Coordination Linkage Research Articles

Perceptual-motor coordination and adaptation during locomotion: determinants of prism adaptation in hall exposure.

Adaptation to prismatic displacement was examined under a number of conditions with locomotion in a hallway exposure. In general, total prism adaptation was inversely related to secondary cognitive load (presence or absence of mental arithmetic) and the relative magnitude of visual and proprioceptive shift depended upon the availability of visible sound sources in the hall environment. When the speaking experimenter was visible to the subject, visual shift was greater than proprioceptive shift, but when the experimenter was not visible and]or was silent, proprioceptive shift was greater than visual shift. No relationship has been detected between locomotion (walking rate) and either prism adaptation or cognitive load. These results are consistent with a model which assumes that the total adaptive response depends upon the available capacity to establish and maintain coordinative linkage between discordant systems, whereas locus of adaptive recalibration depends upon the direction of these coordinative linkages, discordance and adaptation occurring in the guided system(s). The available capacity for coordinative linkage depends upon cognitive load, whereas the directionality of linkage is independently determined by task structure. Locomotion is assumed to be mediated by a sensorimotor system that does not involve the distorted positional information.

The effect of alkali salt on solvent–polyacrylonitrile interaction

AbstractIn solvent spinning of polyacrylonitrile from DMF or DMSO, it is observed that complete removal of solvent is rather difficult. It is shown that addition of Lithium salt, e.g., lithium bromide to the solution before casting a film helps in removing the solvent easily. The probable mechanism of the action of lithium salt in solvent removal is investigated, and it has been shown that the formation of coordinate linkage with the ion stops solvent bonding.

Control and Coordination Links in the Metropolitan System of Cities: The South as Case Study

Control and coordination linkages are integral features of the system of cities, but few studies have directly measured them. This study examines the structure and degree of these linkages in the context of ecological theory. The results provide support for the hypotheses derived from the theory. Linkages are hierarchically organized, and the regional metropolis and higher-level metropolises at the national scale occupy pivotal positions as intermediaries for lower-level metropolises. Although national links are important, interurban links that include the regional metropolis and its hinterland cities remain a major factor in the system of cities even in a society that is often characterized as shifting from a local/regional to a national orientation.

Control and Coordination Links in the Metropolitan System of Cities: The South as Case Study

Control and coordination linkages are integral features of the system of cities, but few studies have directly measured them. This study examines the structure and degree of these linkages in the context of ecological theory. The results provide support for the hypotheses derived from the theory. Linkages are hierarchically organized, and the regional metropolis and higher-level metropolises at the national scale occupy pivotal positions as intermediaries for lower-level metropolises. Although national links are important, interurban links that include the regional metropolis and its hinterland cities remain a major factor in the system of cities even in a society that is often characterized as shifting from a locallregional to a national orientation. Metropolitan interdependence is an integral feature of the control and coordination function of metropolises, but few studies have explicitly examined intermetropolitan linkages in the context of the ecological theory of the system of cities.1 Most linkages fall into two broad categories. The first includes control and coordination links; these typically involve the exercise of authority and power relations. The bases of differential authority and power derive from variable access to economic resources such as capital, specialized business information, and exceptional business skills. Examples of these control and coordination links are the management ties between corporate headquarters and lower levels of the corporation, the flow of orders between retailers and wholesalers, and the financial ties between banks. The second broad category includes the physical linkages which are controlled and coordinated by metropolises; these are chiefly transportation-based, such as commodity flows and business travel.

