Mn-porphyrins in a four-helix bundle participate in photo-induced electron transfer with a bacterial reaction center.

Hybrid complexes incorporating synthetic Mn-porphyrins into an artificial four-helix bundle domain of bacterial reaction centers created a system to investigate new electron transfer pathways. The reactions were initiated by illumination of the bacterial reaction centers, whose primary photochemistry involves electron transfer from the bacteriochlorophyll dimer through a series of electron acceptors to the quinone electron acceptors. Porphyrins with diphenyl, dimesityl, or fluorinated substituents were synthesized containing either Mn or Zn. Electrochemical measurements revealed potentials for Mn(III)/Mn(II) transitions that are ~ 0.4 V higher for the fluorinated Mn-porphyrins than the diphenyl and dimesityl Mn-porphyrins. The synthetic porphyrins were introduced into the proteins by binding to a four-helix bundle domain that was genetically fused to the reaction center. Light excitation of the bacteriochlorophyll dimer of the reaction center resulted in new derivative signals, in the 400 to 450 nm region of light-minus-dark spectra, that are consistent with oxidation of the fluorinated Mn(II) porphyrins and reduction of the diphenyl and dimesityl Mn(III) porphyrins. These features recovered in the dark and were not observed in the Zn(II) porphyrins. The amplitudes of the signals were dependent upon the oxidation/reduction midpoint potentials of the bacteriochlorophyll dimer. These results are interpreted as photo-induced charge-separation processes resulting in redox changes of the Mn-porphyrins, demonstrating the utility of the hybrid artificial reaction center system to establish design guidelines for novel electron transfer reactions.

Identification of amino acid residues in a proton release pathway near the bacteriochlorophyll dimer in reaction centers from Rhodobacter sphaeroides.

Insight into control of proton transfer, a crucial attribute of cellular functions, can be gained from investigations of bacterial reaction centers. While the uptake of protons associated with the reduction of the quinone is well characterized, the release of protons associated with the oxidized bacteriochlorophyll dimer has been poorly understood. Optical spectroscopy and proton release/uptake measurements were used to examine the proton release characteristics of twelve mutant reaction centers, each containing a change in an amino acid residue near the bacteriochlorophyll dimer. The mutant reaction centers had optical spectra similar to wild-type and were capable of transferring electrons to the quinones after light excitation of the bacteriochlorophyll dimer. They exhibited a large range in the extent of proton release and in the slow recovery of the optical signal for the oxidized dimer upon continuous illumination. Key roles were indicated for six amino acid residues, Thr L130, Asp L155, Ser L244, Arg M164, Ser M190, and His M193. Analysis of the results points to a hydrogen-bond network that contains these residues, with several additional residues and bound water molecules, forming a proton transfer pathway. In addition to proton transfer, the properties of the pathway are proposed to be responsible for the very slow charge recombination kinetics observed after continuous illumination. The characteristics of this pathway are compared to proton transfer pathways near the secondary quinone as well as those found in photosystem II and cytochrome c oxidase.

A bound iron porphyrin is redox active in hybrid bacterial reaction centers modified to possess a four-helix bundle domain.

In this paper we report the design of hybrid reaction centers with a novel redox-active cofactor. Reaction centers perform the primary photochemistry of photosynthesis, namely the light-induced transfer of an electron from the bacteriochlorophyll dimer to a series of electron acceptors. Hybrid complexes were created by the fusion of an artificial four-helix bundle to the M-subunit of the reaction center. Despite the large modification, optical spectra show that the purified hybrid reaction centers assemble as active complexes that retain the characteristic cofactor absorption peaks and are capable of light-induced charge separation. The four-helix bundle could bind iron-protoporphyrin in either a reduced and oxidized state. After binding iron-protoporphyrin to the hybrid reaction centers, light excitation results in a new derivative signal with a maximum at 402 nm and minimum at 429 nm. This signal increases in amplitude with longer light durations and persists in the dark. No signal is observed when iron-protoporphyrin is added to reaction centers without the four-helix bundle domain or when a redox-inactive zinc-protoporphyrin is bound. The results are consistent with the signal arising from a new redox reaction, electron transfer from the iron-protoporphyrin to the oxidized bacteriochlorophyll dimer. These outcomes demonstrate the feasibility of binding porphyrins to the hybrid reaction centers to gain new light-driven functions.

