An evaluation of the cross-linking model for the interaction of insulin with its receptor

1997 ◽  
Vol 272 (6) ◽  
pp. E1136-E1144 ◽  
Author(s):  
B. J. Hammond ◽  
J. Tikerpae ◽  
G. D. Smith
Keyword(s):  
Insulin Receptor ◽  
Insulin Binding ◽  
Cross Linking ◽  
Cross Link ◽  
Binding Studies ◽  
Systematic Analysis ◽  
Concentration Difference ◽  
Receptor Complexes ◽  
Insulin Molecule ◽  
The Cross

The cross-linking model for insulin receptor interactions, in which a single insulin molecule may form a cross-link between an insulin receptor's alpha-subunits, has been expressed as a formal compartmental model and subjected to a systematic analysis, examining a number of predictions that have been made for this model. The kinetic parameters for the model were obtained by matching data from insulin receptor equilibrium binding studies and rates of formation of the insulin receptor complex. This analytical study has allowed a clear description of the kinetics of the ligand receptor complexes involved in such a mechanism. We conclude that the cross-linking model accounts for the anomaly of the 10-fold concentration difference in high- and low-affinity binding sites found when insulin binding is analyzed by conventional means. However, the phenomenon of acceleration of dissociation of labeled ligand by unlabeled ligand cannot be accounted for as an intrinsic part of the model. We suggest that this phenomenon arises from the destabilization of cross-link formation when a second insulin molecule binds.

EXPERIMENTAL VALIDATION OF THE CHARLESBY AND HORIKX MODELS APPLIED TO DE-VULCANIZATION OF SULFUR AND PEROXIDE VULCANIZATES OF NR AND EPDM

2016 ◽  
Vol 89 (4) ◽  
pp. 671-688 ◽  
Author(s):  
M. A. L. Verbruggen ◽  
L. van der Does ◽  
W. K. Dierkes ◽  
J. W. M. Noordermeer
Keyword(s):  
Experimental Validation ◽  
Main Chain ◽  
Sol Gel ◽  
Chain Scission ◽  
Cross Linking ◽  
Cross Link ◽  
Practical Reality ◽  
Cross Links ◽  
The Cross ◽  
Theoretical Considerations

ABSTRACT The theoretical model developed by Charlesby to quantify the balance between cross-links creation of polymers and chain scission during radiation cross-linking and further modifications by Horikx to describe network breakdown from aging were merged to characterize the balance of both types of scission on the development of the sol content during de-vulcanization of rubber networks. There are, however, disturbing factors in these theoretical considerations vis-à-vis practical reality. Sulfur- and peroxide-cured NR and EPDM vulcanizates were de-vulcanized under conditions of selective cross-link and random main-chain scissions. Cross-link scission was obtained using thiol-amine reagents for selective cleavage of sulfur cross-links. Random main-chain scission was achieved by heating peroxide vulcanizates of NR with diphenyldisulfide, a method commonly employed for NR reclaiming. An important factor in the analyses of these experiments is the cross-linking index. Its value must be calculated using the sol fraction of the cross-linked network before de-vulcanization to obtain reliable results. The values for the cross-linking index calculated with sol-gel data before de-vulcanization appear to fit the experimentally determined modes of network scission during de-vulcanization very well. This study confirms that the treatment of de-vulcanization data with the merged Charlesby and Horikx models can be used satisfactorily to characterize the de-vulcanization of NR and EPDM vulcanizates.

scholarly journals Improving the Color Stability of Naturally Colored Silk by Cross-Linking the Sericin with Phytic Acid

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Mingbo Ma ◽  
Pirah Ayaz ◽  
Wanhui Jin ◽  
Wenlong Zhou
Keyword(s):  
Phytic Acid ◽  
Color Stability ◽  
Constant Level ◽  
Cross Linking ◽  
Color Fastness ◽  
Cross Link ◽  
Biomedical Field ◽  
The Cross

The color of naturally colored silk (NCS) fades easily during home washing due to the loss of pigment accompanied by dissolution of the sericin. In this study, phytic acid was used to cross-link the sericin of NCS and reduce its solubility, aiming at improving the color fastness of NCS to repeated washing. It was found that the sericin-fixing effect increased as the concentration of phytic acid to 1.0 wt% and the cross-linking time to 5 h increased and then reached a constant level. Cross-linking at pH 7.0-8.5 and temperature 30-40°C could obtain relatively good sericin-fixing effects. The cross-linked NCS showed low sericin loss during the degumming and had much better color fastness to repeated washing as compared with the samples before cross-linking. The cross-linking method proposed in this study may be not only a kind of solution for improving the color fastness of NCS with high practicality but also an alternative for cross-linking sericin-based materials in the biomedical field.

