Human Red Cells Research Articles

Detecting extracellular carbonic anhydrase activity using membrane inlet mass spectrometry

Current research into the function of carbonic anhydrases (CAs) in cell physiology emphasizes the role of membrane-bound CAs such as CA IX, which has been identified in malignant tumors and is associated with extracellular acidification as a response to hypoxia. Here we present a mass spectrometric method to determine the extent to which total CA activity is due to extracellular CA in whole cell preparations. The method is based on the biphasic rate of depletion of 18O from CO2 measured by membrane inlet mass spectrometry. The slopes of the biphasic depletion are a sensitive measure of the presence of CA inside and outside of the cells. This property is demonstrated here using suspensions of human red cells in which external CA was added to the suspending solution. It is also applied to breast and prostate cancer cells, both of which express exofacial CA IX. Inhibition of external CA is achieved by the use of a membrane impermeant inhibitor that was synthesized for this purpose, p-aminomethylbenzenesulfonamide attached to a polyethylene glycol polymer.

A Fused α-β “Mini-spectrin” Mimics the Intact Erythrocyte Spectrin Head-to-head Tetramer

Head-to-head assembly of two spectrin heterodimers to form an actin-cross-linking tetramer is a physiologically dynamic interaction that contributes to red cell membrane integrity. Recombinant beta-spectrin C-terminal and alpha-spectrin N-terminal peptides can form tetramer-like univalent complexes, but they cannot evaluate effects of the open-closed dimer interactions or lateral associations of the two-spectrin strands on tetramer formation. In this study we produced and characterized a fused "mini-spectrin dimer" containing the beta-spectrin C-terminal region linked to the alpha-spectrin N-terminal region. This fused mini-spectrin mimics structural and functional properties of intact, full-length dimers and tetramers, including lateral association of the alpha and beta subunits in the dimer and formation of a closed dimer. High performance liquid chromatography gel filtration analyses of this mini-spectrin provide the first direct non-imaging experimental evidence for open and closed spectrin dimers and show that dimer-tetramer-oligomer interconversion is slow at low temperatures and accelerated at 30 degrees C, analogous to full-length spectrin. This protein exhibits wild type dimer-tetramer dissociation constants of approximately 1 mum at 30 degrees C, independent of initial oligomeric state. Conformational states of the mini-spectrin dimer were probed further using chemical cross-linking, which identified distinct groups of cross-links for "open" and "closed" dimers and confirmed the N-terminal region of alpha-spectrin remains highly flexible in the complex, exhibiting closely analogous structures to those observed for the isolated alpha-spectrin N-terminal using NMR (Park, S., Caffrey, M. S., Johnson, M. E., and Fung, L. W. (2003) J. Biol. Chem. 278, 21837-21844). This fusion protein should serve as a useful template for structural and functional studies of the divalent tetramer site.

Anion conductance of the human red cell is carried by a maxi-anion channel

Historically, the anion transport through the human red cell membrane has been perceived to be mediated by Band 3, in the two-component concept with the large electroneutral anion exchange accompanied by the conductance proper, which dominated the total membrane conductance. The status of anion channels proper has never been clarified, and the informations obtained by different groups of electrophysiologists are rather badly matched. This study, using the cell-attached configuration of the patch-clamp technique, rationalizes and explains earlier confusing results by demonstrating that the diversity of anionic channel activities recorded in human erythrocytes corresponds to different kinetic modalities of a unique type of maxi-anion channel with multiple conductance levels and probably multiple gating properties and pharmacology, depending on conditions. It demonstrates the role of activator played by serum in the recruitment of multiple new conductance levels showing very complex kinetics and gating properties upon serum addition. These channels, which seem to be dormant under normal physiological conditions, are potentially activable and could confer a far higher anion conductance to the red cell than the ground leak mediated by Band 3.

