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The thermodynamic ionization constants (pKa) of indapamide, clonidine and methyldopa have been determined at 25 degrees C and 35 degrees C by pH titration technique. The pKa varies linearly with mole fraction of dioxane. The thermodynamic parameters have been calculated.
Thermodynamic approaches used in soil agrochemical studies allow to determine the direction of processes occurring in soils and to provide theoretically meaningful predictions of changes in ecosystems as a whole in response to various factors. Analysis of redox reactions of the NH4+ reversible NO3- equilibrium in agrocenoses of gray forest soil has shown that the additional introduction of nitrogen fertilizers is undesirable both from the economical and ecological points of view, since the dominating process occurring with the loss of nitrogen from the soil in the form of gaseous compounds is thermodynamically most preferred.
OBJECTIVE: To analyze the saturation degree of O2 in myoglobin and hemoglobin. METHOD: Analysis is based on thermodynamic concepts such as Gibbs free energy, entropy, internal energy and so on. RESULT: The analytical result were consistent with the results of experiments and analysis made by other authors. CONCLUSION: The thermodynamic method is feasible in analysing O2 saturation degree in myoglobin and hemoglobin.
The principle of charge transfer complexation involving a pi-acceptor (chloranilic acid) and an n-donor (chlorpheniramine) was utilized in the assay of the later in its pure form and in its tablet dosage forms. Some thermodynamic parameters of the complex such as association constant (Kc), molar absorptivity (epsilon c), free energy change (delta G degree), enthalpy (delta H degree) and entropy (delta S degree) changes were determined to establish the stability of the complex and the optimum conditions for the complex formation. The values obtained for these thermodynamic parameters indicated that the complex formed between this two chemical entities is highly stable. Assay of chlorpheniramine in its pure form and in its tablet dosage forms gave high percentage recoveries. The principle of charge transfer complexation could therefore be employed in the colorimetric assay of chlorpheniramine in its tablet dosage forms.
All the theories of carcinogenesis have properly described this event from methodologically different points of view (medical, biological, social, biochemical psychological etc.). The point is that one should understand the thermodynamical rules underlying each of these approaches. On this level of knowledge, quantum thermodynamics combines matter and energy, while technical quantization in a novel way differentiates precancerous states as the dissipathogenic ones from the neoplasms as the newly formed dissipative structures (systems). From the essential nature of the neoplasm one can derive some general rules of therapy which focus mainly on: 1 degrees prevention and therapy of the dissipathogenic states, 2 degrees strengthening of the regenerative and defensive mechanisms of the organism and, finally, 3 degrees removal of neoplastic changes as widely as necessary but also as sparingly as possible. For a long time, these rules have been observed in reverse order. That cannot improve the medical outcome, which has not changed for a few dozen years, i.e. recovery depending on the clinical level at the moment of the diagnosis.
The complex formation of the antibiotic mitoxantrone (novantrone) with the deoxytetranucleotide 5'-d(TpGpCpA) in an aqueous salt solution was studied by one- and two-dimensional (2D-TOSCY and 2D-NOESY) 1H NMR spectroscopy (500 MHz). Concentration and temperature dependence of proton chemical shifts of molecules were measured. On the basis of these data, the equilibrium constants of the reaction, the relative content of various complexes as a function of concentration and temperature, the limiting values of chemical shifts of novantrone in complexes, and the thermodynamic parameters delta H and delta S of complex formation of molecules were calculated. It was concluded that the attachment sites for novantrone are pyrimidine-purine nucleotide sequences, sites d(TG) and d(CA) of the tetranucleotide duplex. The analysis of the thermodynamic parameters of the complex formation suggests that intermolecular hydrogen bonds and electrostatic interactions of the aminoalkyl chains of novantrone with the duplex d(TpGpCpA)2 play an important role in the stabilization of complexes 1:2 and 2:2. The results were compared with those obtained earlier for typical intercalators of ethidium bromide and daunomycin under identical experimental conditions.
The Earth is an open thermodynamic system, that remains in a steady state far from the equilibrium, through energy and matter exchanges with the surrounding environment. These natural constraints, which prevent the system from maximizing its entropy, are threatened by human action and our ecosystem needs urgent protection. In this viewpoint the environmental certification was born, according to international standards ISO 14001, ISO 14040, and European Regulation EMAS. These are voluntary adhesions to a program of environmental protection by companies, administrations and organizations which, starting from the respect of the existing environmental laws and regulations, decide to further improve their environmental performance. To obtain and maintain certification of a system is necessary to apply some indicators to evaluate its environmental performance and to demonstrate its progressive improvement. Here we propose to use for this purpose the thermodynamic indicators produced from energy analysis by Odum. The case study is Montalcino city (Italy) and energy indicators are used to evaluate environmental performance of this system where exist different activities, from agricultural productions, to tourism. Results show that energy analysis could become a valid standard monitoring method for environmental certification, especially in consideration of its wide application field.
