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At least 19 recordsLinked to original sources

PubMed1991

Copper(II) (3,5-diisopropylsalicylate)2 oxidizes thiols to symmetrical disulfides and oxidatively converts mixtures of 5-thio-2-nitrobenzoic acid and nonsymmetrical 5-thio-2-nitrobenzoic acid disulfides to symmetrical disulfides.

L-cysteine, D-penicillamine, and L-glutathione were oxidized to symmetrical disulfides in the presence of Cu(II)(3,5-DIPS)2 and air-oxygen at physiologic pH, 7.3. Air-oxygen caused the oxidation of thiol reduced copper, Cu(I), to Cu(II), as evidenced by expected spectrophotometric changes in these reaction mixtures. L-cysteine, D-penicillamine, and L-glutathione formed mixed disulfides and TNB with the addition of DTNB to solutions of these thiols. The observed order of reactivity for these thiols with DTNB was: L-cysteine greater than D-penicillamine greater than L-glutathione. Surprisingly, Cu(II)(3,5-DIPS)2 converted these mixed disulfides to their symmetrical disulfides and DTNB, and although the initial conversion rate was rapid, complete conversion required more than two hours. These observations suggest caution with regard to the spectrophotometric determination of thiols immediately after the addition of Ellman's reagent. These results also clarify an earlier report concerning the oxidation of thiols by Cu(II)(o-phenanthroline)2 and offer caution with regard to the determination of thiols using DTNB in the presence of copper complexes. Spectrophotometric data are provided in support of the suggestion that analysis of plasma or cellular samples for thiols be done in the absence of copper(II) complexes to avoid false negative results.

Cysteine↗

PubMed1977

Identification of a coenzyme A--glutathione disulfide (DSI), a modified coenzyme A disulfide (DSII), and a NADPH-dependent coenzyme A--glutathione disulfide reductase in E. coli.

The nucleotides DSI and DSII induced during a slowdown in growth of E. coli have been characterized using chemical and biochemical analysis and by enzymic and alkaline fragmentation. DSI consists a coenzyme A and glutathione joined by a disulfide linkage. DSI could be isolated either containing Fe(III) with an A250:260 ratio of 1.05 or not containing iron with an A250:260 of 0.87. DSII (isolated in 10% the yield of DSI) is a coenzyme A disulfide dimer that also contains two molecules of glutamic acid. DSI was a substrate for NADPH-dependent CoAS-SG reductase (EC 1.6.4.6) which was present in crude extracts of E. coli. The specific activity of CoAS-SG reductase increased during growth from early log phase into stationary phase and during a shift from aerobic to anaerobic growth.

Coenzyme A↗

PubMed1992

Disulfide bond-coupled folding of bovine pancreatic trypsin inhibitor derivatives missing one or two disulfide bonds.

The disulfide bond-coupled folding and unfolding mechanism (at pH 8.7, 25 degrees C in the presence of oxidized and reduced dithiothreitol) was determined for a bovine pancreatic trypsin inhibitor mutant in which cysteines 30 and 51 were replaced with alanines so that only two disulfides, between cysteines 14 and 38 and cysteines 5 and 55, remain. Similar studies were made on a chemically-modified derivative of the mutant retaining only the 5-55 disulfide. The preferred unfolding mechanism for the Ala30/Ala51 mutant begins with reduction of the 14-38 disulfide. An intramolecular rearrangement via thiol-disulfide exchange, involving the 5-55 disulfide and cysteines 14 and/or 38, then occurs. At least five of six possible one-disulfide bond species accumulate during unfolding. Finally, the disulfide of one or more of the one-disulfide bond intermediates (excluding that with the 5-55 disulfide) is reduced giving unfolded protein. The folding mechanism seems to be the reverse of the unfolding mechanism; the observed folding and unfolding reactions are consistent with a single kinetic scheme. The rate constant for the rate-limiting intramolecular folding step--rearrangements of other one-disulfide bond species to the 5-55 disulfide intermediate--seems to depend primarily on the number of amino acids separating cysteines 5 and 55 in the unfolded chain. The energetics and kinetics of the mutant's folding mechanism are compared to those of wild-type protein [Creighton, T. E., & Goldenberg, D. P. (1984) J. Mol. Biol. 179, 497] and a mutant missing the 14-38 disulfide [Goldenberg, D. P. (1988) Biochemistry 27, 2481]. The most striking effects are destabilization of the native structure and a large increase in the rate of unfolding.

