoma cells in Akt, Orai1, and STIM1 expression, \(Ca^{2+}\)-signaling and cell survival following cisplatin (100µM) treatment. Transcript levels were quantified with RT-PCR, protein abundance with Western blotting, cytosolic \(Ca^{2+}\)-activity ([\(Ca^{2+}\)]i) with Fura-2-fluorescence, SOCE from increase of [\(Ca^{2+}\)]i following \(Ca^{2+}\)-readdition after Ca2+-store depletion, and apoptosis utilizing flow cytometry. Transcript levels of Orai1 and STIM1, protein expression of Orai1, STIM1, and phosphorylated Akt, as well as SOCE were significantly higher in A2780cis than A2780 cells. SOCE was decreased by Akt inhibitor III (SH-6, 10µM) in A2780cis but not A2780 cells and decreased in both cell lines by Orai1 inhibitor 2-aminoethoxydiphenyl borate (2-ABP, 50µM). Phosphatidylserine exposure and late apoptosis following cisplatin treatment were significantly lower in A2780cis than A2780 cells, a difference virtually abolished by SH-6 or 2-ABP. In conclusion, Orai1/STIM1 expression and function are increased in therapy resistant ovary carcinoma cells, a property at least in part due to enhanced Akt activity and contributing to therapy resistance in those cells.}, language = {en} } @article{RadermacherWinglerKleikersetal.2012, author = {Radermacher, Kim A. and Wingler, Kirstin and Kleikers, Pamela and Altenh{\"o}fer, Sebastian and Hermans, Johannes J. R. and Kleinschnitz, Christoph and Schmidt, Harald H. H. W.}, title = {The 1027th target candidate in stroke: Will NADPH oxidase hold up?}, series = {Experimental and Translational Stroke Medicine}, volume = {4}, journal = {Experimental and Translational Stroke Medicine}, number = {11}, doi = {10.1186/2040-7378-4-11}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-124197}, year = {2012}, abstract = {As recently reviewed, 1026 neuroprotective drug candidates in stroke research have all failed on their road towards validation and clinical translation, reasons being quality issues in preclinical research and publication bias. Quality control guidelines for preclinical stroke studies have now been established. However, sufficient understanding of the underlying mechanisms of neuronal death after stroke that could be possibly translated into new therapies is lacking. One exception is the hypothesis that cellular death is mediated by oxidative stress. Oxidative stress is defined as an excess of reactive oxygen species (ROS) derived from different possible enzymatic sources. Among these, NADPH oxidases (NOX1-5) stand out as they represent the only known enzyme family that has no other function than to produce ROS. Based on data from different NOX knockout mouse models in ischemic stroke, the most relevant isoform appears to be NOX4. Here we discuss the state-of-the-art of this target with respect to stroke and open questions that need to be addressed on the path towards clinical translation.}, language = {en} } @article{HohenauerBerkingSchmidtetal.2013, author = {Hohenauer, Tobias and Berking, Carola and Schmidt, Andreas and Haferkamp, Sebastian and Senft, Daniela and Kammerbauer, Claudia and Fraschka, Sabine and Graf, Saskia Anna and Irmler, Martin and Beckers, Johannes and Flaig, Michael and Aigner, Achim and H{\"o}bel, Sabrina and Hoffmann, Franziska and Hermeking, Heiko and Rothenfusser, Simon and Endres, Stefan and Ruzicka, Thomas and Besch, Robert}, title = {The neural crest transcription factor Brn3a is expressed in melanoma and required for cell cycle progression and survival}, series = {EMBO Molecular Medicine}, volume = {5}, journal = {EMBO Molecular Medicine}, issn = {1757-4676}, doi = {10.1002/emmm.201201862}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-122193}, pages = {919-934}, year = {2013}, abstract = {Pigment cells and neuronal cells both are derived from the neural crest. Here, we describe the Pit-Oct-Unc (POU) domain transcription factor Brn3a, normally involved in neuronal development, to be frequently expressed in melanoma, but not in melanocytes and nevi. RNAi-mediated silencing of Brn3a strongly reduced the viability of melanoma cell lines and decreased tumour growth in vivo. In melanoma cell lines, inhibition of Brn3a caused DNA double-strand breaks as evidenced by Mre11/Rad50-containing nuclear foci. Activated DNA damage signalling caused stabilization of the tumour suppressor p53, which resulted in cell cycle arrest and apoptosis. When Brn3a was ectopically expressed in primary melanocytes and fibroblasts, anchorage-independent growth was increased. In tumourigenic melanocytes and fibroblasts, Brn3a accelerated tumour growth in vivo. Furthermore, Brn3a cooperated with proliferation pathways such as oncogenic BRAF, by reducing oncogene-induced senescence in non-malignant melanocytes. Together, these results identify Brn3a as a new factor in melanoma that is essential for melanoma cell survival and that promotes melanocytic transformation and tumourigenesis.