Temperature dependences of proton chemical shifts of the molecules in aqueous solutions of proflavine with deoxytetraribonucleoside triphosphates of different base sequence--5'-d(CGCG), 5'-d(GCGC), 5'-d(ACGT) and 5'-d(AGCT) have been studied by 500 MHz NMR spectroscopy. Methods of calculation of thermodynamical parameters of complex formation, giving an opportunity to differentiate the contributions of the reactions leading to the formation of different types of complexes in conditions of the composite equilibrium in solution, have been suggested. Enthalpies and entropies of the reactions of 1:1, 2:1, 1:2, 2:2 complexes formation between proflavine and tetranucleotides have been determined. Comparative analysis of the calculated thermodynamical parameters has been made and assumptions about the nature of intermolecular interactions responsible for the formation of dye complexes with different tetranucleotides have been proposed.
Light causes the all-trans to 13-cis isomerization of the retinal in bacteriorhodopsin; the thermal relaxation leading back to the initial state drives proton transport first via proton transfer between the retinal Schiff base and D85 and then between the Schiff base and D96. The reaction sequence and thermodynamics of this photocycle are described by measuring time-resolved absorption changes with a gated multichannel analyzer between 100 ns and 100 ms, at six temperatures between 5 degrees C and 30 degrees C. Analysis of the energetics of the chromophore reaction sequence is on the basis of a recently proposed model (Váró & Lanyi, Biochemistry 30, 5016-5022, 1991) which consists of a single cycle and many reversible reactions: BR -hv-->K<==>L<==>M1-->M2<==>N<==>O-->BR. The existence of the M1-->M2 reaction, which functions as the switch in the proton transfer, is confirmed by spectroscopic evidence. The calculated thermodynamic parameters indicate that the exchange of free energy between the protein and the protons is at the switch step. Further, a large entropy decrease at this reaction suggests a protein conformation change which will conserve delta G for driving the completion of the reaction cycle. The results provide insights to mechanism and energy coupling in this system, with possible relevance to the general question of how ion pumps function.
Oncology--just as every field of medicine that deals with etiology, diagnostics, pathomechanism and treatment of diseases--is only a part of the general human knowledge, whose all significant achievements must be used to protect human health. This pursuit has as its object not only the benefits form practical discoveries (L. Pasteur, W.C. Roentgen, P. Curie and M. Skłodowska-Curie, V. Schally etc.), but also theoretical generalizations (A. Einstein, W.K. Heisenberg and I. Prigogine). Unfortunately it is the lack and/or slow adaptation of that information, that is responsible for the still unsatisfactory progress in clinical oncology. Responsibility rests not only with oncologists, but primarily with editors of medical journals and textbooks, who have a moral duty to follow the entire general knowledge, especially in the field of the basic research. On the basis of an analysis of the contents of the Polish oncology textbooks and materials from the specialist conferences in gynaecologic oncology, they were found to: 1. Omit the current, particularly domestic literature, 2. Contain mostly works, whose conclusions are textbook information, 3. Rarely include studies in the area of medical thermodynamics, 4. Attempt to explain the effects of the modern technologies, e.g. fotodynamics or nanotechnology using theoretical generalizations which are inadequate for them, and 5. Disregard the rule primum non nocere not only in prevention but even in the treatment of neoplasms. Neoplastic disease has many conditionings and types because of the unique identity of the neoplasms which cause it and which are caused by universal and natural phenomena of the self-organizing dissipative structures. It requires not only early diagnosing but also causative treatment already in the precancerous states, which are better detected by modern methods based on the quantum thermodynamics (lasers, fotodynamics, nuclear magnetic resonance, genetic nanotechnology etc.).
Fully characterizing the interactions involving biomolecules requires information on the assembly state, affinity, kinetics, and thermodynamics associated with complex formation. The analytical technologies often used to measure biomolecular interactions include analytical ultracentrifugation (AUC), isothermal titration calorimetry (ITC), and surface plasmon resonance (SPR). In order to evaluate the capabilities of core facilities to implement these technologies, the Association of Biomolecular Resource Facilities (ABRF) Molecular Interactions Research Group (MIRG) developed a standardized model system and distributed it to a panel of AUC, ITC, and SPR operators. The model system was composed of a well-characterized enzyme-inhibitor pair, namely bovine carbonic anhydrase II (CA II) and 4-carboxybenzenesulfonamide (CBS). Study participants were asked to measure one or more of the following: (1) the molecular mass, homogeneity, and assembly state of CA II by AUC; (2) the affinity and thermodynamics for complex formation by ITC; and (3) the affinity and kinetics of complex formation by SPR. The results from this study provide a benchmark for comparing the capabilities of individual laboratories and for defining the utility of the different instrumentation.