Alanine↗

PubMedDate not supplied

Disulfide-linked and non-disulfide-linked gamma/delta T-cell antigen receptors: differential expression on T-cell lines and clones derived from normal donors and patients with primary immunodeficiency disorders.

We studied the expression of gamma delta T cell receptors (TCR) on T-cell lines and clones derived from peripheral blood lymphocytes (PBL) from certain patients with primary immunodeficiency disorders and normal donors. Immunoprecipitation with the anti-Leu 4, anti-gamma-chain and/or anti-delta-chain monoclonal antibodies followed by SDS-PAGE analysis revealed that 7 of 13 (54%) T-cell lines and clones developed from PBL of patients with primary immunodeficiency disorders expressed non-disulfide-linked gamma delta TCR, utilizing either the C gamma 2abc or the C gamma 2bc gamma-chain constant region gene segment. 5 of 13 (38%) T-cell lines/clones expressed disulfide-linked gamma delta TCR, whereas an additional T-cell line was comprised of T cells expressing either disulfide-linked (C gamma 1) or non-disulfide-linked (C gamma 2bc) gamma delta TCR. T-cell lines and clones developed from four of light patients with primary immunodeficiency disorders exhibited exclusively non-disulfide-linked gamma delta TCR utilizing either the C gamma 2abc or the C gamma 2bc gamma-chain segment. T-cell lines derived from a fifth patient exhibited primarily non-disulfide-linked gamma delta TCR, bringing to five of eight the numbers of patients that expressed exclusively or primarily non-disulfide-linked gamma delta TCR. T-cell lines/clones derived from the remaining three patients exhibited exclusively disulfide-linked gamma delta TCR. The age of these patients varied over a wide range and there was not an association between their age and the type of gamma delta TCR expressed on T-cell lines derived from their PBL. In contrast, to these findings 14 of 16 (87.5%) T-cell clones derived from PBL of normal donors expressed disulfide-linked gamma delta TCR, whereas only 2 of 16 (12.5% expressed non-disulfide linked gamma delta TCR. Among the T-cell clones from normal donors which express disulfide-linked gamma delta TCR two different types were identified. Those exhibiting under reducing conditions on SDS-PAGE two completely resolved polypeptide chains in the range of 37 kD to 44 kD, and those exhibiting under the same conditions indistinguishable overlapping gamma- and delta- chains in the range of 40-42 kD. Several T-cell lines and clones from normal donors or patients with primary immunodeficiency that expressed either disulfide- or non-disulfide-linked gamma delta TCR were delta TCS1+, demonstrating that the delta TCS1 determinant is expressed on both types of gamma delta TCR.(ABSTRACT TRUNCATED AT 400 WORDS)

Antigens, CD↗

PubMed1990

Kinetics of disulfide bond reduction in alpha-lactalbumin by dithiothreitol and molecular basis of superreactivity of the Cys6-Cys120 disulfide bond.

Kinetics of disulfide reduction in alpha-lactalbumin by dithiothreitol are investigated by measuring time-dependent changes in absorption at 310 nm and in CD ellipticity at 270 nm (pH 8.5 or 7.0, and 25 degrees C). When the disulfide-intact protein is folded, the kinetics are biphasic. The disulfide bond between the half-cystines-6 and -120 is reduced in the fast phase, and the other three disulfide bonds are reduced in the slow phase. The apparent rate constants of the two phases are both proportional to the concentration of dithiothreitol, indicating that both phases are expressed by bimolecular reactions. However, detailed molecular mechanisms that determine the reaction rates are markedly different between the two phases. The slow phase shows a sigmoidal increase in the reaction rate with increasing concentration of a denaturant, urea, and is also accelerated by destabilization of the native state on removal of the bound Ca2+ ion in the protein. The disulfide bonds are apparently protected against the reducing agent in the native structure. The fast phase reaction rate is, however, decreased with an increase in the concentration of urea, and the disulfide bond shows extraordinary superreactivity in native conditions. It is 140 times more reactive than normal disulfides in the fully accessible state, and three-disulfide alpha-lactalbumin produced by the fast phase assumes nativelike structure under a strongly native condition. As ionic strength does not affect the superreactivity of this disulfide bond, electrostatic contributions to the reactivity must be negligible. Inspection of the disulfide bond geometry based on the refined X-ray coordinates of baboon alpha-lactalbumin [Acharya et al. (1989) J. Mol. Biol. 208, 99-127] and comparison of the geometry with those in five other proteins clearly demonstrate that the superreactivity arises from the geometric strain imposed on this disulfide bond by the native structure folding. Relationships of the disulfide strain energy to the protein stability and the disulfide reactivity are discussed.