}, language = {en} } @article{TemmeFriebeSchmidtetal.2017, author = {Temme, Sebastian and Friebe, Daniela and Schmidt, Timo and Poschmann, Gereon and Hesse, Julia and Steckel, Bodo and St{\"u}hler, Kai and Kunz, Meik and Dandekar, Thomas and Ding, Zhaoping and Akhyari, Payam and Lichtenberg, Artur and Schrader, J{\"u}rgen}, title = {Genetic profiling and surface proteome analysis of human atrial stromal cells and rat ventricular epicardium-derived cells reveals novel insights into their cardiogenic potential}, series = {Stem Cell Research}, volume = {25}, journal = {Stem Cell Research}, doi = {10.1016/j.scr.2017.11.006}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172716}, pages = {183-190}, year = {2017}, abstract = {Epicardium-derived cells (EPDC) and atrial stromal cells (ASC) display cardio-regenerative potential, but the molecular details are still unexplored. Signals which induce activation, migration and differentiation of these cells are largely unknown. Here we have isolated rat ventricular EPDC and rat/human ASC and performed genetic and proteomic profiling. EPDC and ASC expressed epicardial/mesenchymal markers (WT-1, Tbx18, CD73,CD90, CD44, CD105), cardiac markers (Gata4, Tbx5, troponin T) and also contained phosphocreatine. We used cell surface biotinylation to isolate plasma membrane proteins of rEPDC and hASC, Nano-liquid chromatography with subsequent mass spectrometry and bioinformatics analysis identified 396 rat and 239 human plasma membrane proteins with 149 overlapping proteins. Functional GO-term analysis revealed several significantly enriched categories related to extracellular matrix (ECM), cell migration/differentiation, immunology or angiogenesis. We identified receptors for ephrin and growth factors (IGF, PDGF, EGF, anthrax toxin) known to be involved in cardiac repair and regeneration. Functional category enrichment identified clusters around integrins, PI3K/Akt-signaling and various cardiomyopathies. Our study indicates that EPDC and ASC have a similar molecular phenotype related to cardiac healing/regeneration. The cell surface proteome repository will help to further unravel the molecular details of their cardio-regenerative potential and their role in cardiac diseases.}, language = {en} } @article{VogelPrinzingBussleretal.2021, author = {Vogel, Sebastian and Prinzing, Andreas and Bußler, Heinz and M{\"u}ller, J{\"o}rg and Schmidt, Stefan and Thorn, Simon}, title = {Abundance, not diversity, of host beetle communities determines abundance and diversity of parasitoids in deadwood}, series = {Ecology and Evolution}, volume = {11}, journal = {Ecology and Evolution}, number = {11}, doi = {10.1002/ece3.7535}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-238892}, pages = {6881 -- 6888}, year = {2021}, abstract = {Most parasites and parasitoids are adapted to overcome defense mechanisms of their specific hosts and hence colonize a narrow range of host species. Accordingly, an increase in host functional or phylogenetic dissimilarity is expected to increase the species diversity of parasitoids. However, the local diversity of parasitoids may be driven by the accessibility and detectability of hosts, both increasing with increasing host abundance. Yet, the relative importance of these two mechanisms remains unclear. We parallelly reared communities of saproxylic beetle as potential hosts and associated parasitoid Hymenoptera from experimentally felled trees. The dissimilarity of beetle communities was inferred from distances in seven functional traits and from their evolutionary ancestry. We tested the effect of host abundance, species richness, functional, and phylogenetic dissimilarities on the abundance, species richness, and Shannon diversity of parasitoids. Our results showed an increase of abundance, species richness, and Shannon diversity of parasitoids with increasing beetle abundance. Additionally, abundance of parasitoids increased with increasing species richness of beetles. However, functional and phylogenetic dissimilarity showed no effect on the diversity of parasitoids. Our results suggest that the local diversity of parasitoids, of ephemeral and hidden resources like saproxylic beetles, is highest when resources are abundant and thereby detectable and accessible. Hence, in some cases, resources do not need to be diverse to promote parasitoid diversity.