FY polymorphisms and vivax malaria in inhabitants of Amazonas State, Brazil

Although the importance of glycoprotein Duffy in the human red cells invasion process by Plasmodium vivax merozoites has been demonstrated, little is known about the associations of FY polymorphisms with malaria vivax parasitic density. In this study, we investigated the associations of the SNPs 125 G>A, 265 C>T, and 298 G>A on FY gene and the SNP -33T>C on GATA box with the vivax malaria parasitic density in inhabitants of Amazon State, Brazil. Verifications of P. vivax, as well as the definition of parasitism, were determined by standard screening tests in 497 patients. FY phenotyping was performed in all samples by hemagglutination using gel cards. Molecular analysis for FY/GATA polymorphisms were performed by polymerase chain reaction-restriction fragment length polymorphism. Our data showed that in this population, FY*A/FY*B-33 and FY*B/FY*B-33 genotypes may be a selective advantage, reducing the frequency of P. vivax infection in the studied area. FY*A/FY*B and FY*A/FY*A genotypes showed to be associated with the rise of the frequency of P. vivax infection, and FY*B/FY*X and FY*A/FY*X showed to be associated with the low levels of parasitism. These results suggest that natural adaptations, in malaria-endemic regions, could be leading to the arising of partial defense mechanisms against P. vivax, which is different from the previously described in African descents, as well as adaptations that could be increasing the susceptibility of human to this kind of malaria.

Parallel Reductions in Stomatin and Na,K-ATPase through the Exosomal Pathway during Reticulocyte Maturation in Dogs: Stomatin as a Genotypic and Phenotypic Marker of High K+ and Low K+ Red Cells

Dogs can be divided into two genetic groups (a minor HK phenotype and a major LK phenotype) based on erythrocyte monovalent cation concentrations, which are controlled by the putative hk and lk allelic genes. HK dogs retain Na,K-ATPase in their erythrocytes due to the high activity of the enzyme in their precursor cells, whereas total loss of reticulocyte Na,K-ATPase occurs in LK dogs. Here, we report that the levels of the lipid raft-associated membrane protein stomatin decrease in parallel with those of Na,K-ATPase during reticulocyte maturation due to its extrusion in exosomes. The stomatin content of HK reticulocytes is higher than that of LK reticulocytes, and remains in the erythrocytes at levels compatible with that in human erythrocytes. However, it is almost absent from LK erythrocytes with the lk/lk genotype; similar to the deficiency seen in human red cells with overhydrated stomatocytosis. LK erythrocytes from hk/lk genotype dogs show reduced, but not negligible, levels of stomatin. These results indicate that the erythrocyte stomatin level is a suitable genotypic marker for the HK/LK red cell phenotype, and suggests a functional association between stomatin and Na,K-ATPase. The absence of morphological abnormalities in the erythrocytes of stomatin-deficient LK dogs also confirms that stomatin deficiency and stomatocytic shape change are independent from each other.

Loss of the Gata1 Gene IE Exon Leads to Variant Transcript Expression and the Production of a GATA1 Protein Lacking the N-terminal Domain

GATA1 is essential for the differentiation of erythroid cells and megakaryocytes. The Gata1 gene is composed of multiple untranslated first exons and five common coding exons. The erythroid first exon (IE exon) is important for Gata1 gene expression in hematopoietic lineages. Because previous IE exon knockdown analyses resulted in embryonic lethality, less is understood about the contribution of the IE exon to adult hematopoiesis. Here, we achieved specific deletion of the floxed IE exon in adulthood using an inducible Cre expression system. In this conditional knock-out mouse line, the Gata1 mRNA level was significantly down-regulated in the megakaryocyte lineage, resulting in thrombocytopenia with a marked proliferation of megakaryocytes. By contrast, in the erythroid lineage, Gata1 mRNA was expressed abundantly utilizing alternative first exons. Especially, the IEb/c and newly identified IEd exons were transcribed at a level comparable with that of the IE exon in control mice. Surprisingly, in the IE-null mouse, these transcripts failed to produce full-length GATA1 protein, but instead yielded GATA1 lacking the N-terminal domain inefficiently. With low level expression of the short form of GATA1, IE-null mice showed severe anemia with skewed erythroid maturation. Notably, the hematological phenotypes of adult IE-null mice substantially differ from those observed in mice harboring conditional ablation of the entire Gata1 gene. The present study demonstrates that the IE exon is instrumental to adult erythropoiesis by regulating the proper level of transcription and selecting the correct transcription start site of the Gata1 gene.

The covalent modification of spectrin in red cell membranes by the lipid peroxidation product 4-hydroxy-2-nonenal

Spectrin strengthens the red cell membrane through its direct association with membrane lipids and through protein–protein interactions. Spectrin loss reduces the membrane stability and results in various types of hereditary spherocytosis. However, less is known about acquired spectrin damage. Here, we showed that α- and β-spectrin in human red cells are the primary targets of the lipid peroxidation product 4-hydroxy-2-nonenal (HNE) by immunoblotting and mass spectrometry analyses. The level of HNE adducts in spectrin (particularly α-spectrin) and several other membrane proteins was increased following the HNE treatment of red cell membrane ghosts prepared in the absence of MgATP. In contrast, ghost preparation in the presence of MgATP reduced HNE adduct formation, with preferential β-spectrin modification and increased cross-linking of the HNE-modified spectrins. Exposure of intact red cells to HNE resulted in selective HNE–spectrin adduct formation with a similar preponderance of HNE–β-spectrin modifications. These findings indicate that HNE adduction occurs preferentially in spectrin at the interface between the skeletal proteins and lipid bilayer in red cells and suggest that HNE–spectrin adduct aggregation results in the extrusion of damaged spectrin and membrane lipids under physiological and disease conditions.

