| 8111. |
- Arosio, Paolo, et al.
(författare)
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Microfluidic Diffusion Analysis of the Sizes and Interactions of Proteins under Native Solution Conditions.
- 2016
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 10:1, s. 333-341
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Tidskriftsartikel (refereegranskat)abstract
- Characterizing the sizes and interactions of macromolecules under native conditions is a challenging problem in many areas of molecular sciences, which fundamentally arises from the polydisperse nature of biomolecular mixtures. Here, we describe a microfluidic platform for diffusional sizing based on monitoring micron-scale mass transport simultaneously in space and time. We show that the global analysis of such combined space-time data enables the hydrodynamic radii of individual species within mixtures to be determined directly by deconvoluting average signals into the contributions from the individual species. We demonstrate that the ability to perform rapid noninvasive sizing allows this method to be used to characterize interactions between biomolecules under native conditions. We illustrate the potential of the technique by implementing a single-step quantitative immunoassay that operates on a time scale of seconds and detects specific interactions between biomolecules within complex mixtures.
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| 8112. |
- Arshadi, Mehrdad, et al.
(författare)
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Gas chromatography-mass spectrometry determination of the pentafluorobenzoyl derivative of methylhydrazine in false morel (Gyromitra esculenta) as a monitor for the content of the toxin gyromitrin
- 2006
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Ingår i: Journal of Chromatography A. - Amsterdam : Elsevier. - 0021-9673 .- 1873-3778. ; 1125:2, s. 229-233
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Tidskriftsartikel (refereegranskat)abstract
- The main toxic compound found in false morel (Gyromitra esculenta) is acetaldehyde-N-methyl-N-formylhydrazone (gyromitrin). This paper describes a method of determining the total hydrazones content based on acid hydrolysis of gyromitrin and other related hydrazones in air-dried false morel followed by derivatisation of methylhydrazine with pentafluorobenzoyl chloride. The derivative, tris-pentafluorobenzoyl methylhydrazine (tris-PFB-MH) is analyzed by gas chromatography–mass spectrometry. The overall precision of the method is better than 10% (relative standard deviation) for 0.5 ng/μl methylhydrazine in solution. The minimum detectable concentration of methylhydrazine (tris-PFB-MH) by this method is estimated to be approximately 12 pg/μl, which is equal to 0.3 μg/g dry matter (DM) of false morel.
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| 8113. |
- Aslıyüce, Sevgi, et al.
(författare)
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Preparation of Staphylococcal Protein A Imprinted Supermacroporous Cryogel Beads
- 2022
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Ingår i: Methods in Molecular Biology. - New York, NY : Springer US. - 1064-3745 .- 1940-6029. ; 2466, s. 261-273
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Bokkapitel (refereegranskat)abstract
- Protein A is the most commonly used ligand in IgG purification due to its specific binding to the Fc receptor of most immunoglobulins, making it commercially important. Molecular imprinting is a method based on the selective recognition of various molecules. Molecular imprinted polymers are materials that are easy to prepare, durable, cheap and have molecular recognition capability. Cryogels are prepared by radical polymerization in a partially frozen environment. The unique structure of cryogels combined with osmotic, chemical and mechanical stability make them attractive chromatography matrices for a variety of biological compounds/specimens (plasmids, pathogens, cells). In this protocol, protein A imprinted supermacroporous poly(2-hydroxyethyl methacrylate) cryogels were prepared in spherical form for protein A purification. The characterization of the prepared cryogels were made by swelling test, scanning electron microscopy (SEM), Fourier transform infrared spectrophotometer (FTIR), and Brunauer–Emmett–Teller (BET) surface area analysis. After characterization, optimum conditions for protein A adsorption were determined in the batch system. The maximum protein A adsorption capacity was determined after optimization of the imprinted cryogels. Protein A relative selectivity coefficients of imprinted cryogels were examined for both Fc and protein G. Protein A was isolated from the bacterial cell wall using fast performance liquid chromatography (FPLC). The separated protein A was determined by sodium dodecyl sulfate gel electrophoresis (SDS-PAGE). In the last stage, the reusability of the cryogel was examined.
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| 8114. |
- Aureliano, Manuel, et al.
(författare)
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Characterization of decavanadate and decaniobate solutions by Raman spectroscopy
- 2016
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 45:17, s. 7391-7399
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Tidskriftsartikel (refereegranskat)abstract
- The decaniobate ion, (Nb-10 = [Nb10O28](6-)) being isoelectronic and isostructural with the decavanadate ion (V-10 = [V10O28](6-)), but chemically and electrochemically more inert, has been useful in advancing the understanding of V-10 toxicology and pharmacological activities. In the present study, the solution chemistry of Nb-10 and V-10 between pH 4 and 12 is studied by Raman spectroscopy. The Raman spectra of V-10 show that this vanadate species dominates up to pH 6.45 whereas it remains detectable until pH 8.59, which is an important range for biochemistry. Similarly, Nb-10 is present between pH 5.49 and 9.90 and this species remains detectable in solution up to pH 10.80. V-10 dissociates at most pH values into smaller tetrahedral vanadate oligomers such as V-1 and V-2, whereas Nb-10 dissociates into Nb-6 under mildly (10 > pH > 7.6) or highly alkaline conditions. Solutions of V-10 and Nb-10 are both kinetically stable under basic pH conditions for at least two weeks and at moderate temperature. The Raman method provides a means of establishing speciation in the difficult niobate system and these findings have important consequences for toxicology activities and pharmacological applications of vanadate and niobate polyoxometalates.