}, language = {en} } @article{JakuscheitSchaeferRoedigetal.2021, author = {Jakuscheit, Axel and Schaefer, Nina and Roedig, Johannes and Luedemann, Martin and Hertzberg-Boelch, Sebastian Philipp von and Weissenberger, Manuel and Schmidt, Karsten and Holzapfel, Boris Michael and Rudert, Maximilian}, title = {Modifiable individual risks of perioperative blood transfusions and acute postoperative complications in total hip and knee arthroplasty}, series = {Journal of Personalized Medicine}, volume = {11}, journal = {Journal of Personalized Medicine}, number = {11}, issn = {2075-4426}, doi = {10.3390/jpm11111223}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-250290}, year = {2021}, abstract = {Background: The primary aim of this study was to identify modifiable patient-related predictors of blood transfusions and perioperative complications in total hip and knee arthroplasty. Individual predictor-adjusted risks can be used to define preoperative treatment thresholds. Methods: We performed this retrospective monocentric study in orthopaedic patients who underwent primary total knee or hip arthroplasty. Multivariate logistic regression models were used to assess the predictive value of patient-related characteristics. Predictor-adjusted individual risks of blood transfusions and the occurrence of any perioperative adverse event were calculated for potentially modifiable risk factors. Results: 3754 patients were included in this study. The overall blood transfusion and complication rates were 4.8\% and 6.4\%, respectively. Haemoglobin concentration (Hb, p < 0.001), low body mass index (BMI, p < 0.001) and estimated glomerular filtration rate (eGFR, p = 0.004) were the strongest potentially modifiable predictors of a blood transfusion. EGFR (p = 0.001) was the strongest potentially modifiable predictor of a complication. Predictor-adjusted risks of blood transfusions and acute postoperative complications were calculated for Hb and eGFR. Hb = 12.5 g/dL, BMI = 17.6 kg/m\(^2\), and eGFR = 54 min/mL were associated, respectively, with a 10\% risk of a blood transfusion, eGFR = 59 mL/min was associated with a 10\% risk of a complication. Conclusion: The individual risks for blood transfusions and acute postoperative complications are strongly increased in patients with a low preoperative Hb, low BMI or low eGFR. We recommend aiming at a preoperative Hb ≥ 13g/dL, an eGFR ≥ 60 mL/min and to avoid a low BMI. Future studies must show if a preoperative increase of eGFR and BMI is feasible and truly beneficial.}, language = {en} } @article{UhlerRedlichZhangetal.2021, author = {Uhler, Johannes and Redlich, Sarah and Zhang, Jie and Hothorn, Torsten and Tobisch, Cynthia and Ewald, J{\"o}rg and Thorn, Simon and Seibold, Sebastian and Mitesser, Oliver and Morin{\`e}re, J{\´e}r{\^o}me and Bozicevic, Vedran and Benjamin, Caryl S. and Englmeier, Jana and Fricke, Ute and Ganuza, Cristina and Haensel, Maria and Riebl, Rebekka and Rojas-Botero, Sandra and Rummler, Thomas and Uphus, Lars and Schmidt, Stefan and Steffan-Dewenter, Ingolf and M{\"u}ller, J{\"o}rg}, title = {Relationships of insect biomass and richness with land use along a climate gradient}, series = {Nature Communications}, volume = {12}, journal = {Nature Communications}, number = {1}, doi = {10.1038/s41467-021-26181-3}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-265058}, year = {2021}, abstract = {Recently reported insect declines have raised both political and social concern. Although the declines have been attributed to land use and climate change, supporting evidence suffers from low taxonomic resolution, short time series, a focus on local scales, and the collinearity of the identified drivers. In this study, we conducted a systematic assessment of insect populations in southern Germany, which showed that differences in insect biomass and richness are highly context dependent. We found the largest difference in biomass between semi-natural and urban environments (-42\%), whereas differences in total richness (-29\%) and the richness of threatened species (-56\%) were largest from semi-natural to agricultural environments. These results point to urbanization and agriculture as major drivers of decline. We also found that richness and biomass increase monotonously with increasing temperature, independent of habitat. The contrasting patterns of insect biomass and richness question the use of these indicators as mutual surrogates. Our study provides support for the implementation of more comprehensive measures aimed at habitat restoration in order to halt insect declines.