Rare‐earth‐metal‐containing polymers. 5. Synthesis, characterization, and fluorescence properties of Eu3+‐polymer complexes containing carboxylbenzoyl and carboxylnaphthoyl ligands

AbstractPartially 2‐carboxylbenzoyl (1) and 3‐carboxyl‐2‐naphthoyl (2) substituted polystyrene were prepared by the Friedel‐Crafts reaction of polystyrene with corresponding dicarboxylic anhydrides. Europium (III) salts of (1) and (2) and the copolymer of 4‐vinylbenzoyl 2′‐carboxylbenzoate‐di(2‐benzoyl benzoate) and styrene (5) were prepared. Polymer (5) was prepared by the copolymerization of the Eu3+ salt of 4‐vinylbenzoyl 2′‐benzoate and 2‐benzoylbenzoate (ratio 1:2) with styrene. The fluorescence emission intensity was measured on fine powder samples. The intensity of (5) increased linearly as the Eu content increased. However, for the 1 and 2 systems the intensity reached a maximum at a Eu content as small as 0.5 wt% and remained constant when further increases were made. This phenomenon was accounted for by steric hindrance and a decrease in the freedom of bond rotation, which prevent the formation of multiple coordination linkages between Eu3+ and the benzoate groups.

Electron diffraction investigation of the molecular structures of the addition compounds Br 3Al.NH 3 and Br 3Ga.NH 3 in the vapour phase

According to an electron diffraction analysis, the molecular geometries of the addition compounds Br 3Al.NH 3 and Br 3Ga.NH 3 closely resemble those of their chlorine analogues. The coordination linkages and the acceptor parts are characterized by the following internuclear distances ( r a): Al-N 1.997 ± 0.019 Å. Ga-N 2.081 ± 0.023 Å, Al-Br 2.264 ± 0.005 Å, Ga-Br 2.288 ± 0.005 Å, Br· Br(Al) 3.834 ± 0.008 Å, and Br· Br(Ga) 3.884 ± 0.008 Å. Applying the estimated harmonic corrections, the bond angles (∠ α) are 116.1° and 116.6° for the aluminium and gallium complexes respectively.

Effects of metal ions and flavonoids on the oxidation of ascorbic acid.

Effects of metal ions and flavonoids on the oxidatio of ascorbic acid (I) have been investigated polarographically in the acetate buffer solution of pH 5.4. since I gives a diffusion-controlled anodic wave due to a two-electron oxidation to form dehydroascorbic acid, the rate of the oxidation of I can be followed by measuring the change in the limiting current of I with time. The rate of the oxidation of I was enhanced by the presence of some metal ions. Among them, the effect of copper (II) was especially pronounced. Such the fact can be explained on the basis of the formation of a coordinative linkage between metal and ascorbate ions and the reducibility of metal ions. Contrary to this, flavonoids exhibited an inhibition effect on the copper (II)-catalyzed oxidation of I. The effect became more marked in the order of 3-hydroxyflavone<rutin<quercetin, but no inhibition was observed for flavone. From the experimental result that the complex forming tendency of copper (II) with flavonoids increase in the order of flavone<3-hydroxyflavone<rutin<quercetin, a decrease in the concentration of free copper (II) as a result of the complex formation between flavonoids and copper (II), was found to be primarily responsible for the inhibition effect of flavonoids.

Emission mössbauer studies of some cobalamins with with and without coordination linkage to the 5,6-dimethyl-benzimidazole base

The emission Mössbauer spectra of “base on” and “base off” forms of the cyanocob(III)alamin (vitamin B 12) and the cob(II)alamin (B 12r) and the cob(I)alamin (B 12s) are studied. The s-electron density on the daughter iron nucleus as reflected by the isomer shift does not change very much while going from B 12 → B 12r → B 12s especially for the latter, despite the fact that the increasing population of the d subshell is expected to enhance the shielding of the s-electron cloud resulting in diminution of s-electron density on the iron nucleus. These observations can be rationalized if one invokes considerable delocalization of d π electrons from the daughter iron atom onto the corrin ring and also the appreciable hybrid character of d z 2 which permits increase of the 4 s-electron density concomitantly with an increase in the population of d z 2 orbital. The quadrupole splitting is perhaps predominantly determined by the anisotropy of covalent bonding to the iron atom by the corrin ring and the axial ligands. In the “base off” forms, a water molecule replaces the coordinated benzimidazole base, whereby the α-bonding of the axial ligand (s) is further diminished. The enhanced anisotropy of covalent bonding results in an increase in the magnitude of the quadrupole splittings for the “base off” forms. The finger prints of the “base on” and the “base off” B 12 and B 12r and B 12s would be valuable in identifying the intermediates in enzymatic reactions involving B 12.

