Biomechanical and functional effects of shoulder kinesio taping® on cerebral palsy children interacting with virtual objects.

The reaching of objects is usually practiced by CP children in conventional or Virtual Reality-based therapies to enhance motor skill performance. Recently, Kinesio Taping® method has been studied to increase mechanical stability and improve functional movement of the upper limb; however, its influence on CP children´s upper limb motion has been rarely quantified due to lack of sensory measurement. Therefore, in this paper, we evaluate the biomechanical and functional effects of applying shoulder Kinesio Taping® on CP children in the reaching-transporting of virtual objects, by using a low-cost tracking device, exact robust differentiation of data and a simple nonlinear biomechanical dynamic model of the trunk and arm.

Human galectin-3 selective and high affinity inhibitors. Present state and future perspectives.

Over the last decade an increasing number of studies have been published reporting on the inhibitory potency or selectivity that several types of ligands show against human galectin-3 (hGal-3). The reason for this interest lies in the many important roles galectins play both in intra and extra-cellular functions. Among galectins, galectin-3 stands out because it is the only known member of its subfamily in mammals, is small and monomeric but capable of aggregating, and is known to be involved in a large number of disease processes, from cancer to heart failure. These characteristics and roles make hGal-3 an ideal target for drugs. Since it binds ß-galactosides, like the rest of the galectin family of proteins, the search and design of potent and at the same time selective inhibitors for it is not an easy task. Herein we discuss the chemical features of the most potent inhibitors described so far, as well as the structural basis of their exhibited selectivity, in order to shed light on the rational design of drugs against this target.

Binding affinity properties of dendritic glycosides based on a beta-cyclodextrin core toward guest molecules and concanavalin A.

The inclusion behavior and concanavalin A binding properties of hepta-antennated and newly synthesized tetradeca-antennated C-6-branched mannopyranosyl and glucopyrannosyl cyclomaltoheptaose (beta-cyclodextrin) derivatives have been evaluated by isothermal titration microcalorimetry and enzyme-linked lectin assay (ELLA), respectively. The synthesis of three first-order dendrimers based on a beta-cyclodextrin core containing 14 1-thio-beta-D-glucose, 1-thio-beta-mannose, and 1-thio-beta-rhamnose residues was performed following a convergent approach and involving (1) preparation of a thiolated bis-branched glycoside building block and (2) attachment of the building block onto heptakis(6-deoxy-6-iodo)-beta-cyclodextrin. Calorimetric titrations performed at 25 degrees C in buffered aqueous solution (pH 7.4) gave the affinity constants and the thermodynamic parameters for the inclusion complex formation of these beta-cyclodextrin derivatives with guests sodium 8-anilino-1-naphthalensulfonate (ANS) and 2-naphthalenesulfonate. The host capability of the persubstituted beta-cyclodextrins decreased with respect to the native beta-CD when sodium 2-naphthalenesulfonate was used as a guest and improved when ANS was used as a guest molecule. Heptavalent mannoclusters based on beta-CD cores enhance the lectin binding affinity due to the cluster effect; however, the increase of the valency from 7 to 14 ligands did not contribute to the improvement of the concanavalin A binding affinity. In addition, the synthesized hyperbranched mannoCDs lost completely the capability as a host molecules.

Thermodynamic analysis of the binding of glutathione to glutathione S-transferase over a range of temperatures.

The binding properties of a glutathione S-transferase (EC 2.5.1.18) from Schistosoma japonicum to substrate glutathione (GSH) has been investigated by intrinsic fluorescence and isothermal titration calorimetry (ITC) at pH 6.5 over a temperature range of 15-30 degrees C. Calorimetric measurements in various buffer systems with different ionization heats suggest that protons are released during the binding of GSH at pH 6.5. We have also studied the effect of pH on the thermodynamics of GSH-GST interaction. The behaviour shown at different pHs indicates that at least three groups must participate in the exchange of protons. Fluorimetric and calorimetric measurements indicate that GSH binds to two sites in the dimer of 26-kDa glutathione S-transferase from Schistosoma japonicum (SjGST). On the other hand, noncooperativity for substrate binding to SjGST was detected over a temperature range of 15-30 degrees C. Among thermodynamic parameters, whereas DeltaG degrees remains practically invariant as a function of temperature, DeltaH and DeltaS degrees both decrease with an increase in temperature. While the binding is enthalpically favorable at all temperatures studied, at temperatures below 25 degrees C, DeltaG degrees is also favoured by entropic contributions. As the temperature increases, the entropic contributions progressively decrease, attaining a value of zero at 24.3 degrees C, and then becoming unfavorable. During this transition, the enthalpic contributions become progressively favorable, resulting in an enthalpy-entropy compensation. The temperature dependence of the enthalpy change yields the heat capacity change (DeltaCp degrees ) of -0.238 +/- 0.04 kcal per K per mol of GSH bound.

