Vectorial processing

This specter should once and for all be laid to rest. The Curie principle as it applies to the system at hand (I will not state it in its most general form) forbids, in the linear regime, coupling between a vectorial process such as a flow and a scalar process such as a chemical reaction in an isotropic space. However, active transport does not occur in an isotropic or symmetrical system. Clearly, the protein constituting the pump is uniquely oriented within the membrane. 

Photoprotonic signals can be generated by light induced proton release, this might happen for the quaternary N-R+ derivatives of 117, for instance [8.233]. The photoproduction of proton gradients across membranes could serve as a light-powered proton pump for inducing vectorial processes such as the transport of protons [8.233, 8.234] or H+-ATPase model reactions [8.274]. 

Jencks, W.P. (1989a). Utilization of binding energy and coupling rules for active transport and other vectorial processes. Methods in Enzymol. 171,145-164. 

A protein engaged in the transport of a specific solute across a membrane must have two properties (1) the ability to bind the solute and (2) the ability to carry out a vectorial process, i.e., a directional process which delivers the solute from one side of the membrane to the other. 

Question What are some simple means by which the vectorial process might occur ... 

The phenomenological coefficients are important in defining the coupled phenomena. For example, the coupled processes of heat and mass transport give rise to the Soret effect (which is the mass diffusion due to heat transfer), and the Dufour effect (which is the heat transport due to mass diffusion). We can identify the cross coefficients of the coupling between the mass diffusion (vectorial process) and chemical reaction (scalar process) in an anisotropic membrane wall. Therefore, the linear nonequilibrium thermodynamics theory provides a unifying approach to examining various processes usually studied under separate disciplines. 

Equation (3.152) represents the entropy production for vectorial processes of heat and mass transfer. In Eq. (3.152), the conduction energy flow can be replaced by the heat flow J" using Eq. (3.140) and the total potential fi comprising the chemical potential and the potential energy per unit mass of component i /jl /x, i epi where Vep, = F,. 

Notice that, formally, the possibility of this conjunction violates the Curie principle, which forbids the conjunction of a scalar process (synthe sis of a substance) and a vectorial process (the proton transport through the membrane). Nevertheless, this contradiction is avoided due to the pres ence of a special conjugation tool like an anisotropic membrane. 

Five of the eight subunits of photosystem II reaction center are synthesized on chloroplast ribosomes. The three Tris-soluble subunits are synthesized on cytoplasmic ribosomes as larger precursors and are transported into the chloroplast by a vectorial processing mechanism [29, 119-121,133]. The genes coding for all the... 

Classification of mechanisms might help to understand complicated processes, but quite often it might be misleading. There are many exceptions to each of the proposed mechanisms, and one can always criticize a proposed mechanism on the grounds of these exceptions. Therefore, playing the devil s advocate, we shall classify the process of protein biogenesis in membranes into three mechanisms vectorial translation, vectorial processing and protein incorporation. 

Vectorial processing [4,33,34]. The polypeptides are usually made on free polysomes. The transport of the polypeptide chain across the membrane is independent of protein synthesis. In most of the cases the protein is synthesized as a larger precursor, and the completed polypeptide chain is present and even might be accumulated in the compartment where it is synthesized. Addition of protein synthesis inhibitors will not prevent the transport of the completed chains across the membrane. During or immediately after transport across the membrane, chemical... 

Vectorial processing — import of proteins into chloroplasts and mitochondria... 

We must realize at this point that the calorimetric technique entirely builds upon the establishment of equilibrium conditions enabling the use and help from equilibrium thermodynamics. Many facets of supramolecular chemistry, however, do not comply with this prerequisite. Molecular recognition, for instance, in particular as a crucial property of all living matter, which exists because of nonequilibrium conditions, must be considered a process that relies on kinetic selechvity and thus per se is not open to an all-encompassing description of the phenomenon using this technique [12]. Similar arguments limit the utility of calorimetry in other vectorial processes like membrane transport, signaling, catalysis or locomotion. Never-... 

While the conversion of a supramolecular complex back into its constituent components is part of the equilibration process and, as such, is contained in thermodynamic selectivity, any alternative transformation leading to a function is characterized by a rate and a corresponding monomolecular rate constant. Principally, it can refer to just one elementary reaction yielding the function, but more likely, function generation will be composed of several successive steps. In any case, a pathway is defined that features a certain activation barrier that, in turn, determines the total flux on this route. Typical kinetically controlled vectorial processes include the transport of compounds across membranes, the photosynthetic elec-... 

Oxidative phosphorylation in mitochondria is coupled to ion-transport. This is a system of coupled processes and not an individual chemical reaction. It provides an example of coupling of scalar and vectorial process. 

The Markovian property of vectorial processes can be lost by reducing the dimensionality of the process. One cannot expect that the knowledge of only a few components is again sufficient to predict the future probability (van Kampen, 1981, p. 80). 

At this point it is pertinent to note that with the introduction of geometric variables, the necessary degrees of freedom in process design are appearing. For the remainder it is convenient to introduce a new variable, K, which is the product of the phenomenological constant L and the relevant geometric variable. So for vectorial processes K is defined as ... 

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