Catalytic effects in reactions of chromium(III) part II: The role of excess ligand buffer in complexation of Cr(III) with some aminopolycarboxylic acids

The complexation of Cr (III) by EDTA, HEDTA and DCTA is channelled through ion pair formation between Cr (III) and the ambient ligand species. The ion pair further undergoes deprotonation giving rise to hydroxo chromium2+ species in the immediate vicinity of the counter ligand anion which helps in achieving the first coordination linkage between Cr(III) and the ligand.

Normal coordinate analysis of trimethylantimony oxide

The infrared and Raman spectra of trimethylantimony oxide and its deuterated analogue were recorded. Assignments were made and a normal coordinate analysis was carried out. A polar coordinate linkage is proposed for the SbO bond.

Reduction of fluorescence from high-area oxides of the silica, γ-alumina, silica-alumina, and Y-zeolite types and Raman spectra for a series of molecules adsorbed on these surfaces

It is shown that strong fluorescence that occurs with untreated high-area samples of porous silica-glass, silica gel, Cab-O-Sil, γ-aluminas, a silica-alumina and sodium Y zeolite is in all cases eliminated or greatly reduced by heating in oxygen for several hours at 500 °C. This fluorescence is attributed to traces of hydrocarbons decomposed on the acidic oxide surfaces that burn away in oxygen. Some degree of fluorescence returns when alumina-containing oxides are heated at elevated temperatures in a normal high vacuum; this is attributed to slow migration of hydrocarbon impurities. Certain organic molecules, such as furan and acetone, also give rise to new fluorescence, through decomposition, on contact with porous glass surfaces or while a Raman spectrum is being obtained. After heating in oxygen at 500 °C the aluminas or alumina-containing oxides exhibit a residual weaker fluorescence between 13,000 and 14,600 cm −, which may be attributed to traces of Fe 3+ impurities. Raman scattering has been observed for all of the main bands active in pyridine, and variations in position, half-height width and relative intensity were observed. The bands in the 3000 and 1000 cm −1 regions from pyridine on the several forms of silica, when considered in relation to parallel infra-red studies, can be interpreted in terms of an initially adsorbed species involving a strong hydrogen bond between surface OH groups and the pyridine nitrogen lone-pair. Physically adsorbed pyridine, with a spectrum similar to that of the pure liquid, occurs at higher coverage. Three species are observed from pyridine on BDH γ-alumina, two of them similar to those found on silica, and the third probably held to the surface by a coordinate linkage involving the nitrogen atom. Pyridine adsorbed on NaY zeolite appears to be held to the cationic sites. Raman spectra have been obtained by adsorption of a number of other molecules on porous glass, including benzene, methyl iodide, and several substituted benzenes. In the early stages of adsorption benzene and aniline gave spectra notably different from those of the pure liquids, and possibly attributable to species held to the surface through hydrogen-bonding involving surface OH groups.

