0000000000046950
AUTHOR
Thomas Nawroth
showing 26 related works from this author
Application of a three-dimensional drawing procedure to the evaluation of series of protein samples after analysis by gel electrophoresis and other m…
1981
Rapid detergent exchange in solutions of the membrane protein bacteriorhodopsin by preparative high-performance liquid chromatography (HPLC)
1984
ERA-experiment “space biochemistry”
1995
Abstract The general goal of the experiment was to study the response of anhydrobiotic (metabolically dormant) microorganisms (spores of Bacillus subtilis, cells of Deinococcus radiodurans, conidia of Aspergillus species) and cellular constituents (plasmid DNA, proteins, purple membranes, amino acids, urea) to the extremely dehydrating conditions of open space, in some cases in combination with irradiation by solar UV-light. Methods of investigation included viability tests, analysis of DNA damages (strand breaks, DNA-protein cross-links) and analysis of chemical effects by spectroscopic, electrophoretic and chromatographic methods. The decrease in viability of the microorganisms was as exp…
Liposome Formation from Bile Salt–Lipid Micelles in the Digestion and Drug Delivery Model FaSSIFmod Estimated by Combined Time-Resolved Neutron and D…
2011
The flow of bile secretion into the human digestive system was simulated by the dilution of a bile salt-lipid micellar solution. The structural development upon the dilution of the fed state bile model FeSSIF(mod6.5) to the fasted state bile model FaSSIF(mod) was investigated by small-angle neutron scattering (SANS) and dynamic light scattering (DLS) in crossed beam experiments to observe small and large structures in a size range of 1 nm to 50 μm in parallel. Because of the physiologically low lipid and surfactant concentrations of 2.625 mM egg-phosphatidylcholine and 10.5 mM taurocholate the sensitivity of the neutron-structural investigations was improved by partial solvent deuteration w…
Isolation and partial characterization of a cytochrome-o complex from chromatophores of the photosynthetic bacterium Rhodospirillum rubrum FR1.
1989
A cytochrome-o complex was isolated from chromatophores of photoheterotrophically grown Rhodospirillum rubrum FR1. The enzyme was extracted with the non-denaturating detergent taurodeoxycholate and subsequently purified by sucrose-density-gradient centrifugation and gel-permeation HPLC. The complex contains two types of cytochromes, one of them cytochrome o, and two copper atoms. It catalyzes the reduction of molecular oxygen, when N,N,N',N'-tetramethyl-p-phenylenediamine or ubiquinol 10 are offered as electron donors. The oxidase activity is inhibited by cyanide, carbon monoxide and 2-heptyl-2-hydroxyquinoline N-oxide. The molecular mass of the protein is 136 +/- 15 kDa. The subunit analys…
Hemin-coupled iron(III)-hydroxide nanoparticles show increased uptake in Caco-2 cells
2011
Abstract Objectives The absorption of commonly used ferrous iron salts from intestinal segments at neutral to slightly alkaline pH is low, mainly because soluble ferrous iron is easily oxidized to poorly soluble ferric iron and ferrous iron but not ferric iron is carried by the divalent metal transporter DMT-1. Moreover, ferrous iron frequently causes gastrointestinal side effects. In iron(III)-hydroxide nanoparticles hundreds of ferric iron atoms are safely packed in nanoscaled cores surrounded by a solubilising carbohydrate shell, yet bioavailability from such particles is insufficient when compared with ferrous salts. To increase their intestinal uptake iron(III)-hydroxide nanoparticles …
Purification of a cytochrome aa3 terminal oxidase from protoplast membrane vesicles of Micrococcus luteus
1994
Abstract A cytochrome aa 3 terminal oxidase was isolated from protoplast membrane vesicles of Micrococcus luteus grown under aerobic conditions. The purified complex showed similarities to cytochrome c oxidase (EC 1.9.3.1) of the electron transport chain of mitochondria and many prokaryotes. The enzyme was solubilized by subsequent treatment with the detergents CHAPS and n- dodecyl -β- d - maltoside and purified by ion-exchange chromatography using poly- l -lysine agarose and TMAE-fractogel-650 (S) columns, followed by hydroxyapatite chromatography. The purified complex is composed of two major subunits with apparent molecular masses of 54 and 32 kDa. After purification the isolated enzyme …
Hyperbranched Polyglycerol-Based Lipids via Oxyanionic Polymerization: Toward Multifunctional Stealth Liposomes
2010
We describe the synthesis of linear-hyperbranched lipids for liposome preparation based on linear poly(ethylene glycol) (PEG) and hyperbranched polyglycerol (PG). Molecular weights were adjusted to values around 3000 g/mol with varying degrees of polymerization of the linear and the branched segments in analogy to PEG-based stealth lipids; polydispersities were generally low and below 1.3. The hydrophobic anchors were introduced into the lipid structures as initiators for the anionic polymerization of ethylene oxide and are either based on cholesterol or on different aliphatic glyceryl ethers. Complete incorporation of the apolar initiators was evidenced by MALDI-ToF analysis at all stages …
Iron Oxide/Hydroxide Nanoparticles with Negatively Charged Shells Show Increased Uptake in Caco-2 Cells
2012
The absorption of commonly used ferrous iron salts from intestinal segments at neutral to slightly alkaline pH is low, mainly because soluble ferrous iron is easily oxidized to poorly soluble ferric iron and because ferrous iron, but not ferric iron, is carried by the divalent metal transporter DMT-1. Moreover, ferrous iron frequently causes gastrointestinal side effects. Iron hydroxide nanoparticles with neutral and hydrophilic carbohydrate shells are alternatively used to ferrous salts. In these formulations gastrointestinal side effects are rare because hundreds of ferric iron atoms are safely packed in nanoscaled cores surrounded by the solubilizing shell; nevertheless, iron bioavailabi…
A Novel Disintegration Tester for Solid Dosage Forms Enabling Adjustable Hydrodynamics.
