Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Iodoacetamide”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed1982

Differential effects of dithiothreitol and iodoacetamide on corticotropin-releasing factor (CRF) activity of bovine hypothalamic CRFs and vasopressin.

Various fractions were tested in vivo for corticotropin-releasing factor (CRF) activity after Sephadex G-100 fractionation of 0.1-N HCl extracts of bovine hypophyseal stalk or cerebral cortex. Female rats pretreated with chlorpromazine, morphine, and Nembutal were used for CRF assay. CRF-A (void volume fractions; big CRF), CRF-B (Kav = 0.583), and CRF-C (salt volume fractions) of bovine hypophyseal stalk and lysine or arginine vasopressin all induced clear-cut stimulation of ACTH and corticosterone in the assay rat, whereas they were ineffective in acutely hypophysectomized rats. Control fractions purified from bovine cerebral cortex had no CRF activity. Treatment of arginine and lysine vasopressin and CRF-C with dithiothreitol and iodoacetamide completely abolished their CRF activity, whereas the CRF activities of CRF-A and CRF-B were unaltered by these treatments. Treatment with iodoacetamide alone had no effect on the CRF activity of any of these substances. Fractionation of either CRF-C or arginine vasopressin on Sephadex G-15 yielded a CRF-active peak at a Kav of 0.35. We conclude that 1) three different forms of CRF exist in bovine hypophyseal stalk; 2) CRF-A and CRF-B are unrelated to vasopressin and require neither a disulfide bond(s) nor a sulfhydryl group(s) for their CRF activity; 3) reduction of the disulfide bond of vasopressin destroys both CRF and antidiuretic activities; 4) CRF-C requires an intact disulfide bond(s) for its CRF activity and is likely to be either vasopressin itself or a substance closely related to vasopressin; and 5) CRF-B is likely to be the physiologically important form of bovine CRF.

Adrenocorticotropic Hormone↗
PubMed2001

Determination of lomefloxacin, an antibacterial drug, in pharmaceutical preparations based on its polarographic catalytic wave in the presence of 2-iodoacetamide.

In a 0.125 mol/L phosphate (pH 6.6)/2.5 x 10(-4) mol/L 2-iodoacetamide solution, lomefloxacin yields a response of a polarographic catalytic current. The second-order derivative peak current of the catalytic wave of lomefloxacin is proportional to its concentration in the range of 1.0 x 10(-8)-1.0 x 10(-6) mol/L (r = 0.998). The sensitivity of the catalytic wave is 25-times higher than that of the corresponding reduction wave for 5.0 x 10(-7) mol/L lomefloxacin. The proposed method was applied to the determination of lomefloxacin in pharmaceutical preparations. The polarographic reduction wave is ascribed to a one-electron reduction of the C=C bond of lomefloxacin zwitterion accompanied by an acid-base equilibrium. The catalytic wave should be caused by regeneration of the lomefloxacin molecule at electrode surface due to the one-electron reduction product being further oxidized by electroreductive intermediate products of 2-iodoacetamide.

Alkylating Agents↗
PubMed1976

Effect of fundic ulcers induced by iodoacetamide on development of gastric tumors in rats treated with N-methyl-N'-nitro-N-nitrosoguanidine.

The effect of ulcers induced by iodoacetamine on the development of gastric tumors by N-methyl-N'-nitro-N-nitrosoguanidine was studied in male Wistar rats. The ulcerative lesions induced by iodoacetamide were confined symmetrically to the fundic region along the limiting ridge in the stomach and the pyloric region was unaffected. Animals treated with iodoacetamide and N-methyl-N'-nitro-N-nitrosoguanidine produced a high incidence of tumors including adenocarcinoma in the fundic region. The incidence of tumors in the pyloric region in the control group was 80% but there were no tumors in the fundic region. The tumors in the fundic region were most frequently found in the same areas that ulcers had previously been induced. These findings suggest that ulceration and regeneration of the mucosa are important factors in gastric carcinogenesis induced in rats by N-methyl-N'-nitro-N-nitrosoguanidine.

Adenocarcinoma↗
PubMed1991

The influence of divalent cations and doxycycline on iodoacetamide-inhibitable leukocyte adherence.