Untersuchungen an Hämoprotein‐Modellen

In aqueous alkaline solution poly‐(N‐vinylimidazole) interacts with haemin to form two types of complexes. The molecular weight of the PVIm was about 12000 and the number of binding sites for haemin monomer varied between 8 to 17 per PVIm molecule in dependence on the pH. At pH &lt; 11.0 a red haemin‐PVIm complex is formed showing absorption maxima at 532 and 411 mμ and at pH &gt; 11.5 a green complex with maxima at 595, 578 and 391 mμ. At pH &lt; 9 the equilibrium between haemin and PVIm is nearly independent of pH but clearly dependent on the haemin concentration. This dependence as well as the asymmetry of the haemin‐PVIm association curves prove a dissociation of the haemin dimers into monomers in combining to PVIm. The spectral type of the red complex and the characteristics of the complex formation at pH &lt; 11 suggest a co‐ordinative interaction of one imidazole group of PVIm with the haemin iron. In the green compound above pH 11.5 there is no co‐ordinative linkage between PVIm imidazole residues and haemin iron or at most a very weak one. Complex formation between N‐ethylimidazole or N‐methylimidazole with haemin is mainly due to enthalpy changes whilst the combination of PVIm with haemin is mainly related to entropy effects. The free enthalpies of the formation of the co‐ordinative red haemin‐PVIm complex and the non‐co‐ordinative green complex do not differ significantly. The stability of the haemin‐PVIm complexes can therefore be attributed mainly to non‐co‐ordinative interactions between both partners, probably to hydrophobic bonding. The red haemin‐PVIm complex can bind one cyanide anion per haemin with high affinity. The spectrum of the resulting haemin‐PVIm‐cyanide complex shows absorption maxima at 542 and 419 mμ. Formation of the complex is independent of the pH, proving that the co‐ordinatively bound imidazole group is displaced from the iron by CN−. However, the haemin remains attached to the PVIm‐matrix. The differences in complex formation of haemin with monomeric imidazole derivatives and with PVIm are essentially due to the existence of multiple non‐co‐ordinative interactions between PVIm and haemin. There are some analogies between this binding and the multiple non‐co‐ordinative bonds between haemin and apolar amino acid residues in hemoglobins.

Studies of anhydrous metal nitrates. V. Vibrational spectra of In(NO3)3 and Pd(bipy)(NO3)2

The vibrational spectra of nitrato complexes and anhydrous covalent metal nitrates have been used to investigate the nature of the metal-ligand bond. Recent studies have cast some doubt on the unidentate-bidentate classification of nitrato coordination and indicate that in most cases two oxygen atoms are involved in each coordinate linkage. The vibrational frequencies observed for the salts are, however, still useful in giving crude information concerning the bonding involved. This note reports the spectra of two anhydrous salts and demonstrates how the data may be usefully interpreted.

Metal complexation kinetics of serine

Rate constants for the formation and dissociation of l-serine complexes of Ni(II), Co(II), Cu(II) and Zn(II) have been determined by the temperature-jump technique. For the overall reaction at 25° and I = 0.1 M, ML n−1 + L ⇌ k −n k n ML n (where M = Ni(II), Co(II), Cu(II) or Zn(II), L = anionic form of the ligand, n = 1, 2, or 3, and charges have been neglected), the results are: Ni(II), k 1 = 2.9·10 4 M −1·sec −1, k −1 = 0.11 sec −1, k 2 = 3.4·10 4 M −1·sec −1, k −2 = 1.6 sec −1, k 3 = 3.0·10 4 M −1·sec −1, k −3 = 28 sec −1; Co(II), k 1 = 2.0·10 6 M −1·sec −1, k −1 = 93 sec −1 k 2 = 2.0·10 6 M −1·sec −1, k −2 = 930 sec −1; Cu(II), k 1 = 2.5·10 9 M −1·sec −1, k 2 = 5.10 8 k −2 = 150 sec −1; Zn(II)_, k 1 approx. 1.10 8 M −1· sec t ̄ 1 approx. 2.10 3 sec − . These results are interpreted in terms of a mechanism in which the rate-determining step for complex formation is the loss of a water molecule from the metal ion's inner coordination sphere. (A possible exception is the reaction sifCuL + L ⇌ CuL 2, where changes in the metal ion's configuration may affect the forward rate.) All the dissociative rate constants appear to be influenced by the bond weakening effect of the β-hydroxyl group on the coordinate linkage.

Thermodynamics of pyridine and 1-alkyl-pyridinium complexes of protohaemin in aqueous solution.