2016
A modified in vitro disintegration test device was designed that enables the investigation of the influence of hydrodynamic conditions on disintegration of solid oral dosage forms. The device represents an improved derivative of the compendial PhEur/USP disintegration test device. By the application of a computerized numerical control, a variety of physiologically relevant moving velocities and profiles can be applied. With the help of computational fluid dynamics, the hydrodynamic and mechanical forces present in the probe chamber were characterized for a variety of device moving speeds. Furthermore, a proof of concept study aimed at the investigation of the influence of hydrodynamic condi…
Preparative separation of phospholipids by flash-HPLC
1988
Hybrid Biopolymer and Lipid Nanoparticles with Improved Transfection Efficacy for mRNA
2020
Cells 9(9), 2034 (1-19) (2020). doi:10.3390/cells9092034
Structural dynamics in F1ATPase during the first reaction cycle of ATP hydrolysis
1991
Abstract The velocity of ATP hydrolysis, catalyzed by purified F 1 ATPase from Micrococcus luteus , was decelerated on decreasing the temperature. At 13′C one reaction cycle is completed after 20 s. Hydrolysis was triggered upon rapid mixing of the enzyme with ATP. During the first reaction cycle, succeeding structural alterations of the F 1 ATPase were traced by time resolved X-ray scattering. The scattering spectra obtained from consecutive intervals of 1 s, revealed the F 1 ATPase to pass a conformational state exhibiting an expanded (6%) molecular shape. The expanded state was observed between 45% and 65% of the time required to complete the reaction cycle. This pointx out a conformatio…
Purification of ATP synthase from beef heart mitochondria (FoF1) and co-reconstitution with monomeric bacteriorhodopsin into liposomes capable of lig…
1993
ATP synthase was isolated from beef heart mitochondria by extraction with N,N-bis-(3-D-gluconamidopropyl)deoxycholamide or by traditional cholate extraction. The enzyme was purified subsequently by ion-exchange and gel-permeation chromatographies in the presence of glycerol and the protease inhibitor diisopropylfluorophosphate. The ATP synthase consisted of 12–14 subunits and contained three tightly bound nucleotides. The co-reconstitution of crude or purified ATP synthase with monomeric bacteriorhodopsin by the method of detergent incubation of liposomes yielded proteoliposomes capable of light-driven ATP synthesis, as detected with a luciferase system for at least 30 min. The reaction was…
111 Bioluminescence analysis and numerical evaluation of ATP-synthesis by native and reconstituted membranes containing bacterial ATP-synthase
1992
ATP-synthase is a large membrane protein complex, which plays a key role in the energy metabolism of most organisms. It consists of at least eight types of subunits and can be isolated and purified from several organisms, e.g. bacteria. The enzyme couples two reversible reactions: vectorial proton transport through a membrane and synthesis of the energy rich molecule ATP. Both can be investigated with vesicles from native membranes or with reconstituted liposomes from purified ATPsynthase. The analysis is complicated because ATP-synthase catalyzes ATP-synthesis as well as ATP-hydrolysis. Furthermore the ATP level of membrane samples is influenced by adenylate kinase activities of other enzy…
Investigation of charge ratio variation in mRNA – DEAE-dextran polyplex delivery systems
2019
Biomaterials 192, 612 - 620 (2019). doi:10.1016/j.biomaterials.2018.10.020
A comparative study of the physicochemical properties of iron isomaltoside 1000 (Monofer®), a new intravenous iron preparation and its clinical impli…
2011
Abstract The treatment of iron deficiency anemia with polynuclear iron formulations is an established therapy in patients with chronic kidney disease but also in other disease areas like gastroenterology, cardiology, oncology, pre/post operatively and obstetrics’ and gynecology. Parenteral iron formulations represent colloidal systems in the lower nanometer size range which have traditionally been shown to consist of an iron core surrounded by a carbohydrate shell. In this publication, we for the first time describe the novel matrix structure of iron isomaltoside 1000 which differs from the traditional picture of an iron core surrounded by a carbohydrate. Despite some structural similaritie…
Nanoparticle Size Is a Critical Physicochemical Determinant of the Human Blood Plasma Corona: A Comprehensive Quantitative Proteomic Analysis
2011
In biological fluids, proteins associate with nanoparticles, leading to a protein "corona" defining the biological identity of the particle. However, a comprehensive knowledge of particle-guided protein fingerprints and their dependence on nanomaterial properties is incomplete. We studied the long-lived ("hard") blood plasma derived corona on monodispersed amorphous silica nanoparticles differing in size (20, 30, and 100 nm). Employing label-free liquid chromatography mass spectrometry, one- and two-dimensional gel electrophoresis, and immunoblotting the composition of the protein corona was analyzed not only qualitatively but also quantitatively. Detected proteins were bioinformatically cl…
110 Membrane labeling by colored lipid-analogues and photoaffinity labeling of membrane proteins by colored hydrophobic azido-probes
1992
Fasted-state simulated intestinal fluid "FaSSIF-C", a cholesterol containing intestinal model medium for in vitro drug delivery development.