Effect of cross-linking agents on insulin associated responses in adipocytes

1982 ◽  
Vol 60 (10) ◽  
pp. 987-1000 ◽  
Author(s):  
H. Joseph Goren ◽  
C. Ronald Kahn
Keyword(s):  
Insulin Receptor ◽  
Glucose Transport ◽  
Free Amino ◽  
Glucose Oxidation ◽  
Insulin Binding ◽  
Cross Linking ◽  
Amino Group ◽  
Amino Groups ◽  
Disuccinimidyl Suberate ◽  
Reactive Groups

The effect of 10 bifunctional cross-linking agents and four monofunctional analogues was studied on isolated adipocytes. [125I]Insulin binding and degradation, basal and insulin-stimulated glucose oxidation, and 3-O-methyl glucose uptake were measured. Two cross-linkers, which possess succinimide ester residues (disuccinimidyl suberate and dithiobis(succinimidyl propionate)) and react selectively with amino groups, appeared to react relatively specifically with the insulin receptor. Both produced a slight stimulation of basal glucose transport and metabolism, a marked inhibition of insulin-stimulated glucose transport and metabolism, and a marked decrease in insulin binding. Pretreatment of cells with unlabelled insulin partially blocked the effect of disuccinimidyl suberate, and as has been previously shown, disuccinimidyl suberate cross-linked insulin to its receptor. A monofunctional analogue of these compounds was 100-fold less active in altering cellular metabolic activity. Bisimidates, such as dimethyl suberimidate, dimethyl adipimidate, and dimethyl dithiobispropionimidate, also react with free amino groups but are more hydrophilic. These agents produced similar effects on glucose oxidation as the succinimide esters, but had little or no effect on insulin binding. The effects of these agents are not blocked by insulin and they do not cross-link insulin to its receptor. Mixed bifunctional reagents containing either a succinimide ester or an imidate and a group which reacts with thiols produced effects similar to the cross-linkers containing two succinimide groups or bisimidates, respectively. The bifunctional arylating agents difluorodinitrobenzene and bis(fluoronitrophenyl)sulfone produce marked effects on insulin binding and glucose oxidation at micromolar concentrations, but the monofunctional analogue fluorodinitrobenzene is almost equally active suggesting that with these compounds chemical modifications and not cross-linking was important. With neither the mixed bifunctional reagents, nor the arylating agents, did insulin pretreatment alter the effect of cross-linker and none of these agents cross-linked [125I]insulin to its receptor. These data suggest that the insulin receptor possesses a free amino group in a hydrophobic environment in its active site. A reactive amino group in a hydrophilic environment as well as other reactive groups are also present in some component of the insulin receptor–effector complex. Chemical modification or cross-linking of these functional groups results in an inhibition or mimicking of insulin action. Further study will be required to identify the exact locus of these sites.

scholarly journals A SEX-LINKED DEFECT IN THE CROSS-LINKING OF COLLAGEN AND ELASTIN ASSOCIATED WITH THE MOTTLED LOCUS IN MICE

1974 ◽  
Vol 139 (1) ◽  
pp. 180-192 ◽  
Author(s):  
David W. Rowe ◽  
Ermona B. McGoodwin ◽  
George R. Martin ◽  
Michael D. Sussman ◽  
Douglas Grahn ◽  
...  
Keyword(s):  
Coat Color ◽  
Cross Linking ◽  
Genetic Abnormality ◽  
Cross Link ◽  
Skin Collagen ◽  
The Cross ◽  
Tissue Abnormalities ◽  
Link Formation ◽  
Experimental Lathyrism