The binding of alpha-, omega-amino acids, which are important effectors of human plasminogen activation, to the isolated kringle 4 (K4) peptide region of this protein has been investigated by high sensitivity titration calorimetry. The titration curve of the heat changes accompanying binding of the widely employed ligand, epsilon-aminocaproic acid (EACA), to K4 were deconvoluted to yield the following binding characteristics: n = 0.87 +/- 0.08 mol/mol; Ka = 3.82 +/- 0.37 x 10(4) M-1; delta H = -4.50 +/- 0.22 kcal/mol; delta S = 6.01 +/- 0.7 entropy units; and delta G = 6.29 +/- 0.06 kcal/mol. Here, both delta H and delta S provide the driving force of the interaction, with both hydrogen bonds and hydrophobic interactions, the latter which may result from an induced conformational change in K4 upon ligand binding, as well as possible alterations in peptide-bound water structure, providing the stabilizing forces for complex formation. The thermodynamic binding parameters were not greatly influenced by pH between the values of 5.5 and 8.2, suggesting that titratable groups on K4 in this pH region did not influence the binding. Investigations of the binding properties of structural analogues of EACA to K4 demonstrated that definable steric requirements existed for a maximal interaction, with spacing between the functional groups on EACA, as well as a hydrophobic region of this molecule, being important. This rapid and reliable method for measuring all thermodynamic parameters of formation of this complex at a given temperature can now be employed to investigate this important interaction with a wide variety of kringles and modified kringles to provide a more complete understanding of the necessary factors for this binding to occur.
We have investigated the thermodynamic properties of the binding of substrates and uptake blockers to the specific sites labeled with a tritiated dopamine uptake inhibitor (i.e., 1-[2-(diphenylmethoxy)ethyl]-4-(3-phenyl-2-propenyl)piperazine ([3H] GBR 12783) or [3H]mazindol) using striatal membrane preparations. Raising the incubation temperature from 0 degrees C to 25 degrees C or 37 degrees C resulted in an increase in the dissociation constant of both [3H]mazindol and [3H]GBR 12783 for their specific sites of binding present in membrane suspensions obtained from either rabbit or rat striatum. However, maximal concentrations of binding sites were not affected by temperature. At all tested temperatures, both substrates and carrier blockers competed with either [3H]mazindol or [3H]GBR 12783 in a monophasic fashion, with Hill coefficients close to unity. Raising the temperature induced little or no increase in inhibition constants (Ki) for substrates (Ki ratio 37/0 degrees C less than 2.5). This is consistent with the mild increase of the Michaelis constant of dopamine for the neuronal uptake system when the incubation temperature was raised from 12.5 to 37 degrees C (from 126 to 406 nM). In contrast, increasing the temperature resulted in a more important increase in the Ki of uptake inhibitors (33 greater than Ki ratio greater than 5). Thermodynamic calculations showed that the binding of substrates is generally characterized by a mild decrease in enthalpy (range, -2- -6 kcal/mol) associated with an increase in entropy, whereas binding of uptake inhibitors led to a decrease of both parameters.(ABSTRACT TRUNCATED AT 250 WORDS)
The electrical and chemical components of the electrochemical proton gradient of submitochondrial particles can be monitored simultaneously by continuously recording optical signals from the probes oxonol-VI and 9-aminoacridine. Either respiration or ATP hydrolysis causes a red shift in the absorption spectrum of oxonol-VI indicative of a membrane potential and a decrease of the fluorescence of 9-aminoacridine indicative of a pH gradient. The magnitude of the membrane potential and pH gradient formed by respiring submitochondrial particles can be modulated by the thermodynamic phosphorylation potential (deltaGp) of the adenine nucleotide system. deltaGp is the Gibbs free energy of ATP synthesis and is defined by the relationship deltaGp = -deltaG'o + RTln([ATP]/[ADP][Pi] where deltaG'o is the standard free energy of ATP hydrolysis. Increasing values of deltaGp cause an increase in the steady state magnitudes of both the membrane potential and pH gradient. Thermodynamic phosphorylation potential titration experiments indicate that the electrochemical proton gradient normally maintained by respiring submitochondrial particles has an energy equivalent to 10.5 to 10.9 kcal/mol.
