Bioenergetics and Linear Nonequilibrium Thermodynamics

Caplan, S. Roy; Essig, Alvin

doi:10.4159/harvard.9780674732063

Cited by 134 publications

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“…1,2) For the simplicity, we consider a transport system of hPEPT1 in which there are two driving forces, the electrochemical potential differences for substrate (X S ) and H ϩ (X H ϩ) and two fluxes, the substrate flux (J S ) and the proton flux (J H ϩ). According to the empirical evidence, 32,48) the flow is a linear function of the driving force over a relatively large range of flow and force, which correspond in the case of the present study to the flux and the electrochemical potential difference, respectively. Thus, we can express the relationship between flux and driving force as the following phenomenological equations 31,32,48) ; 49) According to Onsager's reciprocal relationship, 48) the matrix of coefficients for a system of flows and forces based on an appropriate dissipation function is symmetrical and the following equation holds;…”

Section: Discussionmentioning

confidence: 99%

“…The driving force is therefore composed of components of the proton-motive force and of the substrate gradient, and translocation of substrate will proceed until the sum of the electrochemical potential for substrate and proton is equal to that of the extracellular space. A general consideration of energy conversion from the viewpoint of the theory of nonequilibrium thermodynamics gives the following equation as to the permeability clearance for influx process 31,32) (see Appendix); (3) where PS inf and PS eff represent the permeability clearances for influx and efflux processes, respectively; R, T, F and Dj are gas constant, absolute temperature, Faraday's constant and membrane potential difference, respectively. DpH represents the difference of pH between intracellular and extracellular pH (pH in ϪpH ext ).…”

Section: Discussionmentioning

confidence: 99%

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The Extracellular pH Dependency of Transport Activity by Human Oligopeptide Transporter 1 (hPEPT1) Expressed Stably in Chinese Hamster Ovary (CHO) Cells: A Reason for the Bell-Shaped Activity versus pH

Fujisawa

Tateoka

Nara

et al. 2006

Biological & Pharmaceutical Bulletin

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It has been estimated that more than 80% of amino acids found in the intestinal lumen after a protein meal are in the form of small peptides rather than free amino acids.1) Therefore, a majority of protein digestion products are obligatorily absorbed via an intestine oligo-peptide transporter called PEPT1. Of interest, PEPT1 also mediates the absorption of a huge number of pharmacologically important compounds including peptidomimetic drugs, 2,3) such as oral b-lactam antibiotics, 4-6) ACE-inhibitors like captopril, 7) or the peptidase inhibitor bestatine 8) and even compounds without an obvious peptide bond or equivalent, 9) such as d-amino levulinic acid.10) This surprisingly high tolerance for structural diversity of the substrate by PEPT1 has been expected to be used as a channel to increase the intestinal absorption of poorly absorbable drugs. 11)The transport of substrates via PEPT1 is coupled to the downward movement of a proton in accordance with its electrochemical gradient. 2,3,12) It has been demonstrated in intestinal membrane vesicles, 4,13,14) Xenopus oocytes 15) and culture cells 16) that the transport activity of PEPT1 shows a bellshaped pH dependence with an optimal pH 5.5 to 6.0. This optimal pH is physiologically collaborated with an acidic unstirred water layer (pH 5.5-6.0) in the intestinal lumen. 1,17) Hence, PEPT1 can function most efficiently in epithelial cells of the small intestine.As for the bell-shaped activity of PEPT1 vs. pH, the reason why the transport activity decreases with an increase in pH is obviously the decrease in the driving force of the proton electrochemical potential gradient. On the other hand, why does the activity decrease in a more acidic region although the driving force should increase? To answer this question, we will try to obtain a relationship between the transport activity and extracellular pH. However, there is a problem to be solved: The driving force changes along with the change in extracellular pH. The pH-dependent properties of PEPT1 should be determined without changing the driving force. Here, we employ the experimental condition that the proton concentration gradient across the membrane is dissipated by the addition of monensin and nigericin 18,19) ; then the driving force is solely the membrane potential. To perform this experiment, a cell line is necessary which shows high transport activity. First, we established stably transfected CHO cells which show high transport activities for various substrates with almost the same K m values as those obtained from those of a model human intestine epithelial cell line, Caco-2. [20][21][22] Thus, this CHO cell line over-expressing hPEPT1 (designated as CHO/hPEPT1) is useful and convenient for transport studies of hPEPT1. In the present study, we then examined the pH-dependency of transport activity by hPEPT1 using CHO/hPEPT1 cells. Human oligopeptide transporter (hPEPT1) translocates di/tri-peptide by coupling to movement of proton down the electrochemical gradient. This transporter has the characteristics ...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