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| 8115. |
- Azuma, Tomoyuki, et al.
(författare)
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Enhancement of Cell Adhesion on a Phosphorylcholine-Based Surface through the Interaction with DNA Mediated by Ca2+ Ions
- 2016
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 120:48, s. 12272-12278
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Tidskriftsartikel (refereegranskat)abstract
- 2-Methacryloyloxyethyl phosphorylcholine (MPC) has a PC group and is one of the most well-known bioinert polymers. In this study, we evaluated the interaction between MPC and DNA, which specifically interacts with the phospholipid head group via Ca2+ ions. A MPC monolayer and poly(MPC) brush were fabricated to observe the effect of the structure on the interaction between MPC and DNA via Ca2+ ions. The poly(MPC) brush, which shows higher MPC unit density, more efficiently interacted with DNA via Ca2+ ions. Also, serum protein could interact with the poly(MPC) brush via DNA, although the brush itself hardly interacted with serum proteins. Cell adhesion was significantly provoked on poly(MPC)/DNA compared with poly(MPC) because serum protein adsorption was induced on poly(MPC)/DNA.
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| 8116. |
- Azuma, Tomoyuki, et al.
(författare)
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Poly(2-aminoethyl methacrylate)-based polyampholyte brush surface with carboxylic groups to improve blood compatibility
- 2020
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Ingår i: Journal of Biomaterials Science. Polymer Edition. - : Taylor & Francis Group. - 0920-5063 .- 1568-5624. ; 31:5, s. 679-693
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Tidskriftsartikel (refereegranskat)abstract
- Zwitterionic material-based polymer brush significantly prevents protein adsorption and cell adhesion, which leads to the blood compatibility. However, zwitterionic polymer itself is difficult to be modified further, for the blood compatibility since the charged balance is impaired after the modification. In this research, chemically modifiable mixed charge polymer brush is designed, without impairing its characteristics. Condensed mixed charge polymer brush will work like zwitterionic material because neighbouring opposite charge is reported to be important in the zwitterionic material. Cationic polymer brush with primary amine group, which is based on 2-aminoethyl methacrylate (AEMA), was prepared and modified by succinic anhydride to obtain carboxylic group induced poly(AEMA). The ratio of primary amine group and carboxylic group was optimized to obtain the polyampholyte brush. The blood compatibility was evaluated by measuring coagulation/complement activation, protein adsorption and cell adhesion induced by the polymer. Our designed cationic-based polyampholyte brush prevented coagulation/complement activation comparable to poly(2-methacryloyloxyethyl phosphorylcholine) brush, based on intra-monomer interaction, because condensed mix charge works like zwitterion.
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| 8117. |
- Bankefors, Johan, et al.
(författare)
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Electrospray ionization ion-trap multiple-stage mass spectrometry of Quillaja saponins
- 2011
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 46, s. 658-665
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Tidskriftsartikel (refereegranskat)abstract
- Fifteen identified C-18 fatty acyl-containing saponin structures from Quillaja saponaria Molina have been investigated by electrospray ionization ion-trap multiple-stage mass spectrometry (ESI-IT-MS(n)) in positive ion mode. Their MS(1)-MS(3) spectra were analyzed and ions corresponding to useful fragments, important for the structural identification of Quillaja saponins, were recognized. A few key fragments could describe the structural variations in the C-3 and the C-28 oligosaccharides of the Quillaja saponins. A flowchart involving a stepwise procedure based on key fragments from the MS(1)-MS(3) spectra of these saponins, together with key fragments from these saponins and 13 previously investigated saponins, was constructed for the identification of structural elements in Quillaja saponins. Peak intensity ratios in MS(3) spectra were found to be correlated to structural features of the investigated saponins and is therefore of value for the identification of regioisomers. Copyright (C) 2011 John Wiley & Sons, Ltd.
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| 8118. |
- Bar, Laure, et al.
