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- Breccia, Javier D, et al.
(författare)
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The role of poly(ethyleneimine) in stabilization against metal-catalyzed oxidation of proteins: a case study with lactate dehydrogenase.
- 2002
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Ingår i: Biochimica et Biophysica Acta. General Subjects. - 0304-4165. ; 1570:3, s. 165-173
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Tidskriftsartikel (refereegranskat)abstract
- The protection provided by poly(ethyleneimine) (PEI) to muscle lactate dehydrogenase (LDH) in metal-catalyzed oxidation (MCO) systems (CuSO(4) or FeCl(2) combined with H(2)O(2)) was studied, and comparisons were made with the chelators EDTA and desferal, respectively. The analytical chelating capacity of PEI was estimated to be around 1 mol Cu(2+)/10 mol ethyleneimine for all molecular weights of the polymer. The effect of [PEI monomer]/[metal ion] molar ratio on the oxidatively induced aggregation of LDH exhibited a similar trend as that of the other chelators; aggregation was enhanced at lower ratios and subsequently decreased until it was undetectable with increasing ratio. In contrast, the LDH activity showed a monotonic increase with increasing concentrations of the chelator. Total protection to the enzyme by PEI was provided at concentrations lower than that needed for full chelation of the copper ions, i.e. at [PEI monomer]/[Cu(2+)] ratio above 9 in case of PEI 2000, and above 7 for PEI 25000 and 2.6 x 10(6), respectively. The polymer also provided protection against oxidation in an iron-based MCO system. Hydroxyl radical formation during the MCO reaction was inhibited in the presence of PEI. The polymer of higher molecular weights also exhibited a stronger free radical scavenging effect.
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- Mazzaferro, Laura, et al.
(författare)
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Polyethyleneimine-protein interactions and implications on protein stability
- 2010
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 1879-0003 .- 0141-8130. ; 47:1, s. 15-20
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Tidskriftsartikel (refereegranskat)abstract
- Protein stability assessment of seven model proteins in the presence of low molecular weight polyethyleneimine (PEI, MW 2000 Da) was performed. Thermodynamic stability, monitored by circular dichroism (CD) spectroscopy, showed that the polymer did not have a major effect on the melting temperature (T-m) of the basic proteins - muscle lactate dehydrogenase (LDH), ribonuclease A, lysozyme and cutinase, while for the acidic ones - human growth hormone, human serum albumin and heart lactate dehydrogenase - there was a shift in T-m towards lower temperatures. The secondary structures of the basic proteins were essentially the same, with none or a slight increase in the CD spectra, in presence of the polymer. In the case of the acidic proteins, the CD spectra were diminished mostly due to phase separation. Assuming a homogeneous distribution of the net charge on the protein surface a quantitative inverse relationship was established between surface charge density of the acidic proteins and the PEI2000 concentration required for maximum flocculation. Despite lowering the thermal stability of acidic proteins, PEI2000 was seen to protect heart LDH at an increasing oxidative stress. (C) 2010 Elsevier B.V. All rights reserved.
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