Platelets Play a Protective Role in Erythrocytic Stage Malaria Infection.

Abstract MRG-1Mpl-/- mice lack the thrombopoietin receptor (Mpl) and have 10% the platelet mass of normal, isogenic C57BL/6 animals. When infected with the murine malarial parasite, P. chabaudi, C57BL/6 mice survive the infection whereas Mpl-/- mice die. There is a previously, well-documented thrombocytopenia associated with infection by malarial parasites and, in mice, this is co-incidental with a rise in parasitaemia, not the onset of symptoms. We show that murine infected red cells are preferentially bound to platelets. Using the TUNEL staining technique to identify dead or dying cells we show more TUNEL positive cells in C57BL/6 mice than in the thrombocytopenic Mpl-/- mice. Parasites are more likely to be TUNEL positive if their red cell is bound by a platelet or is CD41 positive. This data provided circumstantial evidence that platelet were directly killing malarial parasites within the red cell in the mouse murine model. It was therefore predictable that aspirin should decrease the resistance to malaria and this proved to be the case. The evidence for the protective role of platelets was substantiated by experiments with human platelets and P.falciparum, the lethal human malarial parasite. Unlike the murine malarias, P.falciparum can be grown in culture (with human red cells). The addition of purified human platelets inhibits the growth of P. falciparum. This is associated with an increase in TUNEL-staining of parasites. It is inhibited by most platelet activation inhibitors (aspirin, Prostaglandin E1, sodium nitroprusside, and the P2Y1 antagonist, MRS2179 as well as administration of aspirin to the platelet donor prior to platelet isolation. Interestingly, inhibition of P2Y12 by MRS2395 does not abrogate the growth inhibitory effect of platelets. Again, infected red cells preferentially bind platelets and there is an excellent correlation between the binding of platelets in infected cells and TUNEL positivity of the resident parasite. This data points strongly to the ability of platelets to kill intraerythocytic malarial parasites. In association with the specificity of binding to infected erythrocytes, this provides a further mechanism of innate immunity, mediated by platelets aimed at controlling the growth of malarial parasites. We surmise that its major impact will be early in infection, prior to the onset of significant parasitaemia or thrombocytopenia, at which stage parasite numbers will greatly outnumber platelets and this will not be an effect strategy. DisclosuresNo relevant conflicts of interest to declare.

Abstract 5300: Targeting Ongoing Arterial Thrombosis With Platelet-Specific Microparticles

In the arterial circulation with rapid blood flow, initial platelet adhesion at sites of vascular injury depends on the interaction between the amino terminal domain of platelet glycoprotein Ib (GPIb-NH2) and the A1 domain of von Willebrand Factor (VWF-A1) immobilized onto the vessel wall. Moreover, platelet aggregation responsible for subsequent thrombus growth is mediated by binding of soluble plasma VWF to GPIb on the platelet membrane. Thus, microparticles (MPs) presenting on their surface GPIb-NH2 or VWF-A1 should be capable of homing to sites of ongoing thrombus formation by mimicking platelets either without or with bound VWF, respectively. To test this hypothesis, we coated fluorescent MPs with recombinant VWF-A1 (residues 445–733 of the mature human VWF subunit) or GPIb-NH2 (residues -2–290). Both proteins were expressed as dimers in the attempt to mimic the corresponding native functional conformations. When added to a washed human red cell suspension and perfused over the appropriate substrate (i.e. MPs coated with VWF-A1 over surface-immobilized GPIb-NH2; or vice versa), both kinds of MPs adhered in equal number at shear rate as high as 10,000 s-1. This response was markedly decreased when MPs were coated with VWF-A1 carrying the loss-of-function mutation G561S. In vivo, derivatized MPs were used in mouse models of thrombosis in the carotid and femoral arteries and in the femoral vein in which a thrombogenic lesion was induce by superfusion of ferric chloride or with a pulsed nitrogen laser. Upon injection during the early stages of platelet response to injury, MPs coated with either VWF-A1 or GPIb-NH2 specifically adhered to the lesion, indicating that both GPIb and VWF were present on the surface of the forming thrombus. In contrast, MPs coated with VWF-A1 were remarkably more efficient than those coated with GPIb-NH2 in targeting nearly occluding thrombi, indicating that the surface of the latter presents GPIb (platelets) but not accessible VWF. These findings show that MPs derivatized with specific adhesive domains may be used to target areas of vascular injury with developing thrombi for diagnostic or therapeutic purposes, as well as to interrogate thrombus composition.

