THE MAXIMUM EFFICIENCY OF PHOTOSYNTHESIS *

Within the ideal assumptions: (1) two Photosystems for photosynthetic fixation of CO₂, (2) all solar photons with Λ≥ 700 nm are absorbed, (3) the photon requirement is 8 for each CO₂ molecule fixed and O₂ molecule evolved and (4) the principal stable product of photosynthesis is d-glucose, the theoretical maximum efficiency of conversion of light to stored chemical energy in green-plant type (oxygen-evolving) photosynthesis in bright sunlight is calculated to be 13.0%. Thermodynamic arguments are presented which indicate that a photosynthetic system with one Photosystem would be highly unlikely to be able to drive each electron from water to evolve O₂ and reduce CO₂. The practical maximum efficiency of photosynthesis under optimum conditions is estimated to be 8–9%.     

Approximation methods in the computer numerically controlled fabrication of optical surfaces, Part 2: mollifications

The process of grinding and polishing optical surfaces usinga Computer Numerically Controlled machine produces a machinematerial removal profile. The profiles achievable by the machinedepend on the nature of the tool used in the process, and thetool center motions. In this paper machine material removalprofiles are developed as mollifications of given workpieceprofiles for a variety of tool configurations. The form of themollilication, in effect, defines the tool center motion. Convergenceof the machine's material removal profile to the given workpieceprofile as the support of the tool goes to zero is establishedunder mild assumptions. Numerical examples are included. This work supported in part by AFOSR Grant No. AFOSR 900094.     

Approximation Methods in the Computer Numerically Controlled Fabrication of Optical Surfaces, Part 1: Finite Dimensional Material Removal Profile Spaces

An analysis of the process of grinding and polishing of lensesand mirrored surfaces using a computer numerically controlledmachine is presented. This analysis provides the motivationfor the study of L₁ approximation of continuous functions bynonstandard approximants. Under suitable conditions, L₁ convergenceis established for a space of material removal profiles basedon a piecewise continuous material removal rate. A linear programmingalgorithm is used to find the best discrete L₁ approximation.Numerical examples are included.     

An Implicit Matching Principle for Global Element Calculations

A variational method is described which allows elliptic boundaryvalue problems with complex domains to be solved as a set ofcoupled problems over simple subdomains (global elements); thetrial functions used need not satisfy any of the boundary conditions. For smooth problems the method retains the rapid convergenceof the global variational approach; a major advantage howeveris that rapid convergence should also be attainable for singularproblems. In many cases the method will be simpler to use thanthe finite element method.     

Stability of Adams-Type Formulae for Second-Order Ordinary Differential Equations

The stability of methods for systems of second-order equationsis discussed. Stability regions are obtained for a single equationand the existence of stable step-sizes is shown for systems.An example is used as an illustration of the effect of the usualorder selection strategies on stability and accuracy.     

ChemInform Abstract: Binding of Nitric Oxide to First-Transition-Row Metal Cations: An ab initio Study

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Analysis of Stepsize Selection Schemes for Runge-Kutta Codes

Conditions on Runge-Kutta algorithms can be obtained which ensuresmooth stepsize selection when stability of the algorithm isrestricting the stepsize. Some recently derived results areshown to hold for a more general test problem.     

COMPARISON OF PHOTOTRAP COMPLEXES FROM CHROMATOPHORES OF RHODOSPIRILLUM RUBRUM, RHODOPSEUDOMONAS SPHEROIDES, AND THE R-26 MUTANT OF RHODOPSEUDOMONAS SPHEROIDES*

Abstract— After dissolution of the membrane structure of chromatophores from Rhodospirillum rubrum, Rhodopseudomonas spheroides , and the R-26 mutant of Rhodopseudomonas spheroides , active phototrap complexes from each have been purified by a column electrophoresis procedure. Phospholipids and transition metals were well separated from the phototrap complex in all three systems. The purified R. rubrum phototrap complex retained a full complement of antenna bacteriochlorophyll and carotenoid pigments which had nearly the same absorbance spectra as in the intact cell, and which delivered absorbed light energy to the phototrap with just as high efficiency as in the intact cell. Sodium dodecyl sulfate (SDS) disc gel electrophoresis using Tris buffer showed that these preparations often contained only two prominent polypeptides of 30,000 ± 2000 and 12,000 ± 4000 mol. wt., and a lesser amount of a third polypeptide of 21,000 ± 2000 mol. wt.
The phototrap complexes prepared from the wild type and the R-26 mutant of R. spheroides were similar, in that a partial separation from antenna pigments occurred during column electrophoresis. Both complexes had prominent polypeptides of 24,000 ± 2000 and 21,000 ± 2000 mol. wt., but no polypeptide of 30,000 mol. wt remained after electrophoresis. A third major polypeptide occurred with a mol. wt. of about 12,000 but seemed identifiable with an incompletely separated antenna pigment fraction. The phototrap complex prepared from the R-26 mutant had a typical reaction center spectrum.
In the case of wild type R. spheroides purification, two distinct protein-pigment complexes separated. Although the absorbance of the bacteriochlorophyll and carotenoid pigments were little changed from those of the in vivo system, different polypeptides in the two fractions were observed by SDS disc gel electrophoresis; only one fraction seemed to be intimately related with the phototrap complex.