}, language = {en} } @article{SchmidtZeheHolzgrabe2023, author = {Schmidt, Sebastian and Zehe, Markus and Holzgrabe, Ulrike}, title = {Characterization of binding properties of ephedrine derivatives to human alpha-1-acid glycoprotein}, series = {European Journal of Pharmaceutical Sciences}, volume = {181}, journal = {European Journal of Pharmaceutical Sciences}, doi = {10.1016/j.ejps.2022.106333}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-300848}, year = {2023}, abstract = {Most drugs, especially those with acidic or neutral moieties, are bound to the plasma protein albumin, whereas basic drugs are preferentially bound to human alpha-1-acid glycoprotein (AGP). The protein binding of the long-established drugs ephedrine and pseudoephedrine, which are used in the treatment of hypotension and colds, has so far only been studied with albumin. Since in a previous study a stereoselective binding of ephedrine and pseudoephedrine to serum but not to albumin was observed, the aim of this study was to check whether the enantioselective binding behavior of ephedrine and pseudoephedrine, in addition to the derivatives methylephedrine and norephedrine, is due to AGP and to investigate the influence of their different substituents and steric arrangement. Discontinuous ultrafiltration was used for the determination of protein binding. Characterization of ligand-protein interactions of the drugs was obtained by saturation transfer difference nuclear magnetic resonance spectroscopy. Docking experiments were performed to analyze possible ligand-protein interactions. The more basic the ephedrine derivative is, the higher is the affinity to AGP. There was no significant difference in the binding properties between the individual enantiomers and the diastereomers of ephedrine and pseudoephedrine.}, language = {en} } @phdthesis{Schmidt2023, author = {Schmidt, Sebastian}, title = {A closer look at long-established drugs: enantioselective protein binding and stability studies}, doi = {10.25972/OPUS-34594}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-345945}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {The aim of this work was to investigate older, established drugs. The extent of the protein binding of chiral ephedra alkaloids to AGP and of ketamine to albumin was determined. Since enantiomers of these drugs are individual available, the focus was on possible enantioselective binding and structural moieties involved in the binding. Previously published work suggested that ephedrine and pseudoephedrine can bind stereoselectively to proteins other than albumin in serum. For the determination of the extent of protein binding, the established ultrafiltration with subsequent chiral CE analysis was used. To determine the influence of basicity on binding, the drugs methylephedrine and norephedrine were also analyzed. Drug binding to AGP increased with increasing basicity as follows: norephedrine < methylephedrine < ephedrine < pseudoephedrine. pKaff was determined both graphically using the Klotz plot and mathematical indicating a low affinity of the ephedra alkaloids to AGP. Using STD-NMR spectroscopy experiments the aromatic protons and the C-CH3 side chain were shown to be most strongly involved in binding, which could be confirmed by molecular docking experiments in more detail. For all drugs, van der Waals-, π π , cationic interactions, hydrogen bonds, and a formation of a salt bridge were observed. The individual enantiomers showed no significant differences and thus the binding of ephedra alkaloids to AGP is not significant. In contrast to the ephedra alkaloids, the possible enantioselective binding to albumin was investigated for R and S ketamine. Again, ultrafiltration followed by CE analysis was performed. The binding of ketamine to one main binding site could be identified. A non-linear fit was used for the determination of pKaff. Using the NMR methods STD-NMR, waterLOGSY-NMR, and CPMG-NMRspectroscopy: the aromatic protons as well as the protons of the NCH3 methyl group showed the largest signal intensity changes, while the cyclohexanone protons showed the smallest changes. pKaff was also determined by the change in the chemical shift at different drug-protein ratios. These obtained values confirm the values obtained from ultrafiltration. Based on