Ca-ATPase Activity of Human Red Cell Ghosts: Preeclampsia, Lipid Peroxidation and MgSO4

The increased level of lipid peroxidation of red blood cells during preclampsia is considered to be responsible for the diminished Ca-ATPase activity in these cells. The level of lipid peroxidation and the Ca-ATPase activity of red blood cells from preeclamptic women, return to their normal values after in vivo and in vitro treatment with MgSO4 for 24 h. In order to evaluate whether or not cell intactness is essential for these changes, we used either intact red blood cells or red cell ghosts from normotensive pregnant women. The intact red blood cells were treated with Fenton's reagent and then incubated with 4 mM MgSO4. The red cells ghosts were irradiated with UV light and afterwards incubated with MgSO4 at 4°C. Lipid peroxidation and Ca-ATPase activity were determined for all the preparations. Both, Fenton's reagent and UV irradiation increased the level of lipid peroxidation and diminished the Ca-ATPase activity of the red cell membranes. Incubation of the cells treated with Fenton's reagent, or the ghosts irradiated with UV, with 4 mM MgSO4, returned Ca-ATPase activity and lipid peroxidation levels to normal values. The presence of MgSO4 blocked the effects in the ghosts of UV irradiation. MgSO4 seems to better protect the red cell membrane against lipid peroxidation than other SO4= and Cl− salts. These results indicate that the changes in the lipid peroxidation of the red cell ghosts and their Ca-ATPase activity are a result of changes to the cell membranes.

4.1R-deficient human red blood cells have altered phosphatidylserine exposure pathways and are deficient in CD44 and CD47 glycoproteins

Protein 4.1R is an important component of the red cell membrane skeleton. It imparts structural integrity and has transmembrane signaling roles by direct interactions with transmembrane proteins and other membrane skeletal components, notably p55 and calmodulin. Spontaneous and ligation-induced phosphatidylserine exposure on erythrocytes from two patients with 4.1R deficiency were studied, using CD47 glycoprotein and glycophorin C as ligands. We also looked for protein abnormalities in the 4.1R-based multiprotein complex. Phosphatidylserine exposure was significantly increased in 4.1R-deficient erythrocytes obtained from the two different individuals when ligands to CD47 glycoprotein were bound. Spontaneous phosphatidylserine exposure was normal. 4.1R, glycophorin C and p55 were missing or sharply reduced. Furthermore there was an alteration or deficiency of CD47 glycoprotein and a lack of CD44 glycoprotein. Based on a recent study in 4.1R-deficient mice, we found that there are clear functional differences between interactions of human red cell 4.1R and its murine counterpart. Glycophorin C is known to bind 4.1R, and we have defined previously that it also binds CD47. From our evidence, we suggest that 4.1R plays a role in the phosphatidylserine exposure signaling pathway that is of fundamental importance in red cell turnover. The linkage of CD44 to 4.1R may be relevant to this process.

Babesia divergens Apical Membrane Antigen 1 and Its Interaction with the Human Red Blood Cell

Multiple parasite ligand-erythrocyte receptor interactions must occur for successful Babesia and Plasmodium invasion of the human red cell. One such parasite ligand is the apical membrane antigen 1 (AMA1) which is a conserved apicomplexan protein present in the micronemes and then secreted onto the surface of the merozoite. Much evidence exists for a vital role for AMA1 in host cell invasion; however, its interaction with the host erythrocyte has remained controversial. In this paper, we present a detailed characterization of a Babesia divergens homolog of AMA1 (BdAMA1), and taking advantage of the relatively high amounts of native BdAMA1 available from the parasite culture system, show that proteolytic products of native BdAMA1 bind to a trypsin- and chymotrypsin-sensitive receptor on the red blood cell. Moreover, immuno-electron microscopic images of the B. divergens merozoite captured during invasion offer additional evidence of the presence of BdAMA1 on the red cell membrane. Given the importance of AMA1 in invasion and the central role invasion plays in pathogenesis, these studies have implications both for novel drug design and for the development of new vaccine approaches aimed at interfering with AMA1 function.