A genetic abnormality in collagen and elastin cross-linking resembling experimental lathyrism has been identified in mice. The defect is an X-linked trait, attributed to the mottled locus which also influences coat color. The affected mice have aneurysms of the aorta and its branches, weak skin, and bone deformities in a spectrum of severity varying with the alleles at the mottled locus. A defect in the cross-linking of collagen was demonstrated in the skin of the affected animals by a marked increase in collagen extractability and a reduced proportion of cross-linked components in the extracted collagen. A decrease in lysine-derived aldehyde levels was found in both skin collagen and aortic elastin similar to that found in lathyritic tissue. Furthermore the in vitro formation of lysine-derived aldehyde was reduced. Thus the cause of the connective tissue abnormalities in these mice appears to be a defect in cross-link formation due to an impairment in aldehyde formation.

scholarly journals Chemistry of collagen cross-linking: biochemical changes in collagen during the partial mineralization of turkey leg tendon

1997 ◽  
Vol 322 (2) ◽  
pp. 535-542 ◽  
Author(s):  
Lynda KNOTT ◽  
John F. TARLTON ◽  
Allen J. BAILEY
Keyword(s):  
Collagen Matrix ◽  
Cross Linking ◽  
Cross Link ◽  
Lysine Residues ◽  
Collagen Mineralization ◽  
Cross Links ◽  
The Cross ◽  
Calcified Tissues ◽  
Turkey Leg Tendon ◽  
Collagen Cross Linking

With age, the proximal sections of turkey leg tendons become calcified, and this phenomenon has led to their use as a model for collagen mineralization. Mineralizing turkey leg tendon was used in this study to characterize further the composition and cross-linking of collagen in calcified tissues. The cross-link profiles of mineralizing collagen are significantly different from those of other collagenous matrices with characteristically low amounts of hydroxylysyl-pyridinoline and the presence of lysyl-pyridinoline and pyrrolic cross-links. However, the presence of the immature cross-link precursors previously reported in calcifying tissues was not supported in the present study, and was found to be due to the decalcification procedure using EDTA. Analysis of tendons from young birds demonstrated differences in the cross-link profile which indicated a higher level of hydroxylation of specific triple-helical lysines involved in cross-linking of the proximal tendon. This may be related to later calcification, suggesting that this part of the tendon is predestined to be calcified. The minimal changes in lysyl hydroxylation in both regions of the tendon with age were in contrast with the large changes in the cross-link profile, indicating differential hydroxylation of the helical and telopeptide lysine residues. Changes with age in the collagen matrix, its turnover and thermal properties in both the proximal and distal sections of the tendon clearly demonstrate that a new and modified matrix is formed throughout the tendon, and that a different type of matrix is formed at each site.

scholarly journals Influence of the chemical structure of cross-linking agents on properties of thermally reversible networks

2016 ◽  
Vol 88 (12) ◽  
pp. 1103-1116 ◽  
Author(s):  
Lorenzo Massimo Polgar ◽  
Robin R.J. Cerpentier ◽  
Gijs H. Vermeij ◽  
Francesco Picchioni ◽  
Martin van Duin
Keyword(s):  
Chemical Structure ◽  
Chemical Conversion ◽  
Rubber Matrix ◽  
Cross Linking ◽  
Cross Link ◽  
Molar Amount ◽  
Link Density ◽  
Cross Link Density ◽  
Cross Linker ◽  
The Cross

Abstract It is well-known that the properties of cross-linked rubbers are strongly affected by the cross-link density. In this work it is shown that for thermoreversibly cross-linked elastomers, the type and length of the cross-linker also have a significant effect. A homologous series of diamine and bismaleimide cross-linkers was used to cross-link maleic-anhydride-grafted EPM irreversibly and furan-modified EPM thermoreversibly, respectively. Bismaleimide cross-linkers with a polarity close to that of EPM and a relatively low melting point have a better solubility in the rubber matrix, which results in higher chemical conversion and, thus, higher cross-link densities at the same molar amount of cross-linker. Samples cross-linked with different spacers (aromatic and aliphatic spacers of different lengths) were compared at the same cross-link density to interpret the effects on the material properties. The rigid character of the short aliphatic and the aromatic cross-linkers accounts for the observed increase in hardness, Young´s modulus and tensile strength with respect to the longer, more flexible aliphatic cross-linkers. In conclusion, the structure of the cross-linking agent can be considered as an alternative variable in tuning the rubber properties, especially for thermoreversibly cross-linked rubber.