Chemical Phenomena↗

PubMed1987

Reversibility of disulfide formation. Comparison of chemical and enzyme-mediated reduction of penicillamine and captopril disulfides.

The reduction of penicillamine disulfide by reductants in aqueous solutions has been studied and compared with that for captopril disulfide. Whereas near quantitative reduction for captopril disulfide was achieved with tributyl phosphine (200 mM), no detectable penicillamine was formed from penicillamine disulfide. Thiol reductants (25 mM) were, however, partially able to reduce penicillamine disulfide with the most effective agent being glutathione (15% reduction) following by dithioerythritol (8%) and cysteine (5.1%). The reduction of penicillamine-cysteine disulfide by glutathione was 6-fold higher than for penicillamine disulfide. Kinetic analysis showed that the initial rate of reduction and equilibrium constant for the reduction of penicillamine disulfides by glutathione were 267- and 875-fold less than for captopril disulfide at pH 7.4. Biotransformation studies in the cytosol fraction of rat blood cells demonstrated that whereas 48% of the reduction of captopril disulfide was enzyme-mediated only 19% of the penicillamine formed was enzyme-mediated for penicillamine disulfide. Accumulation of disulfides of penicillamine in patients taking penicillamine may therefore be a problem during chronic therapy.

Animals↗

PubMed1989

Catalysis of thiol/disulfide exchange: single-turnover reduction of protein disulfide-isomerase by glutathione and catalysis of peptide disulfide reduction.

Protein disulfide-isomerase, a protein localized to the lumen of the endoplasmic reticulum of eukaryotic cells, catalyzes the posttranslational formation and rearrangement of protein disulfide bonds. As isolated from bovine liver, the enzyme contains 0.8 free sulfhydryl group per mole of protein monomer and 3.1 disulfide bonds. Single-turnover experiments in which the disulfide bonds of the native enzyme are reduced by glutathione reveal three distinct reduction steps corresponding to the sequential reduction of the three disulfide bonds. The fastest disulfide to be reduced undergoes a change in the rate-determining step with increasing GSH concentration from a step which is second-order with respect to GSH concentration to a step which is first-order in GSH concentration. The disulfide which is reduced at an intermediate rate displays kinetics that are first-order in GSH concentration, and the slowest disulfide to be reduced exhibits kinetics which are second-order in GSH concentration. The enzyme catalyzes the steady-state reduction of a disulfide-containing hexapeptide (CYIQNC) by GSH. Initial velocity kinetic experiments are consistent with a sequential addition of the substrates to the enzyme. Saturation behavior is not observed at high levels of both substrates (Km for GSH much greater than 14 mM, Km for CYIQNC much greater than 1 mM). Only one of the three disulfides appears to be kinetically competent in the steady-state reduction of CYIQNC by GSH. The second-order thiol/disulfide exchange reactions catalyzed by the enzyme are 400-6000-fold faster than the corresponding uncatalyzed reactions.

Catalysis↗

PubMed1987

Experimental human exposure to carbon disulfide. I. Respiratory uptake and elimination of carbon disulfide under rest and physical exercise.

Six human volunteers were exposed to 10 and 20 ppm carbon disulfide at rest and to 3 and 10 ppm carbon disulfide under a 50 W level of physical exercise during four consecutive periods of 50 min. Every 5 min a sample was taken from the mixed exhaled air in which the concentration of carbon disulfide was determined. It was established that only an apparent steady state was reached during this exposure period. The retention values were established as 0.374 (SD = 0.106; n = 239) for exposure to 10 ppm carbon disulfide at rest and as 0.410 (SD = 0.103; n = 239) for exposure to 20 ppm carbon disulfide at rest. During exposure to 10 ppm and 3 ppm carbon disulfide, combined with a 50 W level of physical exercise, the retention values decreased to 0.286 (SD = 0.083; n = 239) and 0.277 (SD = 0.049; n = 239) respectively. Thereby, the measured individual retention values of carbon disulfide show considerable interindividual differences. The respiratory uptake of carbon disulfide (mg CS2) proved significantly influenced by the amount of body fat estimated from skinfold thickness measurements. The respiratory elimination of carbon disulfide in the exhaled air can be described by means of a two-exponential decay.