2015
A set of biorelevant media "fasted-state simulated intestinal fluid with cholesterol (FaSSIF-C)" for the in vitro study of intestinal drug dissolution in the duodenum was developed. These contain cholesterol at the same levels as in human bile: the cholesterol content of FaSSIF-7C is equivalent to healthy female, FaSSIF-10C to healthy male persons, and FaSSIF-13C to several disease cases that lead to gallstones. The fluids were studied in three aspects: biocompatibility, intestinal nanostructure, and solubilizing power of hydrophobic drugs of the BCS class II. The biocompatibility study showed no toxic effects in a Caco-2 cell system. The drug-solubilizing capacity toward Fenofibrate, Danaz…
Nanoparticle structure development in the gastro‐intestinal model fluid FaSSIF mod6.5 from several phospholipids at various water content relevant fo…
2014
The characteristics of intestinal model fluids were investigated at conditions, which simulate the passage from the middle to the end of the duodenum. The formation and decay of liposomes and micelles in model bile fluids were studied, because of their role as an intermediate host for the resolution and uptake of hydrophobic drugs (BCS classes II, IV). The conditions, which may influence the formation of these nanoparticulate intermediates were studied, i.e., the lipid composition of the bile, the preparation method, the time of the passage through the modelled duodenum segment and the concentration, which results from the variable dilution of the bile by mixing with the transfer medium rep…
Purification and molecular weight determination of the membrane protein cytochrome o-complex from Rhodospirillum rubrum by high-performance liquid ch…
1988
Reconstitution of bacteriorhodopsin and ATP synthase from Micrococcus luteus into liposomes of the purified main tetraether lipid from Thermoplasma a…
1995
The archaebacterium Thermoplasma acidophilum is cultivated at 59 degrees C in a medium containing sulfuric acid of pH 2. The purified bipolar membrane spanning main phospholipid (MPL) of this organism can be used to produce stable liposomes of 100-500 nm in diameter either using a French pressure cell detergent dialysis or sonication. Despite a potassium diffusion potential of 186 mV very low ionic permeability of sonicated MPL liposomes was measured using the potassium binding fluorescent indicator benzofuran isophthalate PBF1, which measures net K+ uptake. The latter also remained very low, in the presence of the K(+) ionophore valinomycin and palmitic acid. Addition of valinomycin and th…
Time-dependent monomerization of bacteriorhodopsin in triton X-100 solutions analyzed by high-performance liquid chromatography
1984
Abstract Bacteriorhodopsin from Halobacterium halobium was monomerized in Triton X-100 solutions. The process of delipidation was monitored by size-exclusion high-performance liquid chromatography under conditions that preserved the native conformation of the protein. The effects on the process of monomerization of the concentration and pH of the Triton X-100 solutions were investigated. The monomeric bacteriorhodopsin separated was active in light-dependent proton translocation when incorporated into soy bean lecithin liposomes.
Comparison of Dialysis and Dispersion Methods for In Vitro Release Determination of Drugs from Multilamellar Liposomes
2008
The aim of these studies was to compare dialysis and dispersion methods for determining in vitro release of propranolol, metoprolol, pindolol, and atenolol from multilamellar liposomes. Multilamellar vesicles (MLV) were prepared using hydrogenated soy-lecithin phospholipon 90H (Ph 90H) as the primary lipid. The same volume of pH 7.4 phosphate buffered saline was used as a receptor medium for both methods. Samples were withdrawn, and drug concentration was determined using HPLC. All drug-containing liposomes exhibited an initial burst release followed by a slower rate of release. The rate and extent of drug release from MLV was dependent on the physicochemical properties of the drug. For all…