A calorimetric study of the binding of S-alkylglutathiones to glutathione S-transferase.

The binding of three competitive glutathione analogue inhibitors (S-alkylglutathione derivatives) to glutathione S-transferase from Schistosoma japonicum, SjGST, has been investigated by isothermal titration microcalorimetry at pH 6.5 over a temperature range of 15--30 degrees C. Calorimetric measurements in various buffer systems with different ionization heats suggest that no protons are exchanged during the binding of S-alkylglutathione derivatives. Thus, at pH 6.5, the protons released during the binding of substrate may be from its thiol group. Calorimetric analyses show that S-methyl-, S-butyl-, and S-octylglutathione bind to two equal and independent sites in the dimer of SjGST. The affinity of these inhibitors to SjGST is greater as the number of methylene groups in the hydrocarbon side chain increases. In all cases studied, Delta G(0) remains invariant as a function of temperature, while Delta H(b) and Delta S(0) both decrease as the temperature increases. The binding of three S-alkylglutathione derivatives to the enzyme is enthalpically favourable at all temperatures studied. The temperature dependence of the enthalpy change yields negative heat capacity changes, which become less negative as the length of the side chain increases.

Influence of dynamic power compensation in an isothermal titration microcalorimeter.

A theoretical analysis in Laplace's transformed domain based on a power balance represents a suitable model for an isothermal titration calorimeter with dynamic power compensation, designed and implemented in our laboratory. A rigorous calibration of the injection system and the calorimetric response was also made. Using electrically generated heat pulses, two different time constants have been determined from the calorimetric transfer function and assigned to the physical parts of the calorimeter. The same was done for a protein-ligand interaction. The binding of 2'-CMP to ribonuclease A at low and high ionic strengths was used to check the apparatus and the results were compared with those obtained by other authors (Wiseman, T.; Williston, S.; Brandts, J.F.; Lung-Nan, L. Anal. Biochem. 1989, 179, 131-137). In this case, the analysis showed a different time constant for the heat source. Independently of the nature of the heat source, the calorimetric time constants obtained while working under compensation are always smaller than those corresponding to a noncompensated system. The improvement of the calorimetric response introduced by dynamic power compensation is thus explained in terms of the reduction of the time constants characteristic of the calorimeter. This theoretical model can be used to predict the shape of the thermogram for any given reaction of either known or supposed thermodynamic parameters. Therefore, the calorimetric study is extended to the other nucleotides, 2'-UMP and 5'-dUMP, which have not hitherto been reported in the literature.

Enthalpy of captopril-angiotensin I-converting enzyme binding.

High-sensitivity titration calorimetry is used to measure changes in enthalpy, heat capacity and protonation for the binding of captopril to the angiotensin I-converting enzyme (ACE; EC 3.4.15.1). The affinity of ACE to captopril is high and changes slightly with the pH, because the number of protons linked to binding is low. The determination of the enthalpy change at different pH values suggests that the protonated group in the captopril-ACE complex exhibits a heat protonation of approximately -30 kJ/mol. This value agrees with the protonation of an imidazole group. The residues which may become protonated in the complex could be two histidines existing in two active sites, which are joined to the amino acids coordinated to Zn2+. Calorimetric measurements indicate that captopril binds to two sites in the monomer of ACE, this binding being enthalpically unfavorable and being dominated by a large positive entropy change. Thus, binding is favored by both electrostatic and hydrophobic interactions. The temperature dependence of the free energy of binding deltaG degrees is weak because of the enthalpy-entropy compensation caused by a large heat capacity change, deltaCp =-4.3+/-0.1 kJ/K/mol of monomeric ACE. The strong favorable binding entropy and the negative deltaCp indicate both a large contribution to binding due to hydrophobic effects, which seem to originate from dehydration of the ligand-protein interface, and slight conformational changes in the vicinity of the active sites.

Calorimetric analysis of lisinopril binding to angiotensin I-converting enzyme.

Isothermal titration microcalorimetry has been used to measure changes in enthalpy and heat capacity for binding of lisinopril to the angiotensin I-converting enzyme (ACE; EC 3.4.15.1) and to its apoenzyme at pH 7.5 over a temperature range of 15-30 degrees C. Calorimetric measurements indicate that lisinopril binds to two sites in the monomer of both holo- and apo-ACE. Binding of lisinopril to both systems is enthalpically unfavorable and, thus, is dominated by a large positive entropy change. The enthalpy change of binding is strongly temperature-dependent for both holo- and apo-ACE, arising from a large heat capacity change of binding equal to -2.4 +/- 0.2 kJ/K/mol of monomeric holo-ACE) and to -1.9 +/- 0.2 kJ/K/mol of monomeric apo-ACE), respectively. The negative values of deltaCp for both systems are consistent with burial of a large non-polar surface area upon binding. Although the binding of lisinopril to holo- and apo-ACE is favored by entropy changes, this is more positive for the holoenzyme. Thus, the interaction between Zn2+ and lisinopril results in a higher affinity of the holoenzyme for this drug due to a more favorable entropic contribution.