Leukocyte adherence, an event critical to host defense, is reported to be dependent upon divalent cations. To test whether leukocyte binding is more influenced by the availability of Ca2+ or Mg2+, neutrophils and mononuclear leukocyte adherence to surfaces coated with differing proteins, in medium containing varying concentrations of Ca2+ and/or Mg2+ and induced with either FMLP or PMA were assessed. To account for nonspecific leukocyte-substrata interactions the OD's of iodoacetamide-inhibited adherent cell systems were subtracted from the OD values of adherent cells of noninhibited systems. Values presented were derived from OD's of iodoacetamide-inhibitable leukocyte binding. PMA was a much more potent inducer of leukocyte adherence than was FMLP, stimulating all available neutrophils and monocytes to adhere. In contrast, FMLP induced adherence by roughly 1/4 of the available neutrophils and few, if any, monocytes. Roughly the same binding pattern was noted whether surfaces were coated with albumin, fibrinogen, fibronectin, gelatin or serum. EDTA but not EGTA significantly suppressed leukocyte binding suggesting Mg2+ was more involved in binding than was Ca2+. Little leukocyte adherence to a substrata occurred in the absence of divalent cations, while enrichment of the medium with Mg2+ was more influential on cell binding than was enrichment with Ca2+. Interestingly, doxycycline, a member of the tetracycline family of drugs which has been reported to inhibit Mg(2+)-dependent neutrophil functions, had a slight inhibitory effect on neutrophil adherence at low drug concentrations, while it enhanced binding at higher doxycycline concentrations. In contrast, the tetracycline inhibited monocyte adherence in a dose-related manner.

Calcium↗
PubMed1977

Effect of iodoacetamide or Tween 60 on methylnitrosocyanamide carcinogenesis in rat glandular and forestomach.

The effect of iodoacetamide or Tween 60 on carcinogenicity of methylnitrosocyanamide (MNC) in rats was examined. A significant increase in the incidence of the forestomach tumors (P less than 0.01) was observed in rats treated with MNC and iodoacetamide simultaneously. Moreover, there were 2 cases of glandular stomach tumors in rats treated with MNC and Tween 60 simultaneously. They were one well-differentiated adenocarcinoma and one polypoid hyperplasia. This result indicates that MNC under certain conditions is carcinogenic to the glandular stomach of rats in addition to the forestomach. Tween 60 might act by facilitating direct contact between MNC and the glandular stomach mucosa.

Animals↗
PubMed1978

Induction of preneoplastic hyperplasia and carcinoma by N-methyl-N'-nitro-N-nitrosoguanidine from regenerated mucosa of ulcers induced by iodoacetamide in fundus of rat stomach.

Differences in susceptibility to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) of fundic mucosa in various states of regeneration after induction of ulcer with iodoacetamide were examined histologically in male Wistar rats. Iodoacetamide was given to rats in their drinking water, before (Group 1), with (Group 2), or after (Group 3) MNNG. Atypical hyperplasia in the renewed mucosa and pyloric gland metaplasia were observed on the ulcers in Group 1 in higher incidence than in Groups 2 and 3. In addition, adenocarcinoma developed in the ulcer of 2 of 17 effective animals in Group 1. These observations suggest that the mucosa showing pyloric gland metaplasia is more susceptible to MNNG than the young rapidly regenerating mucosa at the margin of ulcers.

Adenocarcinoma↗
PubMedDate not supplied

[Oxygen-binding properties of human hemoglobin solutions UV-irradiated in the presence of iodoacetamide].

Changes of oxygen-binding properties of human hemoglobin solutions modified by the different concentrations of iodoacetamide and by this chemical agent together with UV-light in doses 151 and 755 J/m2 has been studied by means of spectroscopy. It has been shown that addition of iodoacetamide to native hemoglobin solution (12:1) results in increase of the oxygen affinity and breach of the hem-hem interaction of hemoprotein. It has been ascertained that influence of UV-radiation on hemoglobin displays in photodissociation of the tetramers to protomers.

Adult↗
PubMed1993

An iodoacetamide spin-label selectively labels a cysteine side chain in an occluded site on the sarcoplasmic reticulum Ca(2+)-ATPase.