My Teaching Partner-Secondary: A video-based coaching model.

In the My Teaching Partner (MTP) program, coaches engage teachers in six to nine coaching cycles across a school year. Guided by the program's theory, coaches help teachers reflect on the emotional, organizational, and instructional features of classrooms. MTP was originally developed for Pre-K and early elementary classrooms (MTP Pre-K), but the current paper focuses on the secondary school version of this program, MTP-Secondary (MTP-S), given the need for coaching models with middle and high school teachers. The paper presents the guiding theory of MTP-S and how it relates to key components of the coaching cycle. We then offer a brief synthesis of research demonstrating its effectiveness in raising achievement, promoting positive peer interactions, and reducing racial disparities in teachers' discipline practices. We provide ideas for future research that would help advance theory on the essential components of effective coaching programs in secondary schools.

Electronic structure of the Mn-cofactor of modified bacterial reaction centers measured by electron paramagnetic resonance and electron spin echo envelope modulation spectroscopies.

The electronic structure of a Mn(II) ion bound to highly oxidizing reaction centers of Rhodobacter sphaeroides was studied in a mutant modified to possess a metal binding site at a location comparable to the Mn4Ca cluster of photosystem II. The Mn-binding site of the previously described mutant, M2, contains three carboxylates and one His at the binding site (Thielges et al., Biochemistry 44:389-7394, 2005). The redox-active Mn-cofactor was characterized using electron paramagnetic resonance (EPR) and electron spin echo envelope modulation (ESEEM) spectroscopies. In the light without bound metal, the Mn-binding mutants showed an EPR spectrum characteristic of the oxidized bacteriochlorophyll dimer and reduced quinone whose intensity was significantly reduced due to the diminished quantum yield of charge separation in the mutant compared to wild type. In the presence of the metal and in the dark, the EPR spectrum measured at the X-band frequency of 9.4 GHz showed a distinctive spin 5/2 Mn(II) signal consisting of 16 lines associated with both allowed and forbidden transitions. Upon illumination, the amplitude of the spectrum is decreased by over 80 % due to oxidation of the metal upon electron transfer to the oxidized bacteriochlorophyll dimer. The EPR spectrum of the Mn-cofactor was also measured at the Q-band frequency of 34 GHz and was better resolved as the signal was composed of the six allowed electronic transitions with only minor contributions from other transitions. A fit of the Q-band EPR spectrum shows that the Mn-cofactor is a high spin Mn(II) species (S = 5/2) that is six-coordinated with an isotropic g-value of 2.0006, a weak zero-field splitting and E/D ratio of approximately 1/3. The ESEEM experiments showed the presence of one (14)N coordinating the Mn-cofactor. The nitrogen atom is assigned to a His by comparing our ESEEM results to those previously reported for Mn(II) ions bound to other proteins and on the basis of the X-ray structure of the M2 mutant that shows the presence of only one His, residue M193, that can coordinate the Mn-cofactor. Together, the data allow the electronic structure and coordination environment of the designed Mn-cofactor in the modified reaction centers to be characterized in detail and compared to those observed in other proteins with Mn-cofactors.

The three-dimensional structures of bacterial reaction centers.

