| Description | Absorbance: A412 nm = 1.10 at 1/50 dilution in deionized waterGeneral DescriptionEr are rabbit red blood cells which have been washed free of rabbit plasmaproteins, but they are not coated with antibodies as is done with EA. These cells have traditionally been used as cells that spontaneously Absorbance: A412 nm = 1.10 at 1/50 dilution in deionized waterGeneral DescriptionEr are rabbit red blood cells which have been washed free of rabbit plasmaproteins, but they are not coated with antibodies as is done with EA. These cells have traditionally been used as cells that spontaneously activate the human alternative complement pathway in serum samples (Morgan, B.P. (2000; Dodds, A.W. and Sim, R.B. (1997)). Most human serum samples have small amounts of natural antibodies (usually IgG) to rabbit antigens and at high concentrations of serum these will agglutinate Er. This will activate the classical pathway if not blocked. Blocking the classical pathway is usually accomplished with 3 to 13 mM MgEGTA.Er are supplied at assay-ready concentrations in the traditional buffer used for APH50 assays (GVB°) which lacks metal ions. They can usually be used for 2 weeks after preparation. They are shipped cold, but are not harmed by extended periods at room temperature (note that they circulate 60+ days at 37℃in vivo). They should be washed once before each use (3-5 min at 500 to 1000 x g at 4℃) and resuspended in GVB° to reduce background and readjust their concentration. This procedure may also be used to concentrate the cells.Physical CharacteristicsEr are natural uncoated (non-opsonized) rabbit erythrocytes.AssaysAlthough the APH50 titer is widely used and serves as the primary test for alternative pathway complement activity, the APH50 assay procedure is not entirely standardized. In research labs there are as many procedures as there are labs, but all are basically similar and give useful results. The main difference between the classical pathway assays for CH50 determination and the alternative pathway assays for APH50 is the concentration of serum required. Alternative pathway activity becomes ineffective at dilutions of serum beyond 1/10 to 1/30. In contrast, CH50 titers are performed in the range 1/100 to 1/500 dilution. Dilution silences the alternative pathway in CH50 titers, but APH50 measurements would be overwhelmed by the classical pathway if this pathway were not blocked. Blocking of alternative pathway activity may be accomplished by using serum depleted of factor B or D or most conveniently by adding 3 to 13 mM MgEGTA (final concentration) to the assays which completely inhibits the classical pathway by chelating calcium ions and dissociating C1. Briefly, a complement-containing serum sample is diluted such that the final dilutions in the assay are in the range from 1/2 to 1/20. Controls include two tubes with no complement for the 0% lysis background and two tubes for 100% lysis. Assay tubes should be set up on ice. The assays are performed in 200 µL containing 4 to 60 µL of test serum, 10 µL 0.1 M MgEGTA, GVB°, and 50 µL Er. The assays are mixed and placed in a 37℃ water bath with remixing at approximately 10 min intervals. After 30 min, 2 mL of cold GVBE is added, mixed and the unlysed cells are spun down (500-1000 x g for 3 min). The absorbance of the supernatant should be determined at 412 nm in a 1 cm cuvette and the percentage of specific lysis calculated after subtracting the background and dividing by the 100% lysis control. The data is plotted as percent lysis on the y axis and µL serum on the x axis. The APH50 value of the complement sample is calculated from the amount of serum needed to cause lysis of 50% of the cells. For example, if it takes 12 µL NHS to lyse 50% of the cells then this serum would contain 83 AHP50 units/mL (1000 µL /12 µL = 83 units/mL). It should be noted that somewhat different APH50 values can be obtained on what should be identical samples. This is the result of the vast number of variables involved in APH50 determinations including the fact that each batch of rabbit erythrocytes is slightly different.ApplicationsEr cells are primarily used to determine the activity of the alternative pathway of complement (APH50 titer) (Morgan, B.P. (2000; Dodds, A.W. and Sim, R.B. (1997)). Natural antibodies present in human blood to animal antigens may cause agglutination of the cells. This antibody may also cause lysis if the classical pathway is not blocked.Rabbit erythrocytes are attacked and lysed by the alternative pathways of most mammalian species. It has not been clearly demonstrated why rabbit complement does not lyse rabbit Er when most other animal species do lyse these cells, although they do carry rabbit DAF which works on rabbit, but not human complement enzymes.RegulationRabbit erythrocytes (Er) are used for human complement assays partly for convenience, but also because they lack