1 In alkaline aqueous solution (pH > 10) protohaemin forms a green coloured pyridine complex containing two ligands per haemin dimer. The thermodynamics of this reaction is characterized by a considerable entropy change due to hydrophobic interactions between both partners. 2 Similar haemin complexes are formed by N-alkyl-pyridinium halides. The absorption spectra are nearly identical to those of the corresponding pyridine complexes although there is no possibility of interaction with the positively charged haemin iron. Pyridinium cations develop a higher affinity towards haemin than the neutral pyridines. This behaviour is attributed to electrostatic attractions between the propionylic groups of porphyrin and the positively charged pyridinium salts. 3 The introduction of methyl groups intensifies the haemin complex stability both of the pyridines and the pyridinium salts. In order of increasing methylation of the ligands the reaction entropy increases. 4 Following the substitution of pyridine in position 4 by a cyano group or following the transition from N-alkyl-pyridinium halides to N-alkyl-quinolinium halides the affinity towards haemin increases and the thermodynamics show a decrease of the reaction enthalpy whilst the entropy of the system changes only little. For this behaviour π-donor-acceptor interactions should be responsible. 5 The results demonstrate the contribution of several types of chemical bond in the reaction of protohaemin with ligands. Apart from the well investigated coordinative linkage to the iron atom, π-donor-acceptor and hydrophobic interactions between ligands and the porphyrin system as well as ionic bonds between the propionylic groups of the porphyrin and positively charged ligands contribute to their haemin complex formation. 6 The significance of the results is discussed with regard to the haemin-protein interaction in haemoproteins.

The binding of calcium and yttrium ions to a glycoprotein from bovine cortical bone

The binding of Ca(2+) and Y(3+) to an acidic glycoprotein from bovine cortical bone, bone sialoprotein, was determined from the titration curves at I 0.2 in the presence and absence of the cations. The binding of Y(3+) was greater than that of Ca(2+). The value for the association constant, k, for the interaction with Y(3+) increased with pH, from log k 2.93 at pH3.4 to log k 3.50 at pH4.4, and the number of binding sites/mol. increased from 4.6 at pH3.4 to 9.1 at pH4.4. It is proposed that the binding site consists of three carboxyl groups, but it is likely that the binding is a strong electrostatic interaction rather than a co-ordination linkage. A chondroitin sulphate-protein complex also extracted from bovine cortical bone interacted with Y(3+) and Ca(2+) to a similar extent as did bone sialoprotein. It is suggested that these materials are present in bone at the resting and resorbing surfaces and that they contribute to the deposition of yttrium, americium and plutonium at these sites.

The chemistry of poly(vinyl chloride) stabilization. IV. Organotin stabilizers having radioactively tagged tin atoms

AbstractThe chemistry of poly(vinyl chloride) stabilization by organotin compounds has been studied by the use of a radioactive tracer technique. The stabilizers studied were of the type [R2Sn Y2]n, where R was either butyl or octyl, Y either monomethyl maleate, oxooctylthioglycolate, or β‐mercaptopropanoate, and 113Sn was the radioactive tag. It was found that resins milled into films with the tagged stabilizers retain an appreciable amount of radioactivity after the films have been subjected to the conditions of accelerated thermal degradation, dissolution in tetrahydrofuran, and thereafter precipitated from solution by the addition of methanol. The amount of retained radioactivity varies with the duration of the heat treatment and with the nature of the Y group in a manner that parallels our findings in a previously reported study using a 14C tag in the stabilizers' butyl groups. We have also found that the amount of radioactivity retained by the precipitated resins decreases in a regular manner when the resins are subjected to a sequence of repeated dissolutions and precipitations. However, in the case of the resin stabilized with dibutyltin‐113Sn bis(monomethyl maleate) at least, the loss of radioactivity with repeated dissolution and precipitation appears to level off after 13–14 cycles and approach a constant value of retention. Treatment of the radioactive resins with anhydrous hydrogen chloride results in the loss of essentially all their radioactivity. On the basis of these findings, we suggest that in the performance of their stabilizing action, the organotin compounds undergo little or no cleavage of their carbon‐tin bonds. Further, the observed retention of radioactivity by the resin is best rationalized as due to the existence of a coordinative linkage formed between the stabilizer's tin atom and some donor atom present in polymer's molecular structure.