This review presents a broad overview of the research that enabled the structure determination of the bacterial reaction centers from Blastochloris viridis and Rhodobacter sphaeroides, with a focus on the contributions from Duysens, Clayton, and Feher. Early experiments performed in the laboratory of Duysens and others demonstrated the utility of spectroscopic techniques and the presence of photosynthetic complexes in both oxygenic and anoxygenic photosynthesis. The laboratories of Clayton and Feher led efforts to isolate and characterize the bacterial reaction centers. The availability of well-characterized preparations of pure and stable reaction centers allowed the crystallization and subsequent determination of the structures using X-ray diffraction. The three-dimensional structures of reaction centers revealed an overall arrangement of two symmetrical branches of cofactors surrounded by transmembrane helices from the L and M subunits, which also are related by the same twofold symmetry axis. The structure has served as a framework to address several issues concerning bacterial photosynthesis, including the directionality of electron transfer, the properties of the reaction center-cytochrome c 2 complex, and the coupling of proton and electron transfer. Together, these research efforts laid the foundation for ongoing efforts to address an outstanding question in oxygenic photosynthesis, namely the molecular mechanism of water oxidation.

Influence of protein interactions on oxidation/reduction midpoint potentials of cofactors in natural and de novo metalloproteins.

As discussed throughout this special issue, oxidation and reduction reactions play critical roles in the function of many organisms. In photosynthetic organisms, the conversion of light energy drives oxidation and reduction reactions through the transfer of electrons and protons in order to create energy-rich compounds. These reactions occur in proteins such as cytochrome c, a heme-containing water-soluble protein, the bacteriochlorophyll-containing reaction center, and photosystem II where water is oxidized at the manganese cluster. A critical measure describing the ability of cofactors in proteins to participate in such reactions is the oxidation/reduction midpoint potential. In this review, the basic concepts of oxidation/reduction reactions are reviewed with a summary of the experimental approaches used to measure the midpoint potential of metal cofactors. For cofactors in proteins, the midpoint potential not only depends upon the specific chemical characteristics of cofactors but also upon interactions with the surrounding protein, such as the nature of the coordinating ligands and protein environment. These interactions can be tailored to optimize an oxidation/reduction reaction carried out by the protein. As examples, the midpoint potentials of hemes in cytochromes, bacteriochlorophylls in reaction centers, and the manganese cluster of photosystem II are discussed with an emphasis on the influence that protein interactions have on these potentials. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems.

Chemical bonding in copper-based transparent conducting oxides: CuMO2 (M = In, Ga, Sc).

The geometry and electronic structure of copper-based p-type delafossite transparent conducting oxides, CuMO(2) (M = In, Ga, Sc), are studied using the generalized gradient approximation (GGA) corrected for on-site Coulomb interactions (GGA + U). The bonding and valence band compositions of these materials are investigated, and the origins of changes in the valence band features between group 3 and group 13 cations are discussed. Analysis of the effective masses at the valence and conduction band edge explains the experimentally reported conductivity trends.

Light-induced conformational changes in photosynthetic reaction centers: impact of detergents and lipids on the electronic structure of the primary electron donor.

Light-induced hypsochromic shifts of the Q(y) absorption band of the bacteriochlorophyll dimer (P) from 865 to 850 nm were identified using continuous illumination of dark-adapted reaction centers (RCs) from Rhodobacter capsulatus when dispersed in the most commonly used detergent, the zwitterionic lauryl N-dimethylamine-N-oxide. Such a shift is known to be the consequence of the decreased degree of delocalization of P. A 2-fold acceleration of the recovery kinetics of P(+) was found in RCs that underwent light-induced structural changes compared to those where the P-band position did not change. The light-induced shift was irreversible except in the presence of a secondary electron donor. Prolonged (15 min) illumination resulted in a shift in the position of the P-band even in neutral or negatively charged detergents. In contrast, RCs reconstituted into liposomes made from lipids with different headgroup charges showed light-induced shifts only if shorter fatty acid chains were used. The light-induced conformational changes caused a prominent decrease of the redox potential of P ranging from 120 to 160 mV depending on the detergent compared to the potential of P in dark-adapted reaction centers. The measured light-induced potential decreases were 55 to 85 mV larger than those reported for reaction centers where the P-band position remained at 865 nm. The influence of structural factors, such as the delocalization of the electron hole on P(+), the involvement of Tyr M210, and the hydrophobic mismatch between the thickness of the hydrophobic belt of the detergent micelles or the lipid bilayer and the RC protein, on the spectral features and electron transfer kinetics is discussed.