membrane-bound regulators of human complement. No significant level of functional DAF, CD59 or CR1 exists on Er for human complement. Thus, Er are useful for their lack of membrane regulatory activities... Read More | Inquire | Protein Purity>90 % by SDS PAGEExtinction CoeffA280 nm = 0.725 at 1.0 mg/mL for pure C1s-C1INH ComplexMolecular Weight196,000 Da (1 chain)General DescriptionThe product C1s-C1INH Complex is made by interacting purified protease inhibitor C1-INH with purified C1s enzyme followed by purification. Protein Purity>90 % by SDS PAGEExtinction CoeffA280 nm = 0.725 at 1.0 mg/mL for pure C1s-C1INH ComplexMolecular Weight196,000 Da (1 chain)General DescriptionThe product C1s-C1INH Complex is made by interacting purified protease inhibitor C1-INH with purified C1s enzyme followed by purification. The protease inhibitor C1-INH prevents the spontaneous activation of complement and limits consumption of C2 and C4 by rapidly inactivating C1r, C1s and MASP2. It is the only plasma serine protease inhibitor (Serpin) capable of interacting with and inhibiting activated C1. C1-INH interacts with the catalytic sites of both C1r and C1s. The interaction with activated C1r and C1s is covalent resulting in complexes which are stable to SDS. C1s and C1r enzymes, however, are irreversibly inactivated by binding to C1-INH. C1s-C1INH is a very stable complex that remains intact even when subjected to freeze/thaw cycles with almost no loss of the complex form.Physical Characteristics & StructureThe C1s enzyme-C1INH complex is composed of two disulfide linked chains from C1s enzyme (A chain 58,000 Da and B chain 28,000 Da) and one covalently linked chain from C1-INH (75,000 Da).SDS-PAGE analysis of the C1s-C1INH complex shows a single band of about 161,000 Da under nonreducing conditions. Under reducing conditions, the C1s-C1INH complex exhibits two bands: A 58,000 Da band corresponding to the A chain of C1s enzyme and a second 103,000 Da band resulting from C1INH (75,000 Da) covalently bond to the B chain (28,000 Da) of C1s enzyme.RegulationActivated C1s is controlled by C1-INH. C1s enzyme and C1-INH form a covalent complex that is resistant to separation on SDS gels. During complement activation C1 complex is rapidly activated by binding to immune complexes. The resulting activated C1s and C1r are rapidly inactivated by interaction with C1-INH (Ziccardi, R.J. (1982)). Binding to immune complexes is fast (10-20 sec) and activation of the bound C1 complex takes several minutes, but C1-INH has also been shown to be fast and no active C1r or C1s remain 4 min after addition of immune complexes to plasma (Ross, G.D. (1986); Ziccardi,R.J. (1981)). The binding of C1-INH to activated C1 releases both C1r and C1s from the complex leaving C1q bound to the immune complex. The released complexes contain four molecules: C1-INH-C1r-C1s-C1-INH. The reaction of C1 esterase inhibitor with activated C1 is very fast with the estimated half-life of C1r and C1s being approximately 15 seconds in serum. In fact, at serum concentrations of C1- INH little or no additional C4 or C2 activation occurs 3 min after immune complexes are added because all the C1r and C1s molecules have been inactivated and removed from the C1q which remains bound to the immune complex (Ross, G.D. (1986); Morley, B.J. and Walport, M.J. (2000); Rother, K., et al. (1998); Ziccardi, R.J. (1982a and 1982b); Morgan, B.P. (1990)). The interaction of purified C1s enzyme and C1-INH is slower.FunctionSee General Description and Regulation above.ApplicationsC1s-C1INH complex can be used in studies designed for developing and identifying inhibitors of C1s-C1INH complex formation and thus lead to the possible development of therapeutics for inhibiting complement activation via the classical pathway.GeneticsThe EMBL/Genbank cDNA accession number for C1s is J04080. The gene for C1s is located on chromosome 12p13. The EMBL/Genbank cDNA accession numbers for C1-INH are M13656 and X54486 (human) and Y10386 (mouse). The gene for C1-INH is located on chromosome 11p11.2-13. DeficienciesC1s deficient patients are prone to systemic lupus erythematosus (SLE) and recurrent pyogenic infections (Rother, K., et al. (1998)). They lack classical pathway function. The genetic disorder hereditary angioedema (HAE) is caused by a partial deficiency of C1-INH. Patients with HAE have low functional C1-INH levels in blood and have recurrent episodes of systemic or localized edema.DiseasesSee section titled Deficiencies above. Precautions/Toxicity/HazardsThis protein is purified from human serum and therefore precautions appropriate for handling any blood-derived product must be used even though the source was shown by certified tests to be negative for HBsAg, HTLV-I/II, STS, and for antibodies to HCV, HIV-1 and HIV-II.ReferencesZiccardi, RJ. (1982) A new role for C-1-inhibitor in homeostasis: control of activation of the first component of human complement. J. Immunol. 