FANCD2 Localizes to Cross-Linked Induced Nuclear Foci That Are Distinct From Those to Which αaII Spectrin and the Cross-Link Repair Protein, XPF, Co-Localize, Indicating An Involvement of These Proteins in Different Steps of the DNA Interstrand Cross-Link Repair Process.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 3196-3196
Author(s):  
Pan Zhang ◽  
Deepa Sridharan ◽  
Michael Acosta ◽  
Muriel Lambert
Keyword(s):  
Time Course ◽  
Repair Process ◽  
Myelogenous Leukemia ◽  
Cross Linking ◽  
Cross Link ◽  
Repair Protein ◽  
Interstrand Cross Links ◽  
Cross Links ◽  
Nuclear Foci ◽  
The Cross

Abstract Abstract 3196 Poster Board III-133 The hereditary bone marrow failure disorder, Fanconi anemia (FA), is characterized by a markedly increased incidence of acute myelogenous leukemia, diverse congenital abnormalities and a defect in ability to repair DNA interstrand cross-links. We have previously shown that in FA cells there is a deficiency in the structural protein nonerythroid a spectrin (aSpII), which is involved in repair of DNA interstrand cross-links and binds to cross-linked DNA. aSpII co-localizes in nuclear foci with FANCA and the cross-link repair protein, XPF, after normal human cells are damaged with a DNA interstrand cross-linking agent. One of the FA proteins which is thought to play an important role in the repair of DNA interstrand cross-links is FANCD2, which is known to form nuclear foci after cross-link damage. The present study was undertaken in order to get a better understanding of the relationship between aSpII and FANCD2, whether they interact with each other during the DNA repair process and co-localize in damage-induced nuclear foci. Immunofluorescence microscopy was carried out to determine whether these proteins co-localized in nuclear foci after cells were damaged with a DNA interstrand cross-linking agent, 8-methylpsoralen plus UVA light (8-MOP) or mitomycin C (MMC). Time course measurements showed that FANCD2 foci were first visible at 2 hours after damage and increased up to 16 hours and were still present at 72 hours after damage. This time course of foci formation correlated with levels of monoubiquitination of FANCD2. Measurement of gH2AX foci formation showed that the time course of foci formation was similar to that of FANCD2 measured up to 72 hours post damage. In contrast, aSpII foci were first visible between 8-10 hours after damage. The number of these foci peaked at 16 hours and by 24 hours foci were no longer observed. Co-localization studies showed that there was little co-localization of the FANCD2 and aSpII foci over this time course. This indicates that these two proteins may be involved in different steps in the DNA interstrand cross-link repair process. Based on models that have been proposed for the role of FANCD2 in the repair of DNA interstrand cross-links, we propose that, after DNA damage, FANCD2 localizes at DNA replication forks stalled at sites of interstrand cross-links and aids in the assembly of proteins at this site. This is followed by localization of aSpII and XPF and other proteins involved in the initial incision steps in DNA interstrand cross-link repair where they play a role in the unhooking of the cross-link. FANCD2 is then involved in subsequent steps in the repair process, which involve homologous recombination. Thus two proteins, FANCD2 and aSpII, both of which have been shown to be critical for the DNA interstrand cross-link repair process may be involved in different or distinct steps in this repair process. Deficiencies in these proteins would impact on DNA interstrand cross-link repair and, as we have shown for aIISp, would have an adverse effect on the genomic stability of FA cells. . Disclosures No relevant conflicts of interest to declare.

scholarly journals A structural model for desmosine cross-linked peptides

1978 ◽  
Vol 173 (2) ◽  
pp. 617-625 ◽  
Author(s):  
R P Mecham ◽  
J A Foster
Keyword(s):  
Amino Acid ◽  
Structural Model ◽  
Partial Sequence ◽  
Cross Linking ◽  
Amino Acid Residues ◽  
Cross Link ◽  
Link Model ◽  
The Cross ◽  
Precursor Molecules

Desmosine-enriched peptides were isolated from a thermolysin digest of bovine ligamentum nuchae elastin and a partial sequence was determined. A ‘two-cross-link’ model is proposed in which a second cross-link, perhaps lysinonorleucine, joins two peptide chains approx. 35 amino acid residues removed from the desmosine. Implied in this model is a certain asymmetry or directionality which places restrictions on the ‘sense’ of the peptide chains (either always parallel or anti-parallel) in order to align the cross-linking sites. Imposing such restrictions raises the possibility of specific alignment of elastin precursor molecules by microfibrillar proteins and/or aligning peptides on the precursor molecules themselves.