Adult↗

PubMed1985

Peptide mapping of bovine pancreatic ribonuclease A by reverse-phase high-performance liquid chromatography. II. A two-dimensional technique for determination of disulfide pairings using a continuous-flow disulfide-detection system.

A procedure, developed for the cleavage and reversible blocking of disulfide bonds of proteins by S-sulfonation in preparation for peptide mapping, was applied to ribonuclease A. The complete peptide maps of sulforibonuclease A using limited Staphylococcus aureus protease digestion, tryptic digestion, and tryptic followed by chymotryptic digestion are presented. A description is given of an adaptation of the sulfonation procedure which forms the basis of a sensitive (5-pmol detection limit) and quantitative (+/- 5%) disulfide-detection system for the continuous monitoring of HPLC column effluents for disulfide-containing compounds. The sulfonation procedure, peptide maps, and disulfide-detection system are the key ingredients in a two-dimensional reverse-phase HPLC technique for the determination of disulfide pairings. The applicability of this technique is demonstrated by determining the known disulfide pairings of ribonuclease A. It is also shown that there is no disulfide interchange under the digestion conditions used. This technique is suitable for determining the distributions of disulfide pairings in the intermediates present in the oxidative folding of disulfide-containing proteins.

Animals↗

PubMed1978

Formation of interchain disulfide bonds in Bence Jones proteins and Fab(t) fragments of immunoglobulin G through thiol-disulfide interchange.

The formation of interchain disulfide bonds from partially reduced Bence Jones protein (Nag, type lambda) and Fab(t) fragments of IgG1 myeloma proteins was studied in the presence of various disulfide reagents. The results could be well explained in terms of the scheme proposed previously (Kishida et al. (1976) J. Biochem. 79, 91-105). In this scheme, it was assumed that two kinds of intermediate, which form mixed disulfides with either of the paired thiol groups, are produced. For type lambda Bence Jones proteins, only one of the two intermediates can form the inter L-L disulfide bond. The fraction of intermediate having the ability to form the inter L-L disulfide bond was estimated to be 72% of the total Nag protein and was the same irrespective of the kind of disulfide reagent examined. For Fab(t), on the other hand, both intermediates equally can form the inter Fd-L disulfide bond. On the basis of the results with cystamine, it was shown that the formation of an inter Fd-L disulfide bond from the intermediate proceeds about 100 times as rapidly as that of an inter L-L disulfide bond.

Bence Jones Protein↗

PubMed1987

Interchain disulfide bond formation in types I and II procollagen. Evidence for a protein disulfide isomerase catalyzing bond formation.

The assembly of reduced pro-alpha chains of type I and type II procollagen into the native triple-helical molecule was examined in vitro in the presence and absence of pure protein disulfide isomerase. The data clearly indicates that protein disulfide isomerase is able to accelerate the formation of native interchain disulfide bonds in these procollagens. It takes about 6 min after disulfide bonding before triple-helical molecules exist, while the time required to produce triple-helical type I procollagen in the presence of protein disulfide isomerase is 9.4 min and that for type II procollagen 17.2 min. These values agree with those obtained for type I and II procollagen in vivo suggesting that protein disulfide isomerase is also an enzyme catalyzing interchain disulfide bond formation in procollagen in vivo. The formation of native disulfide bonds can proceed without any enzyme catalysis but then requires the presence of reduced and oxidized glutathione. Bonding is rather slow in such a case, however, resulting in a delay in the formation of the triple helix.

Animals↗

PubMed1989

Determination of penicillamine, penicillamine disulfide and penicillamine-glutathione mixed disulfide by high-performance liquid chromatography with electrochemical detection.