Thermodynamic characterization of the binding of dCMP to the Asn229Asp mutant of thymidylate synthase.

Isothermal titration microcalorimetry and equilibrium dialysis have been used to characterize the binding of 2'-deoxycytidine 5'-monophosphate (dCMP) to the Asn229Asp mutant of Lactobacillus casei recombinant thymidylate synthase at pH 7.4 over a temperature range of 15 degrees C to 35 degrees C. Equilibrium dialysis analysis shows that dCMP binds to two sites in the dimer of both wild-type and mutant thymidylate synthase. A concomitant net uptake of protons with binding of dCMP to both enzymes, was detected carrying out calorimetric experiments in various buffer systems with different heats of ionization. The change in protonation for binding of dCMP to wild-type enzyme is lower than that obtained for binding of this nucleotide to TS N229D, which suggests that the pK value of Asp-229 is increased upon dCMP binding to the mutant enzyme. At 25 degrees C, although the binding of dCMP to wild-type and N229D TS is favoured by both enthalpy and entropy changes, the enthalpy change is more negative for the mutant protein. Thus, the substitution of Asn 229 for Asp results in a higher affinity of TS for dCMP due to a more favourable enthalpic contribution. The Gibbs energy change of binding of dCMP to the mutant enzyme is weakly temperature-dependent, because of the enthalpy-entropy compensation arising from a negative heat capacity change of binding equal to -0.83 +/- 0.02 kJ K(-1) per mol of dCMP bound.

Thermodynamic characterization of 5'-AMP binding to bovine liver glycogen phosphorylase a.

The binding of adenosine 5'-monophosphate to liver glycogen phosphorylase a (EC 2.4.1.1) has been studied by size exclusion high performance liquid chromatography and isothermal titration microcalorimetry at pH 6.9 over a temperature range of 25 to 35 degrees C. The results are compared with those of the binding of the same nucleotide to the muscle isozyme and to liver phosphorylase b. Calorimetric measurements in various buffer systems with different ionization heats suggest that protons are released during the binding of the nucleotide. The dimer of liver glycogen phosphorylase a has been shown to have two equal and independent sites for 5'-AMP, which would correspond to the activator sites identified in the muscle isozyme. The binding constants as well as the changes in Gibbs energy, enthalpy, and entropy per site for 5'-AMP binding were calculated at each temperature. The results show that the major contribution to the negative value of DeltaG0 stems from the value of DeltaH in the range of 25 to 35 degrees C. The enthalpy change of binding is strongly temperature-dependent, arising from a large negative DeltaCp of binding equal to -1.45 +/- 0.02 kJ K-1 (mol of 5'-AMP bound)-1, which suggests significant changes in the polar and apolar surfaces accessible to the solvent.

A calorimetric study of the binding of AMP to liver glycogen phosphorylase b.

The energetics of the interaction between liver glycogen phosphorylase b and the adenosine 5'-monophosphate (AMP) have been studied by equilibrium dialysis and isothermal titration calorimetry (ITC) at 25 degrees C. A concomitant net release of protons with AMP to phosphorylase binding was detected carrying out calorimetric experiments in three buffers having different heats of ionization at 25 degrees C. Four binding sites were found for AMP in the dimeric enzyme, which would correspond to the activator and the inhibitor sites identified in the muscle isozyme. The affinity of AMP for these four sites is similar. Thus, the binding of AMP to the activator sites seems to be non-cooperative and it does not perform the conformational change necessary to activate the enzyme. Moreover, the inhibitor sites are occupied almost in the same extension that the activator sites, which would impair any activation of the enzyme.

Thermodynamic analysis of the binding of 5-fluoro-2'-deoxyuridine 5'-monophosphate to thymidylate synthase over a range of temperatures.

The binding of 5-fluoro-2'-deoxyuridine 5'-monophosphate (FdUMP) to Lactobacillus casei recombinant thymidylate synthase has been studied by isothermal titration microcalorimetry at pH 7.1 over the temperature range 16-35 degrees C. Calorimetric measurements in various buffer systems with different heats of ionization suggest that a proton uptake is involved in the binding process of the nucleotide. In the temperature range investigated, the mol protons bound/mol nucleotide increases as the temperature decreases. A model of two equal and independent sites fits well with the binding isotherms for thymidylate synthase. The binding constants, the changes in Gibbs energy, enthalpy, and entropy/site for FdUMP binding were calculated at each temperature. The results show that the binding is driven by both enthalpy and entropy contributions in the range 16-35 degrees C. The enthalpy changes become more negative as the temperature increases, with delta Cp = -170 +/- 20 J.K-1.(mol FdUMP bound)-1. The behavior of the system supports the observation that FdUMP binds to thymidylate synthase without producing profound conformational changes in the protein dimer.