Energetics for oxidation of a bound manganese cofactor in modified bacterial reaction centers.

The energetics of a Mn cofactor bound to modified reaction centers were determined, including the oxidation/reduction midpoint potential and free energy differences for electron transfer. To determine these properties, a series of mutants of Rhodobacter sphaeroides were designed that have a metal-ion binding site that binds Mn2+ with a dissociation constant of 1 µM at pH 9.0 (Thielges et al. (2005) Biochemistry 44, 7389-7394). In addition to the Mn binding site, each mutant had changes near the bacteriochlorophyll dimer, P, that resulted in altered P/P+ oxidation/reduction midpoint potentials, which ranged from 480 mV to above 800 mV compared to 505 mV for wild type. The bound Mn2+ is redox active and after light excitation can rapidly reduce the oxidized primary electron donor, P+. The extent of P+ reduction was found to systematically range from a full reduction in the mutants with high P/P+ midpoint potentials to no reduction in the mutant with a potential comparable to wild type. This dependence of the extent of Mn2+ oxidation on the P/P+ midpoint potential can be understood using an equilibrium model and the Nernst equation, yielding a Mn2+/Mn3+ oxidation/reduction midpoint potential of 625 mV at pH 9. In the presence of bicarbonate, the Mn2+/Mn3+ potential was found to be 90 mV lower with a value of 535 mV suggesting that the bicarbonate serves as a ligand to the bound Mn. Measurement of the electron transfer rates yielded rate constants for Mn2+ oxidation ranging from 30 to 120 s(-1) as the P/P+ midpoint potentials increased from 670 mV to approximately 805 mV in the absence of bicarbonate. In the presence of bicarbonate, the rates increased for each mutant with values ranging from 65 to 165 s(-1), reflecting an increase in the free energy difference due to the lower Mn2+/Mn3+ midpoint potential. This dependence of the rate constant on the P/P+ midpoint potential can be understood using a Marcus relationship that yielded limits of at least 150 s(-1) and 290 meV for the maximal rate constant and reorganization energy, respectively. The implications of these results are discussed in terms of the energetics of proteins with redox active Mn cofactors, in particular, the Mn4Ca cofactor of photosystem II.

The evolutionary pathway from anoxygenic to oxygenic photosynthesis examined by comparison of the properties of photosystem II and bacterial reaction centers.

In photosynthetic organisms, such as purple bacteria, cyanobacteria, and plants, light is captured and converted into energy to create energy-rich compounds. The primary process of energy conversion involves the transfer of electrons from an excited donor molecule to a series of electron acceptors in pigment-protein complexes. Two of these complexes, the bacterial reaction center and photosystem II, are evolutionarily related and structurally similar. However, only photosystem II is capable of performing the unique reaction of water oxidation. An understanding of the evolutionary process that lead to the development of oxygenic photosynthesis can be found by comparison of these two complexes. In this review, we summarize how insight is being gained by examination of the differences in critical functional properties of these complexes and by experimental efforts to alter pigment-protein interactions of the bacterial reaction center in order to enable it to perform reactions, such as amino acid and metal oxidation, observable in photosystem II.

Three-dimensional structures reveal multiple ADP/ATP binding modes for a synthetic class of artificial proteins.