The authors review the thermodynamic bases and physiological limitations of the applicability of thermal engines for driving artificial heart ventricles. Show that the thermodynamic characteristics of Stirling and Brighton cycles do not make it possible to effectively use cycle-based engines in the artificial heart. A steam engine operating in accordance with the Rankine cycle may be regarded as an optimum type engine for that purpose. Demonstrate that according to the rules of physiology, use should be made of a separate driving of artificial heart ventricles by two independently operating steam engines. Provide the characteristics of the Soviet artificial heart "MIKRON" acceptable for implantation into the orthotopic position.
We examined the flash photolysis of oxy complexes of sperm whale myoglobin (Mb) on the nanosecond time scale at ambient temperatures. In this time range, we can observe the geminate reaction of Mb with the O2 ligand existing in the protein matrix after the photodissociation from the heme iron. We found that the fraction of the geminate component to the total O2 photodissociation exhibited temperature dependences. The geminate fraction decreased with rising temperature, indicating that the protein fluctuation is enhanced at high temperature because of thermal agitation. However, the temperature-dependent behavior showed a break at 20 degrees C. Concerning the geminate O2 escaping reaction from the protein matrix to the solvent region, the activation energy above 20 degrees C (0.4 +/- 0.4 kcal/mol) is significantly lower than that below 20 degrees C (5.1 +/- 0.4 kcal/mol). Thermodynamic analysis on the basis of the transition state theory indicated that the O2 escaping reaction above 20 degrees C is entropy dominated whereas that below 20 degrees C is enthalpy dominated. The results were qualitatively compatible with the theoretical prediction by J. Kottalam and D. A. Case [1988) J. Am. Chem. Soc. 110, 7690-7697). Comparing the kinetic and thermodynamic process of the O2 geminate reaction among several Mbs, we concluded that the geminate O2 reaction with Mb is governed by the dynamic motion of the protein which is sensitively controlled by the static interaction of the heme moiety with the surroundings.
The temperature-jump (T-jump) method has been used to investigate the binding mechanism to calf-thymus DNA of ellipticine and some of its derivatives. The results show that the plant alkaloid, ellipticine, interacts with DNA at a unique intercalation site whereas most of its synthetic derivatives, such as ellipticinium, 9-hydroxy-ellipticinium and related alkyl-oxazolopyridocarbazoles recognize two distinct DNA sites. Parallel analysis of kinetic data and DNA lengthening abilities of these derivatives suggests that only one of these two DNA sites is an intercalation site. Owing to the determination of the genuine number of drug-DNA complexes (inferred from T-jump experiments) and with the results of thermodynamic investigations (Van't Hoff plots), further characterization of the molecular interactions involved in the binding process was proposed. Thus, the formation of the unique intercalation complex of ellipticine was found to be entropy driven whereas binding of drugs which recognize the second class of binding sites was essentially enthalpy driven. These different thermodynamic behaviors suggest that intercalation essentially results from hydrophobic solvent structure effects in contrast to the second binding mode which principally arises from hydrogen bonding interactions through DNA grooves.
The bicyclic colchicine analogue 2-methoxy-5-(2',3',4'-trimethoxyphenyl)-2,4,6-cycloheptatrien-1-on e (MTC) has been used to study the thermodynamics of specific ligand binding to the colchicine site of tubulin, employing isothermal reaction microcalorimetry. The binding of MTC to purified calf brain tubulin, in 10 mM sodium phosphate buffer, pH 7.0, is characterized by delta H degree = -19 +/- 1 kJ.mol-1, delta G degree = -31.8 +/- 0.6 kJ.mol-1, and delta S degree = 43 +/- 5 J.mol-1.K-1 at 298 K, with a slight variation in the temperature range from 283 to 308 K. The binding thermodynamics of colchicine and allocolchicine are similar to MTC under the conditions examined, suggesting related molecular interactions of the three ligands with the protein binding site. The standard enthalpy changes of binding of colchicine and MTC at 308 K coincide within experimental error. Therefore the more favorable free energy change of binding of colchicine must come from a larger binding entropy change (by about 20 J.mol-1.K-1). This difference could be attributed to the presence of the middle ring of colchicine, which is absent in MTC. Consistently, a similar entropy change is observed by the comparison of allocolchicine to MTC binding at several temperatures. In addition, allocolchicine binding is about 6 kJ.mol-1 less exothermic than MTC binding, which could be attributed to the presence in allocolchicine of a substituted phenyl ring instead of the colchicine-MTC tropolone ring. The present results and analysis are fully compatible with the previously proposed bifunctional binding of colchicine and MTC (through their trimethoxybenzene and tropolone moieties) to a bifocal protein binding site, and also with a partial immobilization of intramolecular rotation of MTC upon binding, which in colchicine is already constrained by its middle ring (Andreu, J. M., Gorbunoff, M. J., Lee, J. C., and Timasheff, S. (1984) Biochemistry 23, 1742-1752).