Sarcoplasmic reticulum vesicles were labeled with [14C]iodoacetamide spin-label (ISL) under conditions where time courses of the reaction predicted that one amino acid residue would be preferentially labeled. Solubilized tryptic peptides were separated by high-performance liquid chromatography following extensive digestion, and amino acid sequences were determined for major and minor radio-labeled peptides. Only one radio-labeled residue, Cys-674 on the Ca(2+)-ATPase, could be identified. Extensive incubation with excess label increased nonspecific labeling, but did not produce detectable amounts of any other reactive side chain residue. Time courses of the iodoacetamide spin-label reaction were compared to those of 6-(iodoacetamido)fluorescein (IAF), and the ISL reaction was found to be more selective, in accordance with previous studies showing that IAF labeled both Cys-674 and Cys-670 [Bishop, J. E., Squire, T. C., Bigelow, D. J., & Inesi, G. (1988) Biochemistry 27, 5233-5240]. Titrations with spin-broadening reagents NiCl2 and Ni-EDTA showed Cys-674 to be in a region with very low solvent accessibility. These titrations also showed the ATPase to be distributed between two alternating conformations based on the accessibility of the label to NiCl2.

Amino Acid Sequence↗
PubMed1973

Sensitizing ability and toxicity of iodoacetamide in radiotherapy of a C3H mouse mammary carcinoma.

The radiosensitizing effect of iodoacetamide was studied in a C3H mouse mammary carcinoma together with its toxicity to the host. TCD(50) or radiation dose to yield 50% tumour control frequency was determined in tumours treated or untreated with the agent. Results indicated that 15 mg/kg of iodoacetamide sensitized hypoxic tumour cells, as did atmospheric oxygen, and the sensitization was not detectable below this dose. Experiments with fractionated treatments suggested that the reoxygenation occurring during the treatment intervals of 24 hours might be more important in the sterilization of tumour cells than the agent.

Amides↗
PubMed1970

Properties and reaction with iodoacetamide of adenosine 5'-triphosphate-creatine phosphotransferase from human skeletal muscle. Further evidence about the role of the essential thiol group in relation to the mechanism of action.

1. The purification of creatine kinase from human and monkey skeletal muscle by horizontal electrophoresis on Sephadex blocks is described. 2. The purified enzymes are shown to have similar chemical and kinetic properties to the rabbit muscle enzyme and a common mechanism is inferred. 3. Iodoacetamide has a similar apparent second-order inhibition constant with the human and rabbit enzymes, but the inhibition does not go to completion with the former. This is even more marked with the monkey enzyme, which has more reactive thiol groups, but inhibition is only about 50%. 4. Single substrates have little effect on the inhibition by iodoacetamide, but with the primate enzymes, in contrast with the rabbit enzyme, high concentrations of ADP-Mg(2+) plus creatine convert the essential thiol group from being pH-independent into one with a normal ionization. Low concentrations of ADP-Mg(2+) plus creatine first enhance the rate of inactivation, but cause protection as the reaction proceeds. These results are interpreted to indicate an activation of the thiol group on the subunit to which the substrates bind and a co-operatively induced decrease in the activity of the thiol group on the other subunit which lacks substrates. 5. The effects of a substrate equilibrium mixture on the rate of inhibition are essentially those of ADP-Mg(2+) plus creatine. 6. Since no substrate combination affords significant protection to the thiol group associated with the catalytic site to which the substrates are bound, it is concluded that any mechanism involving the thiol group in a direct participation in the transition-state complex of the catalytic reaction must be abandoned unless the transition state is only a small part of the time taken for one catalytic cycle.

Adenosine Triphosphate↗
PubMed2000

Identification of an artifact in the mass spectrometry of proteins derivatized with iodoacetamide.

Derivatization of cysteinyl residues is often used to prevent the formation of disulfide bonds during protein isolation and analysis. The most commonly used reagents are iodoacetic acid and iodoacetamide, which increase the molecular mass of the protein by 58 or 57 Da, respectively, for each derivatized cysteine. A possible side reaction is derivatization of methionine. In our analysis of derivatized human lens alphaA-crystallins, we found an apparent molecular mass 48 Da lower than the mass expected for alphaA-crystallin with the cysteines carboxyamidomethylated. Analysis of a tryptic digest of this protein showed that both cysteines and one methionine had been derivatized. Peaks indicating a molecular mass 48 Da less than expected for the protein with only cysteines derivatized were attributed to fragmentation of the derivatized methionine through collision-induced dissociation in the electrospray ionization source. An awareness of this artifact is important to investigators searching for proteins and their modified forms in complex mixtures.

Aged↗
PubMed2005

Iodoacetamide-alkylated methionine can mimic neutral loss of phosphoric acid from phosphopeptides as exemplified by nano-electrospray ionization quadrupole time-of-flight parent ion scanning.