The Extracellular pH Dependency of Transport Activity by Human Oligopeptide Transporter 1 (hPEPT1) Expressed Stably in Chinese Hamster Ovary (CHO) Cells: A Reason for the Bell-Shaped Activity versus pH

Fujisawa

Tateoka

Nara

et al. 2006

Biological & Pharmaceutical Bulletin

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“…The most rigorous basis for developing a correlation for or even predicting thermodynamic efficiency factors is probably the linear energy transducer theory developed by Kedem and Caplan [58], Caplan and Essig [54], and Stucki [59] and reviewed by Gnaiger [60] and Westerhoff [61]. This theoretical development may be used to link practically important culture characteristics such as Y X=S and Á to fundamental parameters of irreversible thermodynamics.…”

Section: Prediction Based On Growth Efficiency Analysis and Irreversimentioning

confidence: 99%

“…To this effect, many different bioenergetic efficiency coefficients have been defined [40,[53][54][55][56], but it has been shown that many of these boil down to a so-called energy transducer efficiency characterizing the fraction of the Gibbs energy released by the driving reaction (a) that can be recovered in the form of Gibbs energy stored in the newly grown biomass [57]:…”

Section: Prediction Based On Growth Efficiency Analysis and Irreversimentioning

confidence: 99%

Biothermodynamics of live cells: a tool for biotechnology and biochemical engineering

Stockar

2010

Journal of Non-Equilibrium Thermodynamics

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The aim of this contribution is to review the application of thermodynamics to live cultures of microbial and other cells and to explore to what extent this may be put to practical use. A major focus is on energy dissipation effects in industrially relevant cultures, both in terms of heat and Gibbs energy dissipation. The experimental techniques for calorimetric measurements in live cultures are reviewed and their use for monitoring and control is discussed. A detailed analysis of the dissipation of Gibbs energy in chemotrophic growth shows that it reflects the entropy production by metabolic processes in the cells and thus also the driving force for growth and metabolism. By splitting metabolism conceptually up into catabolism and biosynthesis, it can be shown that this driving force decreases as the growth yield increases. This relationship is demonstrated by using experimental measurements on a variety of microbial strains. On the basis of these data, several literature correlations were tested as tools for biomass yield prediction. The prediction of other culture performance characteristics, including product yields for biorefinery planning, energy yields for biofuel manufacture, maximum growth rates, maintenance requirements, and threshold concentrations is also briefly reviewed.

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“…For them to occur it is necessary that they would be accordingly interconnected with spontaneous processes -such that follow a natural gradient. Coupled chemical reactions is an example (see Caplan, Essig, 1983): portion of free energy, "released" in spontaneous reactions, is "accumulated" in some other chemical processes, which otherwise do not proceed.…”

Section: Results and Hypothesismentioning

confidence: 99%

The Phenomenon of Biological Evolution: 19th Century Misconception

Balciunas¹

2009

SSRN Journal

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Abstract. Scientists still think that biological evolution is driven by the process named natural selection. Perhaps this 19th century notion was indeed a revolutionary idea at the time when it has been introduced. However, now it seems that natural selection hypothesis most probably is wrong. It does not explain, above all, why biological organization arise in the course of evolution. I show, on a rather abstract level of consideration, that exists another explanation why this intriguing phenomenon -life evolution -take place. Here it is argued that biological organization is solely a product of self-replication.

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Bioenergetics and Linear Nonequilibrium Thermodynamics

Cited by 134 publications

References 0 publications

The Extracellular pH Dependency of Transport Activity by Human Oligopeptide Transporter 1 (hPEPT1) Expressed Stably in Chinese Hamster Ovary (CHO) Cells: A Reason for the Bell-Shaped Activity versus pH

The Extracellular pH Dependency of Transport Activity by Human Oligopeptide Transporter 1 (hPEPT1) Expressed Stably in Chinese Hamster Ovary (CHO) Cells: A Reason for the Bell-Shaped Activity versus pH

Biothermodynamics of live cells: a tool for biotechnology and biochemical engineering

The Phenomenon of Biological Evolution: 19th Century Misconception

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