(författare)
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Impact of antigen density on recognition by monoclonal antibodies
- 2020
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Ingår i: Analytical Biochemistry. - : American Chemical Society (ACS). - 0003-2697 .- 1096-0309 .- 0003-2700 .- 1520-6882. ; 92:7, s. 5396-5403
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Tidskriftsartikel (refereegranskat)abstract
- Understanding antigen–antibody interactions is important to many emerging medical and bioanalytical applications. In particular, the levels of antigen expression at the cell surface may determine antibody-mediated cell death. This parameter has a clear effect on outcome in patients undergoing immunotherapy. In this context, CD20 which is expressed in the membrane of B cells has received significant attention as target for immunotherapy of leukemia and lymphoma using the monoclonal antibody rituximab. To systematically study the impact of CD20 density on antibody recognition, we designed self-assembled monolayers that display tunable CD20 epitope densities. For this purpose, we developed in situ click chemistry to functionalize SPR sensor chips. We find that the rituximab binding affinity depends sensitively and nonmonotonously on CD20 surface density. Strongest binding, with an equilibrium dissociation constant (KD = 32 nM) close to values previously reported from in vitro analysis with B cells (apparent KD between 5 and 19 nM), was obtained for an average inter-antigen spacing of 2 nm. This distance is required for improving rituximab recognition, and in agreement with the known requirement of CD20 to form clusters to elicit a biological response. More generally, this study offers an interesting outlook in the understanding of the necessity of epitope clusters for effective mAb recognition.
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| 8119. |
- Barchan, Nikolina, et al.
(författare)
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Synthesis of glycophospholipid conjugates with mono- and disaccharides by enzymatic transphosphatidylation
- 2024
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Ingår i: European Journal of Lipid Science and Technology. - 1438-7697. ; 126:3
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Tidskriftsartikel (refereegranskat)abstract
- Phospholipids, PLs, are interesting and highly abundant amphiphilic molecules, which self-assemble into 3D nanostructures that have big interest as formulation excipients in, for example, pharma industry. However, the structures that are formed by naturally occurring PLs usually suffer from rigidity problems, and the nanostructures have to be modified in various ways for improved stability. One such approach is by the conjugation of saccharides to the PL head group. In this study, we investigate reaction conditions for the scalable phospholipase D–catalyzed transphosphatidylation reaction for the synthesis of glycophospholipids. Biphasic reaction systems with different solvents are compared with a purely aqueous system with PLs dispersed as vesicles. The investigations showed that use of the biphasic system containing chloroform and a glucose/phosphatidylcholine ratio of 50, in combination with carefully selected enzyme concentration and reaction time, led to an optimized process without any hydrolytic side reaction for the synthesis of phosphatidyl glucose. The reaction system was then applied to a variety of different mono- and disaccharides for the synthesis of a range of different glycophospholipids, resulting in yields up to 85% of phosphatidyl monosaccharides and 35% of disaccharides. Practical Application: Phospholipids and other polar lipids are of great scientific interest as formulation excipients. The chemical structures of lipids used for such applications have major impact on the properties of the self-aggregated systems. Synthesis of new phospholipids with modified head groups can tremendously widen the portfolio of available choices of formulation excipients and make it possible to make customized formulations with the desired properties. The introduction of saccharides in the hydrophilic part of the phospholipid alters the chemistry of head group and its interaction with surrounding water in vesicle systems and should therefore have a significant effect on its formulating properties compared to natural phospholipids.
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| 8120. |
- Barreto, L., et al.
(författare)
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A peroxisomal glutathione transferase of Saccharomyces cerevisiae is functionally related to sulfur amino acid metabolism
- 2006
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Ingår i: Eukaryot Cell. ; 5:10, s. 1748-59
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Tidskriftsartikel (refereegranskat)abstract
- Saccharomyces cerevisiae cells contain three omega-class glutathione transferases with glutaredoxin activity (Gto1, Gto2, and Gto3), in addition to two glutathione transferases (Gtt1 and Gtt2) not classifiable into standard classes. Gto1 is located at the peroxisomes, where it is targeted through a PTS1-type sequence, whereas Gto2 and Gto3 are in the cytosol. Among the GTO genes, GTO2 shows the strongest induction of expression by agents such as diamide, 1-chloro-2,4-dinitrobenzene, tert-butyl hydroperoxide or cadmium, in a manner that is dependent on transcriptional factors Yap1 and/or Msn2/4. Diamide and 1-chloro-2,4-dinitrobenzene (causing depletion of reduced glutathione) also induce expression of GTO1 over basal levels. Phenotypic analyses with single and multiple mutants in the S. cerevisiae glutathione transferase genes show that, in the absence of Gto1 and the two Gtt proteins, cells display increased sensitivity to cadmium. A gto1-null mutant also shows growth defects on oleic acid-based medium, which is indicative of abnormal peroxisomal functions, and altered expression of genes related to sulfur amino acid metabolism. As a consequence, growth of the gto1 mutant is delayed in growth medium without lysine, serine, or threonine, and the mutant cells have low levels of reduced glutathione. The role of Gto1 at the S. cerevisiae peroxisomes could be related to the redox regulation of the Str3 cystathionine beta-lyase protein. This protein is also located at the peroxisomes in S. cerevisiae, where it is involved in transulfuration of cysteine into homocysteine, and requires a conserved cysteine residue for its biological activity.
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