this, ketamine is classified as a low-affinity ligand to albumin. There were no significant differences between the individual enantiomers and thus the binding of ketamine to albumin is not a stereoselective process. Using statistical design of experiments an efficient chiral CE method for determining the extent of protein binding of R and S ketamine to albumin was developed and validated according to ICH Q2 (R1) guideline. The stability of ketamine was also investigated because a yellowish discoloration of an aqueous solution of ketamine developed under heat. XRPD investigations showed the same crystal structure for all batches examined. An untargeted screening using LC HRMS as well as LC UV measurements showed no degradation of ketamine or the presence of impurities in stress and non-stressed ketamine solutions, confirming the stability of ketamine under the stress conditions investigated. The lower the quality of the water used in the stress tests, the more intense the yellow discoloration occurred. The impurity or the mechanism that causes the yellow discoloration could not be identified.}, subject = {Proteinbindung}, language = {en} } @article{CoelhoKultimaCosteaetal.2018, author = {Coelho, Luis Pedro and Kultima, Jens Roat and Costea, Paul Igor and Fournier, Coralie and Pan, Yuanlong and Czarnecki-Maulden, Gail and Hayward, Matthew Robert and Forslund, Sofia K. and Schmidt, Thomas Sebastian Benedikt and Descombes, Patrick and Jackson, Janet R. and Li, Qinghong and Bork, Peer}, title = {Similarity of the dog and human gut microbiomes in gene content and response to diet}, series = {Microbiome}, volume = {6}, journal = {Microbiome}, doi = {10.1186/s40168-018-0450-3}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-223177}, year = {2018}, abstract = {Background Gut microbes influence their hosts in many ways, in particular by modulating the impact of diet. These effects have been studied most extensively in humans and mice. In this work, we used whole genome metagenomics to investigate the relationship between the gut metagenomes of dogs, humans, mice, and pigs. Results We present a dog gut microbiome gene catalog containing 1,247,405 genes (based on 129 metagenomes and a total of 1.9 terabasepairs of sequencing data). Based on this catalog and taxonomic abundance profiling, we show that the dog microbiome is closer to the human microbiome than the microbiome of either pigs or mice. To investigate this similarity in terms of response to dietary changes, we report on a randomized intervention with two diets (high-protein/low-carbohydrate vs. lower protein/higher carbohydrate). We show that diet has a large and reproducible effect on the dog microbiome, independent of breed or sex. Moreover, the responses were in agreement with those observed in previous human studies. Conclusions We conclude that findings in dogs may be predictive of human microbiome results. In particular, a novel finding is that overweight or obese dogs experience larger compositional shifts than lean dogs in response to a high-protein diet.}, language = {en} } @article{SchmidtHolzgrabe2023, author = {Schmidt, Sebastian and Holzgrabe, Ulrike}, title = {Method development, optimization, and validation of the separation of ketamine enantiomers by capillary electrophoresis using design of experiments}, series = {Chromatographia}, volume = {86}, journal = {Chromatographia}, number = {1}, issn = {0009-5893}, doi = {10.1007/s10337-022-04229-w}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-324713}, pages = {87-95}, year = {2023}, abstract = {Capillary electrophoresis was chosen as cost-effective and robust method to separate ketamine enantiomers. For the method development, first different native and modified cyclodextrins were tested. The most promising chiral selector was α-cyclodextrin. A design of experiments (DoE) was carried out, which started with the screening of relevant factors. Based on these results, the method was optimized according to the significant factors (buffer, cyclodextrin concentration, pH value, voltage, temperature) of the screening based on the response resolution and migration time of the later migrating enantiomer. The optimized conditions consisted of a background electrolyte with 275 mM TRIS, adjusted with 85\% phosphoric acid to a pH of 2.50, and 50 mM α-cyclodextrin, at a temperature of 15 °C, an applied voltage of 30 kV and an injection pressure of 1.0 psi for 10 s. A fused-silica capillary with a total length of 70 cm and an effective length to the detector of 60 cm was used. The method was validated according to ICH guideline Q2 R(1). The limit of quantification was 3.51 µg mL\(^{-1}\) for S-ketamine and 3.98 µg mL\(^{-1}\)for R-ketamine. The method showed good linearity for racemic ketamine with R\(^2\) of 0.9995 for S-ketamine and 0.9994 for R-ketamine. The lowest quantifiable content of S-ketamine found in R-ketamine was 0.45\%.