128:2505-2508.Ross, G.D. (1986) Immunobiology of the Complement System. (ISBN 0-12-5976402) Academic Press, Orlando.Ziccardi, R.J. (1981) Activation of the early components of the classical complement pathway under physiologic conditions. J. Immunol. 126:1769-1773.Morley, B.J. and Walport, M.J. (2000) The Complement Facts Book. (ISBN 0127333606) Academic Press, London.Rother, K., Till, G.O., and Hӓnsch, G.M. (1998) The Complement System. (ISBN 3-540- 61894-5) Springer-Verlag, Heidelberg.Ziccardi, R.J. (1982a) Spontaneous activation of the first component of human complement (C1) by an intramolecular autocatalytic mechanism. J. Immunol. 128:2500- 2504.Ziccardi, RJ. (1982b) A new role for C-1-inhibitor in homeostasis: control of activation of the first component of human complement. J. Immunol. 128:2505-2508. Morgan, B.P. (1990) Complement Clinical Aspects and Relevance to Disease. (ISBN 0- 12-506955-3) Academic Press, London... Read More | Purity: >90%, by SDS-PAGE visualized with Coomassie® Blue Staining.Description：Involved in the high-affinity maltose membrane transport system MalEFGK. Initial receptor for the active transport of and chemotaxis toward maltooligosaccharides.Epitope tagging offers an easy and universalPurity: >90%, by SDS-PAGE visualized with Coomassie® Blue Staining.Description：Involved in the high-affinity maltose membrane transport system MalEFGK. Initial receptor for the active transport of and chemotaxis toward maltooligosaccharides.Epitope tagging offers an easy and universal strategy for the identification and purification of proteins derived by recombinant DNA technology. The insertion of a Maltose Binding Protein (MBP) tag creates a stable fusion product that does not interfere with the bioactivity of the protein or with the biodistribution of the MBP tagged product... Read More | Reverse transcriptases are enzymes encoded in retroviruses viral genome. The enzyme is responsible for transcription of the viral RNA to produce a dsDNA that can be inserted into the host genome.Reverse transcriptases are multifunctional enzymes. These enzymes exhibit an RNA and DNA directed Reverse transcriptases are enzymes encoded in retroviruses viral genome. The enzyme is responsible for transcription of the viral RNA to produce a dsDNA that can be inserted into the host genome.Reverse transcriptases are multifunctional enzymes. These enzymes exhibit an RNA and DNA directed polymerase activity. In addition reverse transcriptases catalyze the degradation of RNA in an RNA-DNA hybrid. The exonucleolytic activity proceeds in a 5' ---> 3' direction. The RNA or DNA directed activity requires a template (RNA or DNA) and a primer. The following is a schematic illustration of the reaction:Unit definition: One unit incorporates 1 nanomole of tritiated dTMP into acid insoluble productsusing poly(A)•oligo(dT) 12-18 as the template-primer in 20 minutes at 37° C.ApplicationsHIV reverse transcriptase is used for research on the AIDS primer. However it can be substituted for AMV reverse transcriptase, which is mainly used to transcribe mRNA into double stranded cDNA, that can be inserted into prokaryotic vectors. The enzyme can also be used with either single stranded DNA or RNA templates to make probes for use in hybridization experiments. It can be used for labeling the termini of DNA fragments with protruding 5' termini. The enzyme can also be used to sequence DNAs by the dideoxy chain termination method of Sanger when the Klenow fragment of E. coli DNA polymerase I, or the T7 DNA polymerase yield unsatisfactory results.Reagents0.05 M Tris, pH 8.3, containing 0.008 M MgCl21 mg/ml polyadenylic acid in water (poly A)DNA primer:Oligo d(T)12-181 µ mole dTTP/mL stock solution[methyl-3H]-Thymidine 5'-triphosphate (3H-dTTP)dTTP-3H-dTTP working mix: Add 1-2 µL 3H-dTTP per mL of 100 nmol/mL dTTP in order to obtain 1 to 1.5 x 105 cpm/mL1% bovine serum albumin10% perchloric acid1% perchloric acidBuffer substrate reaction mixture: Prepare fresh, immediately before use:For each 1mL of reaction mixture required mix:0.7 mL Tris/HCl, pH 8.3, 0.008M MgCl20.3 mL 1 mg/mL poly(A) RNA template0.005 mL 0.02 mg/mL oligo d(T)12-18 DNA primer0.02mL 1% BSAEnzymedilute as needed wtih 0.05M Tris/HCl, pH 8.3, 0.008M MgCl2 containing 0.1 mg/mL (1%) BSAProcedurePipette into each tube as follows:Buffer substrate mix：0.1 mLdTTP-3H3-dTTP：0.1 mLEnzyme：5-10 µLIncubate 20 minutes at 37° C. Stop reaction by adding 1 ml 10% cold perchloric acid. Filter through 0.2µ manifold filters used with Millipore vacuum manifold. Wash four times using 2mL 1% cold perchloric acid/wash. Transfer filter to scintillation vials. Add 2mL Cellosolve (or 2-methoxyethanol) to dissolve filter. Filters become opaque upon addition of Cellosolve. Make sure filters are dissolved before proceeding. Add 10mL scintillation cocktail and count.Calculation... Read More |