Two novel antimicrobial peptides from centipede venoms

Centipede venoms are complex mixtures of biochemically and pharmacologically active components such as peptides and proteins. Very few are known about their pharmacological actions. The present work reports the structural and functional characterization of two antimicrobial peptides (scolopin 1 and -2) identified from centipede venoms of Scolopendra subspinipes mutilans by Sephadex gel filtration and reverse-phase high-performance liquid chromatography (RP-HPLC). The amino acid sequences of scolopin 1 and -2 were FLPKMSTKLRVPYRRGTKDYH and GILKKFMLHRGTKVYKMRTLSKRSH determined by Edman degradation and matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). Both scolopin 1 and -2 showed strong antimicrobial activities against tested microorganisms including Gram-positive/negative bacteria and fungi. They also showed moderate hemolytic activity against both human and rabbit red cells. This is the first report of antimicrobial peptides from centipedes.

Investigation of biomembrane-drug interactions of different biomembranes by capillary electrophoresis

Biomembrane-coated capillaries are prepared by coating different kinds of biomembranes including mice red cell membrane, human red cell membrane and S-180 cell membrane on the inner surface of the capillary, respectively. Effects of immobilized biomembrane amount, pH and biomembrane species on the interactions between drugs and biomembranes have been evaluated. The results showed that the chromatographic retention factor for each drug was essentially related to the amount of immobilized biomembrane, the pH and the type of biomembrane.

Indomethacin activates carbonic anhydrase and antagonizes the effect of the specific carbonic anhydrase inhibitor acetazolamide, by a direct mechanism of action

In this paper we investigated the effect of indomethacin, acetazolamide and their combination in vitro and in vivo on carbonic anhydrase (CA) isozymes. In vitro experiments followed the effect of the two substances at concentrations between 10(-8)-10(-4) M on purified human red cell CA I and II as well as on human gastric mucosa CA IV using dose-response relationships. Kinetic studies were also performed. The effects of single and combined administration of indomethacin and acetazolamide on red cell CA and on gastric acid secretion were studied in vivo. Indomethacin, in vitro and in vivo. induces an increase in erythorcyte CA I and CA II activity. Acetazolamide, a specific inhibitor of CA, reduces the activity of CA I and CA II from red cells. Indomethacin completely antagonizes CA activity, i.e. abolishes the inhibitory effect of acetazolamide on CA. In humans, an increase or decrease in erythrocyte CA II activity is correlated with an increase or decrease in gastric acid secretion. Our results show that indomethacin, a known cyclooxygenase (COX) inhibitor, is also an activator of CA. Our data also prove that indomethacin is not only an activator of CA but also antagonizes the effect of acetazolamide, a specific inhibitor of this enzyme. In view of the role of CA in acid-base balance as well as the fact that an increase or decrease in its activity is accompanied by an increase or decrease in intra- and extracellular pH, our results suggest that: firstly, CA activation induced by indomethacin might cause changes in COX activity; secondly, PGs are synthetized as a consequence of the changes in COX activity, a hypothesis that requires further study.

Mechanical properties of the human red blood cell membrane at −15 °C

The most common method for measuring the mechanical behavior of the human red blood cell (RBC) membrane is micropipette aspiration, because it can be used to apply both a low uniaxial stress at a small part of the membrane or high two-axial stresses to the whole membrane [E.A. Evans, R.E. Waugh, Mechano-chemical study of red cell membrane structure in situ, in: Kroc Foundation Series, vol. 13, Erythrocyte Mechanics and Blood Flow, Alan R. Liss. Inc., New York, 1980, pp. 31–56 (Chapter 3); H.J. Meiselman, Measures of blood rheology and erythrocyte mechanics, in: Kroc Foundation Series, vol. 13, Erythrocyte Mechanics and Blood Flow, Alan R. Liss. Inc., New York, 1980, pp. 75–117 (Chapter 5)]. The elastic shear moduli and area changes of the human RBC published to date were calculated by means of this technique. However, a main drawback of the method is its impracticability at subzero temperatures. Experiments at below 0 °C are of interest because it is at these temperatures that RBC lysis occurs during freezing and thawing after cryopreservation, via a mechanism that may be mechanical. A method for circumventing this limitation is deforming the cell membranes by applying an electric ac field to a supercooled suspension. In a previous study, we applied this technique to human RBCs down to −15 °C [M. Krueger, F. Thom, Deformability and stability of erythrocytes in high-frequency electric fields down to subzero temperatures, Biophys. J. 73 (1997) 2653–2666]. In this technique, the electrical dimensions must be translated into those of mechanics. We provided a formula for these calculations, which demonstrated excellent concordance with known mechanical measurements at room temperature [F. Thom, H. Gollek, Calculation of mechanical properties of human red cells based on electrically induced deformation experiments, J. Electrostat. 64 (2006) 53–61]. Using this formula, we have now calculated the shear moduli and stress–strain diagram for our deformation experiments at −15 °C and present the results below.