Methodology is described for the simultaneous determination of D-penicillamine, penicillamine disulfide and the penicillamine-glutathione mixed disulfide, as well as glutathione and glutathione disulfide, in human plasma, erythrocytes and urine. The various thiols and disulfides are separated by reversed-phase ion-pairing liquid chromatography with detection by an electrochemical detector with dual gold/mercury amalgam electrodes in series. The thiols are detected at the downstream electrode; the disulfides are reduced at the upstream electrode and then detected as the thiols at the downstream electrode. Detection limits (at a signal-to-noise ratio of 2.0) are in the picomole range for 20 microliters of injected solution for all compounds except penicillamine disulfide, which has a detection limit of 600 pmol in 20 microliters. A convenient method is described for preparation of the penicillamine-glutathione mixed disulfide by thiol/disulfide exchange with standardization of the solution by 1H NMR spectroscopy.

Chromatography, High Pressure Liquid↗

PubMed1977

Biologically oriented organic sulfur chemistry. 15. Organic disulfides and related substances. 41. Inhibition of the fungal pathogen Histoplasma capsulatum by some organic disulfides.

In an extension of promising inhibitory results in vitro against Histoplasma capsulatum, correlated earlier using substituent constants developed by regression analysis with 77 disulfides, one symmetrical and 14 unsymmetrical disulfides were prepared (3--17). About half were active in vitro against H. capsulatum (and one against Candida albicans). Groups that seemed most to lead to promising inhibition among the unsymmetrical disulfides were o-HO2CC6H4, (CH2)4SO2Na, Me2NC(S), p-ClC6H4, and perhaps p-CH3C6H4; the first two also might be used to increase solubility. Earlier inhibitory promise of the morpholino group did not materialize. None of the group 3--17 was significantly active in vivo. The unsymmetrical disulfides were prepared by reaction of thiols with sulfenyl chlorides or with acyclic or cyclic thiosulfonates. Two six-membered heterocyclic disulfides (5 and 6) were prepared by a novel cyclization, in which carbon disulfide reacted with an (N-alkylamino)ethyl Bunte salt, followed by ring closure; an explanation is suggested for formation of a thiazoline when the N-alkyl group is absent. One of the disulfides disproportionated with astonishing ease (31; 0.3--1 h at 25 degrees C).

Amphotericin B↗

PubMed1989

Expression of disulfide-linked and non-disulfide-linked forms of the T cell receptor gamma/delta heterodimer in human intestinal intraepithelial lymphocytes.

Immunohistochemistry has been used to investigate disulfide- and non-disulfide-linked forms of the T cell receptor gamma/delta heterodimer (TcR gamma/delta) in blood and intestinal epithelium of normal human small intestine, intestine of patients with untreated coeliac disease (in whom T cells expressing TcR gamma/delta are disproportionately raised), intestine of patients with tropical malabsorption, and in the human fetus. In blood from adult volunteers, 90% of T cells expressing TcR gamma/delta use the disulfide-linked form. In contrast in the epithelium in normal small intestine, coeliac disease and tropical malabsorption, most of the T cells expressing TcR gamma/delta use the non-disulfide-linked form. This is especially prominent in untreated coeliac disease where the increase in TcR gamma/delta T cells is mainly restricted to those using the non-disulfide-linked form. In human fetal small intestinal epithelium, however, only cells using the disulfide-linked form are present. These variations in expression of different forms of TcR gamma/delta in the gut epithelium in different conditions suggests that antigen, or some as yet undefined factor may determine the frequency of each subpopulation.

Antibodies, Monoclonal↗

PubMed1986

Thiol-disulfide exchange by thrombospondin: evidence for a thiol and a disulfide bond protected by calcium.

Thrombospondin (Tsp), a protein secreted by activated platelets, forms disulfide-linked complexes with thrombin [K. J. Danishefsky, R. J. Alexander and T. C. Detwiler (1984) Biochemistry 23, 4984]. Thiols and disulfide bonds of Tsp were analyzed, and a search was made for other Tsp covalent complexes. Platelets in 1 mM EDTA were activated with ionophore A23187, and the secreted proteins were analyzed by gel electrophoresis in sodium dodecyl sulfate. One millimolar dithioerythritol (DTE) decreased the electrophoretic mobility of Tsp, indicating reduction of an intrachain disulfide bond; Ca2+ prevented this effect. Electrophoresis of single-chain Tsp prepared with 50 mM DTE in either EDTA or Ca2+ also revealed a Ca2+-stabilized intrachain disulfide bond. Ca2+ prevented the retention of Tsp on an activated thiol-Sepharose column, indicating protection of a thiol by Ca2+. Incubation at 37 degrees C for 60 min resulted in complexes with apparent mass much greater than 500 kDa. Formation of complexes was prevented by N-ethylmaleimide, by a temperature less than 25 degrees C, and by Ca2+ or Mg2+. From pH 6 to 9, complexes formed better at lower pH. Two-dimensional (nonreduced/reduced) electrophoresis revealed Tsp but no other constituents of the complexes. With 10 nM thrombin, complexes formed faster and included thrombin; Ca2+ only partially inhibited. The complex was very susceptible to dissociation by low concentrations (2.5 mM) of DTE. It is concluded that Tsp has a reactive thiol and an intrachain disulfide bond that are protected by Ca2+. When these groups are unprotected, there is intermolecular thiol-disulfide exchange.