Brown Nitrosylpentamminechromium(III) Salts and Green Nitrosylpentamminechromium(III) Perchlorate

Abstract A new series of chromium ammines, i.e., nitrosylpentamminechromium(III) salts, were obtained by the reaction of an ammoniacal chromium(II) solution with sodium nitrite. The derivatives are usually reddish brown, but only the perchlorate is bright green. The infrared absorption spectra indicate that in the green perchlorate the rocking frequency of ligating ammonia is lower, while the stretching frequency of the nitrosyl group is higher than in the brown chloride. These results seem to show indirectly that the coordinate linkage is weaker in the green perchlorate.

Observations on a highly specific method for the histochemical detection of sulphated mucopolysaccharides, and its possible mechanisms

ABSTRACT Whereas basic dyes in aqueous solutions stain chromatin, all mucins, mast cells, the ground substance of cartilage, and epidermis, it has been shown that a 0·03 % solution of basic dye in 5% aluminium sulphate produces a highly specific staining reaction for sulphated mucopolysaccharides. The best dyes are nuclear fast red (Herzberg) and methylene blue. Acid dyes in solutions of aluminium salts are induced to stain the ground substance of cartilage. These observations have been confirmed in a number of species. Other metallic ions have similar properties and the use of green and purple chromic salts indicate that co-ordination plays a part in the reaction. Methylation, saponification, and sulphation experiments show that the sulphate group is essential. This has been confirmed by using pure chemical substances in gelatin models. Oxidation of keratin with performic acid, which produces sulphonic groups, causes hair (previously negative) to react. From this it is suggested that sulphonic groups may also react, and that the reactive groups need not be attached to mucopolysaccharides. It is further suggested that the specificity of sulphated mucopolysaccharides is due to the fact that they are the only substances present in the tissues with a sufficient concentration of sulphate groups. Experiments with solochrome azurine show that the aluminium is attached to all tissue elements irrespective of their nature. It is suggested by analogy with the work of others on the action of mordants that this attachment is by co-ordinate linkage. Acid dyes of strong and weak type buffered to a variety of pH levels show that ionization plays little if any part in the staining of the sulphated elements, but may be of considerable importance in the staining reactions of the other tissue elements. By analogy with solochrome azurine, which is known to co-ordinate with aluminium, it is suggested that the dye is attached, by means of a further co-ordinate bond, to the metal. It is suggested that the sulphate group may owe its specificity to its strongly acid character, and the fact that such groups are capable of forming extremely stable complexes with metallic ions. It is concluded that this is a highly specific method of staining sulphated mucopolysaccharides, depending upon the formation of a link by a metallic ion between the tissues and the dye, in the fashion of a true mordant. The ability of the dye to attach itself to the metallic ion depends finally upon the resultant of the electrostatic charges on the tissues and the metallic ion.

The cross-linking of conarachin II with metal salts

Conarachin II at μ = 0.5, pH 5.3, is cross-linked by Al +++, Fe +++, and Cr +++. No evidence of cross-linking has been observed with bivalent or quadrivalent ions under these conditions. With A1 +++ and Fe +++ the reaction occurred fairly rapidly, and the protein complexes were readily broken down by phosphate ions, indicating a salt linkage between the metal and the protein. The extent of cross-linking increased with increase in metal to protein ratio but decreased with increasing pH. With Cr +++ the complex formed more slowly and was stable to phosphate, indicating that coordinate linkages are probably involved. Fresh Cr +++ solutions were more effective than old ones. An anionic chromium complex gave similar results to those with chromic sulfate but with more pronounced cross-linking.