Estimation of human red blood cells size using light scattering images

In this paper, a novel method for the estimation of the human Red Blood Cell (RBC) size using light scattering images is presented. The information retrieval process includes, image normalization, ...

Survival of human red cells (RCS) determined using multiple densities of biotin label

Anemia is a serious problem in the neonate. To investigate the pathophysiology of neonatal anemia, to assess responses to blood transfusions and therapy, and to comparatively evaluate various sources of RBC and methods for RBC storage, direct measurement of RCS would be useful.MethodsTo develop a method for simultaneous measurements of RCS, the density of biotin label on RBCs (BioRBC) was incrementally increased to produce 4 distinct BioRBC populations. Following reinfusion, blood was sampled over the next 4 mo, and the decline in BioRBCs was determined by flow cytometric enumeration.ResultsBioRBC at reagent concentrations < 81 μg/mL RBC produced superimposable linear disappearance curves (Fig) and normal survival (mean potential lifespan=117±5 d). BioRBC at 243 µg/mL disappeared rapidly and were not suitable for RCS.ConclusionRCS of distinct populations of infused RBCs in humans can be measured accurately using enumeration of BioRBC. RCS of different blood sources (e.g., placenta, donor, and autologous) can be simultaneously tracked. Supported by NIH P01 HL046925; Thrasher Research Foundation 02825‐3.

Biophysical Characterization And Membrane Interactions Of Peptides With Antimicrobial Potential

It has been estimated that multiresistant bacteria present in hospitals are responsible for 2.5 millions of infections and of several thousands deaths each year in North America. The development of new classes of antibiotics is thus very important to fight against these bacteria. Amphipathic peptides with cationic charges represent one of these new classes. These peptides act by disrupting negatively charged bacterial membranes and have less effect on neutral eukaryotic plasma membrane.We have previously shown that a non-natural peptide composed of 14 non charged residues (10 leucines and 4 phenylalanines modified with a crown ether) is able to disrupt bilayers but without selectivity (1, 2).To gain specificity against negatively charged membranes, several leucines of this 14-mer have been substituted by positively charged residues (lysine, arginine, histidine). Biological tests indicate that some peptides are active against E. coli but ineffective against human red cells. These compounds have thus interesting properties to be use as antibiotics in the future.In our group, we study these peptides by biophysical methods in order to better understand their mode of action on membranes. Fluorescence and Fourier transform infrared spectroscopies studies indicate that selective peptides disrupt negatively charged membranes but have no effect on neutral membranes. These methods, as well as dynamic light scattering and solid-state NMR also suggest that the peptides induce pore formation in the target membranes. This ability is related to the ability of peptides to be mainly in alpha-helix structure.References :1) Y.R. Vandenburg, B.D. Smith, E. Biron, N. Voyer (2002) Chem Commun (Camb). 21:1694-1695.2) M. Ouellet, F. Otis, N. Voyer, M. Auger (2006) Biochim Biophys Acta. 1758:1235-1244.

Decreased erythrocyte glutathione peroxidase activity in multiple sclerosis.

The mean activity of glutathione peroxidase (GSH-PX) in erythrocytes of 22 Israel-Jewish patients with multiple sclerosis (19.3 +/- 4.5 U/gHb) was significantly lower than in a control group of 30 Jewish patients with various neurological disorders (24.3 +/- 5.1 U/gHb). This observation confirms a similar finding of a decreased activity of GSH-Px in erythrocytes of multiple sclerosis patients in Denmark (Shukla et al. 1977). These results are discussed in relation to the possibility of selenium deficiency and to the recently described genetic polymorphism and ethnic variation of GSH-Px activity in human red cells. It is concluded that additional investigations are required in order to elucidate the cause of the decreased activity of this enzyme in red cells of patients with multiple sclerosis.