scholarly journals Studies on Enzymatic Crosslinking of Casein Micelles

2009 ◽  
Vol 27 (Special Issue 1) ◽  
pp. S99-S101 ◽  
Author(s):  
C. Partschefeld ◽  
J. Schreiner ◽  
U. Schwarzenbolz ◽  
T. Henle
Keyword(s):  
Analytical Methods ◽  
Outer Space ◽  
Gel Permeation Chromatography ◽  
Microbial Transglutaminase ◽  
Enzymatic Modification ◽  
Casein Micelles ◽  
Micellar Structure ◽  
Rp Hplc ◽  
Gel Permeation ◽  
Beta Casein

The aim of our study was to gain insights into the reactions occurring in casein micelles during enzymatic modification with microbial transglutaminase (mTG). Therefore, UHT-treated milk was incubated with varying amounts of mTG and the caseins were analysed using different analytical methods. Regarding the casein species, it was observed that β -casein was crosslinked to a higher extent than the α-caseins. From this it can be suggested that β-casein is mainly located in the outer space of the micellar structure and therefore better accessible to mTG than α-caseins, which are located predominantly in the interior. Furthermore, it was demonstrated by gel-permeation chromatography and RP-HPLC that the caseins are fixed within the micellar structure, by what the ratio of extramicellar casein decreased. We conclude that an isopeptide network in the outer β -casein rich “shell” of the micelle is formed by mTG, which is responsible for the increased micellar stability.

Aggregated, Conformationally Changed Fibrinogen Exposes the Stimulating Sites for t-PA-Catalysed Plasminogen Activation

1996 ◽  
Vol 75 (02) ◽  
pp. 326-331 ◽  
Author(s):  
Unni Haddeland ◽  
Knut Sletten ◽  
Anne Bennick ◽  
Willem Nieuwenhuizen ◽  
Frank Brosstad
Keyword(s):  
Conformational Changes ◽  
Gel Permeation Chromatography ◽  
Tissue Type ◽  
Plasminogen Activation ◽  
Chromogenic Substrate ◽  
Type Plasminogen Activator ◽  
Gel Permeation ◽  
Self Association ◽  
Fibrin Monomers ◽  
Stimulation Of

SummaryThe present paper shows that conformationally changed fibrinogen can expose the sites Aα-(148-160) and γ-(312-324) involved in stimulation of the tissue-type plasminogen activator (t-PA)-catalysed plasminogen activation. The exposure of the stimulating sites was determined by ELISA using mABs directed to these sites, and was shown to coincide with stimulation of t-PA-catalysed plasminogen activation as assessed in an assay using a chromogenic substrate for plasmin. Gel permeation chromatography of fibrinogen conformationally changed by heat (46.5° C for 25 min) demonstrated the presence of both aggregated and monomeric fibrinogen. The aggregated fibrinogen, but not the monomeric fibrinogen, had exposed the epitopes Aα-(148-160) and γ-(312-324) involved in t-PA-stimulation. Fibrinogen subjected to heat in the presence of 3 mM of the tetrapeptide GPRP neither aggregates nor exposes the rate-enhancing sites. Thus, aggregation and exposure of t-PA-stimulating sites in fibrinogen seem to be related phenomena, and it is tempting to believe that the exposure of stimulating sites is a consequence of the conformational changes that occur during aggregation, or self-association. Fibrin monomers kept in a monomeric state by a final GPRP concentration of 3 mM do not expose the epitopes Aα-(148-160) and γ-(312-324) involved in t-PA-stimulation, whereas dilution of GPRP to a concentration that is no longer anti-polymerizing, results in exposure of these sites. Consequently, the exposure of t-PA-stimulating sites in fibrin as well is due to the conformational changes that occur during selfassociation.

Gel Permeation Chromatography of Polyelectrolytes

1981 ◽  
Vol 4 (8) ◽  
pp. 1297-1309 ◽  
Author(s):  
M. Rinaudo ◽  
J. Desbrières ◽  
C. Rochas
Keyword(s):  
Gel Permeation Chromatography ◽  
Gel Permeation

scholarly journals Molar mass determination of lignins and characterization of their polymeric structures by multi-detector gel permeation chromatography

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Evamaria C. Gaugler ◽  
Wolfgang Radke ◽  
Andrew P. Vogt ◽  
Dawn A. Smith
Keyword(s):  
Molar Mass ◽  
Lithium Bromide ◽  
Gel Permeation Chromatography ◽  
Mass Determination ◽  
Organosolv Lignin ◽  
Gel Permeation ◽  
Softwood Kraft Lignin ◽  
Polymeric Structures

AbstractMolar masses, Mark-Houwink-Sakurada (MHS) exponents, and refractive index increments (dn/dc) for three lignins were determined without derivatization by multi-detector gel permeation chromatography (GPC) in dimethylformamide (DMF) with 0.05 M lithium bromide (LiBr). The lack of effectiveness of fluorescence filters on molar mass determination by GPC-multi-angle laser light scattering (MALS) was confirmed for softwood kraft lignin (Indulin AT) and revealed for mixed hardwood organosolv lignin (Alcell) as well as soda straw/grass lignin (Protobind 1000). GPC with viscometry detection confirmed that these lignins were present as compact molecules. The MHS exponent α for Indulin AT and Alcell was in the order of 0.1. Additionally, the intrinsic viscosity of Protobind 1000 for a given molar mass was much lower than that of either Alcell or Indulin AT. This is the first report of dn/dc values for these three lignins in DMF with 0.05 M LiBr.

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