Formation of S-carbamidomethylmethionine (camMet) occurs as a side reaction during cysteine alkylation with iodoacetamide (IAA). In collision-induced dissociation, peptides with camMet show an abundant neutral loss of 2-(methylthio)acetamide (C3H7NOS = 105.025 Da) at moderate collision offset values which are similar to those optimal for loss of phosphoric acid (H3PO4 = 97.977 Da). Neutral loss analysis is used for spotting of phosphopeptides which contain phosphoserine (pSer) or phosphothreonine (pThr) residues. In the case where precursor ions cannot be accurately assigned in the survey spectrum (e.g. due to low ion abundance or signal overlap), the mass accuracy of a neutral loss tandem mass spectrometry (MS/MS) analysis depends on the precursor ion isolation window. For the charge states 2+, 3+ or 4+, a typical 3.5 Da precursor isolation window results in neutral loss windows of 7, 10.5 or 14 Da, respectively. Consequently, neutral loss of 105 Da from alkylated methionine residues can mimic the phosphoserine/phosphothreonine-specific neutral loss of 98 Da. In the evaluation of quadrupole time-of-flight (QTOF) parent ion scan data for neutral loss of H3PO4, this interference was frequently observed. It is illustrated in this study using the analysis of ovalbumin phosphorylation as an example. The +80 Da molecular weight shift connected with phosphorylation at serine or threonine may also be mimicked by carbamidomethylation of methionine through a combination with sodium adduction (+57 Da +22 Da = +79 Da). For highly sensitive neutral loss analysis of serine and threonine phosphorylation, careful data inspection is recommended if reduction and alkylation by IAA is employed.

Alkylation↗
PubMed1994

Modification of cysteine residues with N-methyl iodoacetamide.

Cysteine residues derivatized with N-methyl iodoacetamide (MIAA) can be analyzed by the Edman sequencing with a high degree of reliability. By HPLC, the phenylthiohydantoin (PTH) derivative of MIAA-modified cysteine eluted between dimethylphenylthiourea and PTH-Ala--a wide gap which is not occupied or interfered with by any other by-products or PTH amino acids. During extended Edman degradation, the recovery of PTH derivative of MIAA-modified Cys was as quantitative and reproducible as that of other stable PTH derivatives such as Ala, Val, and Leu.

Amino Acids↗
PubMed1982

Chicken liver fatty acid synthetase dimer: evidence of asymmetrical structure from iodoacetamide inhibition studies.

The condensing component of chicken liver fatty acid synthetase is inhibited by a sulfhydryl reagent, iodoacetamide, with a second-order rate constant of 0.23 M-1 sec-1 at pH 7.0 and 0 degrees. Complete inactivation requires the modification of approximately 8 -SH groups per dimer of the enzyme. Quantitation of the extent of inactivation in the presence of 1 mM acetyl CoA (which completely protects the enzyme against inactivation) and in its absence shows that complete inactivation results from the binding of approximately 1.1 mol of carboxamidomethyl residues per dimer. These data are consistent with the proposed functional asymmetry of the enzyme.

Acetyl Coenzyme A↗
PubMed1983

Thiol-dependent passive K/Cl transport in sheep red cells: III. Differential reactivity of membrane SH groups with N-ethylmaleimide and iodoacetamide.

Treatment with N-ethylmaleimide (NEM) is known to stimulate ouabain-insensitive, Cl- -dependent K+ transport in low K+ (LK) but not in high K+ (HK) sheep red cells (Lauf, P.K., and Theg, B.E., 1980, Biophys. Biochem. Res. Commun. 92:1422-1428). The dependence of this effect on the pH of pretreatment with NEM and/or iodoacetamide (IAA) was studied. Maximum stimulation of Cl- -dependent K+ transport in LK red cells was produced by prior treatment with 1-5 mM NEM at pH 6 at which only about 30-40% of the 10(7) SH groups present per membrane reacted. At pH 6 no NEM effect was seen on Nap K+ fluxes in HK red cells. Treatment with NEM below pH 6 enhanced Cl- -independent K+ transport in both LK and HK red cells. At higher pH values or higher concentrations the NEM-stimulation of K+ transport was reduced and absent at pH 8.7. Exposure of LK cells to 5 mM IAA prior to NEM abolished the stimulatory effect of NEM on K+ transport. Hence at least two different chemical groups were reacting with NEM, and more alkaline SH or NH2 groups whose reaction with NEM leads to an inhibition of the NEM effect brought about at pH 6.