Blood Platelets↗

PubMed1979

Disulfide-disulfide interchange catalyzed by a liver supernatant enzyme.

An enzyme widely distributed in rabbit tissues which catalyzes an interchange between N,N-di-dinitrophenyl-L-cystine and oxidized glutathione to form the mixed disulfide is described. D-Penicillamine disulfide can be substituted for oxidized glutathione and the mixed disulfide of cysteine and glutathione can serve as the sole substrate giving as one product of interchange, oxidized glutathione. The enzyme is very labile and only limited purification of it has been achieved. The activity increases with increasing pH above 6.6, the Km for N,N-di-dinitrophenyl-L-cystine is 0.2 mM and for oxidized glutathione 0.8 mM. The enzyme is inhibited by SH reagents with protection against iodoacetamide inactivation provided by N,N-di-dinitrophenyl-L-cystine. Evidence is presented that disulfide-disulfide interchange enzyme is a different activity from the previously described protein disulfide isomerase and thiol transferase.

Animals↗

PubMed1989

The position of the disulfide bonds in human plasma alpha 2 HS-glycoprotein and the repeating double disulfide bonds in the domain structure.

The positions of the inter- and intra-chain disulfide bonds of human plasma alpha 2 HS-glycoprotein were determined. alpha 2 HS-glycoprotein was digested with acid proteinase and then with thermolysin. The disulfide bonds containing peptides were separated by reversed-phase HPLC and detected by SBD-F (7-fluorobenzo-2-oxa-1,3-diasole-4-sulfonic acid ammonium salt) method. One inter-disulfide bond containing peptide and five intra-disulfide bond containing peptides (A-chain) were purified and identified as Cys-18 (B-chain)--Cys-14 (A-chain), Cys-71--Cys-82, Cys-96--Cys-114, Cys-128--Cys-131, Cys-190--Cys-201 and Cys-212--Cys-229, respectively. The location of the intra-disulfide bonds revealed that the A-chain of alpha 2 HS-glycoprotein is composed of three domains. Two domains were shown to possess intramolecular homology judging from the total chain length of the domains, size of the loops formed by the S--S bonds, the location of two disulfide loops near the C-terminal end of domains A and B, the distance between two S--S bonds of each domain, the amino acid sequence homology between these two domains (22.6%), number of amino acid residues between the second S--S loops and the end of domains A and B, and the positions of the ordered structures.

Amino Acid Sequence↗

PubMed1976

Enzyme reduction of disulfide bonds by thioredoxin. The reactivity of disulfide bonds in human choriogonadotropin and its subunits.

The NADPH-dependent enzymic reduction of disulfide bonds in human choriogonadotropin and its two subunits, alpha and beta, was examined with thioredoxin and thioredoxin reductase from Escherichia coli. With 12 muM thioredoxin and 0.1 muM thioredoxin reductase at pH 7 all disulfide bonds in the alpha subunit could be reduced in 15 min. The reduction of disulfide bonds was recorded by a simple spectrophotometric assay at 340 nm, which allowed quantitation of the reduction rate and the number of disulfide bonds reduced. Partial reduction of the alpha subunit with thioredoxin followed by S-carboxymethylation with iodol[2-3H]acetic acid and analysis of tryptic peptides indicated that all S-S bonds in the alpha subunit were surface oriented and equally reactive. The usefulness of thioredoxin reduction of disulfide bonds as a chemical probe of protein structure was shown by the much slower reaction of disulfide bonds in the intact hormone as compared to its two biologically inactive subunits.

Aerobiosis↗