}, language = {en} } @article{TriyasmonoSchollmayerSchmitzetal.2023, author = {Triyasmono, Liling and Schollmayer, Curd and Schmitz, Jens and Hovah, Emilie and Lombo, Cristian and Schmidt, Sebastian and Holzgrabe, Ulrike}, title = {Simultaneous determination of the saponification value, acid value, ester value, and iodine value in commercially available red fruit oil (Pandanus conoideus, Lam.) using \(^1\)H qNMR spectroscopy}, series = {Food Analytical Methods}, volume = {16}, journal = {Food Analytical Methods}, number = {1}, issn = {1936-9751}, doi = {10.1007/s12161-022-02401-4}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-324728}, pages = {155-167}, year = {2023}, abstract = {Red fruit oil (RFO) can be extracted from fruits of Pandanus conoideus, Lam., an endogenous plant of Papua, Indonesia. It is a commonly used essential original traditional medicine. By applying a newly developed quantitative \(^1\)H NMR (qNMR) spectroscopy method for quality assessment, a simultaneous determination of the saponification value (SV), acid value (AV), ester value (EV), and iodine value (IV) in RFO was possible. Dimethyl sulfone (DMSO\(_2\)) was used as an internal standard. Optimization of NMR parameters, such as NMR pulse sequence, relaxation delay time, and receiver gain, finally established the \(^1\)H NMR-based quantification approach. Diagnostic signals of the internal standard at δ = 2.98 ppm, SV at δ = 2.37-2.20 ppm, AV at δ = 2.27-2.20 ppm, EV at δ = 2.37-2.27 ppm, and IV at δ = 5.37-5.27 ppm, respectively, were used for quantitative analysis. The method was validated concerning linearity (R\(^2\) = 0.999), precision (less than 0.83\%), and repeatability in the range 99.17-101.17\%. Furthermore, this method was successfully applied to crude RFO, crude RFO with palmitic and oleic acid addition, and nine commercial products. The qNMR results for the respective fat values are in accordance with the results of standard methods, as can be seen from the F- and t-test (< 1.65 and < 1.66, respectively). The fundamental advantages of qNMR, such as its rapidity and simplicity, make it a feasible and existing alternative to titration for the quality control of RFO.}, language = {en} } @article{SchmidtHolzgrabe2024, author = {Schmidt, Sebastian and Holzgrabe, Ulrike}, title = {Do the enantiomers of ketamine bind enantioselectively to human serum albumin?}, series = {European Journal of Pharmaceutical Sciences}, volume = {192}, journal = {European Journal of Pharmaceutical Sciences}, doi = {10.1016/j.ejps.2023.106640}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-349791}, year = {2024}, abstract = {The binding of drugs to plasma proteins is an important process in the human body and has a significant influence on pharmacokinetic parameter. Human serum albumin (HSA) has the most important function as a transporter protein. The binding of ketamine to HSA has already been described in literature, but only of the racemate. The enantiomerically pure S-ketamine is used as injection solution for induction of anesthesia and has been approved by the Food and Drug Administration for the therapy of severe depression as a nasal spray in 2019. The question arises if there is enantioselective binding to HSA. Hence, the aim of this study was to investigate whether there is enantioselective binding of S-and R-ketamine to HSA or not. Ultrafiltration (UF) followed by chiral capillary electrophoretic analysis was used to determine the extent of protein binding. Bound fraction to HSA was 71.2 \% and 64.9 \% for enantiomerically pure R- and S-ketamine, respectively, and 66.5 \% for the racemate. Detailed binding properties were studied by Saturation Transfer Difference (STD)-, waterLOGSY- and Carr-Purcell-Meiboom-Gill (CPMG)-NMR spectroscopy. With all three methods, the aromatic ring and the N-methyl group could be identified as the structural moieties most strongly involved in binding of ketamine to HSA. pK\(_{aff}\) values determined using UF and NMR indicate that ketamine is a weak affinity ligand to HSA and no significant differences in binding behavior were found between the individual enantiomers and the racemate.}, language = {en} }