Animals↗
PubMed1987

Thiol-dependent passive K/Cl transport in sheep red cells: VII. Volume-independent freezing by iodoacetamide, and sulfhydryl group heterogeneity.

The sulfhydryl (SH) reagent iodoacetamide (IAAM) inhibits stimulation of Cl-dependent K transport in low K (LK) sheep red cells by another SH reagent, N-ethylmaleimide (NEM), without itself activating this transport pathway (J. Membrane Biol., 1983, 73:257-261). We now report that IAAM alone, acting with a kinetic slower than NEM, sharply reduced the capability of the Cl-dependent K transport system to regulate its activity in response to cell volume changes. This effect of IAAM did not depend on the cell volume maintained during chemical treatment, a fact ruling out that the reactivity of the SH groups with IAAM was a function of the volume-dependent turnover rate of the transporter. On the other hand, the prevention of the NEM-stimulatory effect on Cl-dependent K transport was found to be volume-dependent since 1) the rate with which IAAM blocked the subsequent NEM action was twice as fast in cells swollen in 250 mOSM as opposed to cells shrunken in 370 mOSM media, and 2) the dose response of the IAAM effect was different in swollen and shrunken cells. The action of IAAM with or without subsequent treatment with NEM seemed to be independent of cellular ATP which is required for full expression of the stimulatory modification of Cl-dependent K transport by NEM (Am. J. Physiol., 1983, 245:C445-C448). Clusters of SH groups on the Cl-dependent K transporter apparently react differently with IAAM and NEM when separately applied but, used in combination, reflect a complex volume-dependent effect that may reveal a "volume-sensing" component of the transport molecule.

Animals↗
PubMed1994

Use of N,N'-polymethylenebis(iodoacetamide) derivatives as probes for the detection of conformational differences in tubulin isotypes.

Mammalian brain tubulin is an alpha beta heterodimer; both alpha and beta exist in 6-7 isotypic forms which differ in their amino acid sequences. By the use of isotype-specific monoclonal antibodies, we have previously shown that we can purify the alpha beta II, alpha beta III, and alpha beta IV tubulin dimers from bovine brain. We have also observed that these isotypes differ in their distribution in vivo and their polymerization and drug-binding properties in vitro. We have now explored the question of whether the isotypically purified dimers differ in their overall conformation using as probes compounds of the N,N'-polymethylenebis (iodoacetamide) series which are known to form discrete intrachain cross-links in beta-tubulin. These compounds have the structure ICH2CONH(CH2)nNHCOCH2I. One of these cross-links, designated beta s, is between cys12 and either cys201 or cys211. The other, designated beta*, is between cys239 and cys354. The beta* cross-link forms in alpha beta II and alpha beta IV but not in alpha beta III; this is not surprising in view of the fact that alpha beta III has serine at position 239 instead of cysteine. However, alpha beta III is also unable to form the beta s cross-link, although it appears to have all three cysteines which may be involved in the cross-link. This suggests that at least one of the sulfhydryls involved in the cross-link may be inaccessible in alpha beta III. Although both alpha beta II and alpha beta IV can form the beta s cross-link, the dependence on cross-linker chain length is different. alpha beta II forms beta s with derivatives in which n = 2, 4, 5, 6, and 7 but not with those in which n = 3 or 10. In contrast, alpha beta IV forms beta s with derivatives in which n = 2, 3, 4, 5, 6, 7, and 10. These results imply that the beta s sulfhydryls are slightly more accessible in alpha beta IV and are therefore less dependent on the conformation of the cross-linker to react with it. It appears, therefore, that the alpha beta II, alpha beta III, and alpha beta IV dimers each have unique conformations. This may help to explain the different assembly and drug-binding properties of these dimers.

Animals↗
PubMed2005

Synthesis and biological activity of new iodoacetamide derivatives on mutants of squalene-hopene cyclase.

New iodoacetamide derivatives, containing a dodecyl or a squalenyl moiety, were synthesized. The effect of these new thiol-reacting molecules was studied on two mutants of Alicyclobacillus acidocaldarius squalene-hopene cyclase constructed especially for this purpose. In the quintuple mutant, all five cysteine residues of the enzyme are substituted with serine; in the sextuple mutant, this quintuple substitution is accompanied by the substitution of aspartate D376, located at the enzyme's active site, with a cysteine. N-Dodecyliodoacetamide had little activity toward either mutant, whereas N-squalenyliodoacetamide showed a stronger effect on the sextuple than on the quintuple mutant, as expected.

Bacillus↗