scholarly journals An Atomic Model of Actin Filaments Cross-Linked by Fimbrin and Its Implications for Bundle Assembly and Function

2001 ◽  
Vol 153 (5) ◽  
pp. 947-956 ◽  
Author(s):  
Niels Volkmann ◽  
David DeRosier ◽  
Paul Matsudaira ◽  
Dorit Hanein
Keyword(s):  
Conformational Changes ◽  
Structural Characterization ◽  
Actin Polymerization ◽  
Two Dimensions ◽  
Atomic Model ◽  
Cross Linking ◽  
Cross Link ◽  
Actin Bundles ◽  
The Cross ◽  
And Function

Actin bundles have profound effects on cellular shape, division, adhesion, motility, and signaling. Fimbrin belongs to a large family of actin-bundling proteins and is involved in the formation of tightly ordered cross-linked bundles in the brush border microvilli and in the stereocilia of inner ear hair cells. Polymorphism in these three-dimensional (3D) bundles has prevented the detailed structural characterization required for in-depth understanding of their morphogenesis and function. Here, we describe the structural characterization of two-dimensional arrays of actin cross-linked with human T-fimbrin. Structural information obtained by electron microscopy, x-ray crystallography, and homology modeling allowed us to build the first molecular model for the complete actin–fimbrin cross-link. The restriction of the arrays to two dimensions allowed us to deduce the spatial relationship between the components, the mode of fimbrin cross-linking, and the flexibility within the cross-link. The atomic model of the fimbrin cross-link, the cross-linking rules deduced from the arrays, and the hexagonal packing of actin bundles in situ were all combined to generate an atomic model for 3D actin–fimbrin bundles. Furthermore, the assembly of the actin–fimbrin arrays suggests coupling between actin polymerization, fimbrin binding, and crossbridge formation, presumably achieved by a feedback between conformational changes and changes in affinity.

scholarly journals Disulphide cross-linking of smooth-muscle and non-muscle caldesmon to the C-terminus of actin in reconstituted and native thin filaments

1993 ◽  
Vol 294 (1) ◽  
pp. 63-67 ◽  
Author(s):  
P Graceffa ◽  
L P Adam ◽  
W Lehman
Keyword(s):  
Smooth Muscle ◽  
Cysteine Residue ◽  
Cross Linking ◽  
Cross Link ◽  
Thin Filaments ◽  
Chicken Gizzard ◽  
Terminal Domain ◽  
Binding Interface ◽  
C Terminus ◽  
The Cross

It was reported that chicken gizzard smooth-muscle caldesmon Cys-580 can be disulphide-cross-linked to the C-terminal pen-ultimate residue (Cys-374) of actin, indicating that these residues are close in the protein complex [Graceffa, P. and Jancso, A. (1991) J. Biol. Chem. 266, 20305-20310]. Since the possibility that the cross-link involves a cysteine residue other than actin Cys-374 was not absolutely excluded, more direct evidence was sought for the identify of the cysteine residues involved in the cross-link. We show here that caldesmon could not be disulphide-cross-linked to actin which had Cys-374 removed by carboxypeptidase A digestion, providing direct support for the participation of actin Cys-374 in the cross-link to caldesmon. In order to assign the caldesmon cysteine residue involved in the cross-link, use was made of caldesmon from porcine stomach muscle, which is shown to contain one cysteine residue close to, or at, position 580, in contrast with chicken gizzard caldesmon, which has an additional cysteine residue at position 153. The porcine stomach caldesmon also formed a disulphide-cross-link to actin, further supporting the original conclusion that Cys-580 of the chicken gizzard caldesmon had been cross-linked to actin. Disulphide-cross-linking with similar yield was also observed in native chicken gizzard muscle thin filaments, indicating that the interaction between actin and the C-terminal domain of caldesmon is the same in native and reconstituted thin filaments. The much smaller non-muscle isoform of caldesmon, from rabbit liver, could be similarly cross-linked to actin, consistent with the sequence similarity between the C-terminal domain of muscle and non-muscle caldesmon. The ability to cross-link caldesmon Cys-580 to actin Cys-374 suggests the possibility that the Cys-580 region of caldesmon and the C-terminus of actin form part of the actin-caldesmon binding interface.

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