The creation of synthetic enzymes with predefined functions represents a major challenge in future synthetic biology applications. Here, we describe six structures of de novo proteins that have been determined using protein crystallography to address how simple enzymes perform catalysis. Three structures are of a protein, DX, selected for its stability and ability to tightly bind ATP. Despite the addition of ATP to the crystallization conditions, the presence of a bound but distorted ATP was found only under excess ATP conditions, with ADP being present under equimolar conditions or when crystallized for a prolonged period of time. A bound ADP cofactor was evident when Asp was substituted for Val at residue 65, but ATP in a linear configuration is present when Phe was substituted for Tyr at residue 43. These new structures complement previously determined structures of DX and the protein with the Phe 43 to Tyr substitution [Simmons, C. R., et al. (2009) ACS Chem. Biol. 4, 649-658] and together demonstrate the multiple ADP/ATP binding modes from which a model emerges in which the DX protein binds ATP in a configuration that represents a transitional state for the catalysis of ATP to ADP through a slow, metal-free reaction capable of multiple turnovers. This unusual observation suggests that design-free methods can be used to generate novel protein scaffolds that are tailor-made for catalysis.

The influence of hydrogen bonds on the electronic structure of light-harvesting complexes from photosynthetic bacteria.

The influence of hydrogen bonds on the electronic structure of the light-harvesting I complex from Rhodobacter sphaeroides has been examined by site-directed mutagenesis, steady-state optical spectroscopy, and Fourier-transform resonance Raman spectroscopy. Shifts of 4-23 nm in the Q(y) absorption band were observed in seven mutants with single or double changes at Leu alpha44, Trp alpha43, and Trp beta48. Resonance Raman spectra were consistent with the loss of a hydrogen bond with the alteration of either Trp alpha43 or Trp beta48 to Phe. However, when the Trp alpha43 to Phe alteration is combined with Leu alpha44 to Tyr, the spectra show that the loss of the hydrogen bond to alpha43 is compensated by the addition of a new hydrogen bond to Tyr alpha44. Comparison of the absorption and vibrational spectra of the seven mutants suggests that changes in the absorption spectra can be interpreted as being due to both structural and hydrogen-bonding changes. To model these changes, the structural and hydrogen bond changes are considered to be independent of each other. The calculated shifts agree within 1 nm of the observed values. Excellent agreement is also found assuming that the structural changes arise from rotations of the C3-acetyl group conformation and hydrogen bonding. These results provide the basis for a simple model that describes the effect of hydrogen bonds on the electronic structures of the wild-type and mutant light-harvesting I complexes and also is applicable for the light-harvesting II and light-harvesting III complexes. Other possible effects of the mutations, such as changes in the disorder of the environment of the bacteriochlorophylls, are discussed.

Effects of a spaceflight environment on heritable changes in wheat gene expression.

Once it was established that the spaceflight environment was not a drastic impediment to plant growth, a remaining space biology question was whether long-term spaceflight exposure could cause changes in subsequent generations, even if they were returned to a normal Earth environment. In this study, we used a genomic approach to address this question. We tested whether changes in gene expression patterns occur in wheat plants that are several generations removed from growth in space, compared to wheat plants with no spaceflight exposure in their lineage. Wheat flown on Mir for 167 days in 1991 formed viable seeds back on Earth. These seeds were grown on the ground for three additional generations. Gene expression of fourth-generation Mir flight leaves was compared to that of the control leaves by using custom-made wheat microarrays. The data were evaluated using analysis of variance, and transcript abundance of each gene was contrasted among samples with t-tests. After corrections were made for multiple tests, none of the wheat genes represented on the microarrays showed a statistically significant difference in expression between wheat that has spaceflight exposure in their lineage and plants with no spaceflight exposure. This suggests that exposure to the spaceflight environment in low Earth orbit space stations does not cause significant, heritable changes in gene expression patterns in plants.

Structures of proteins and cofactors: X-ray crystallography.

Protein crystallography is the predominately used technique for the determination of the three-dimensional structures of proteins and other macromolecules. In this article, the methodology utilized for the measurement and analysis of the diffraction data from crystals is briefly reviewed. As examples of both the usefulness and difficulties of this technique, the determination of the structures of several photosynthetic pigment-protein complexes is described, namely, the reaction center from purple bacteria, photosystem I and photosystem II from cyanobacteria, the light-harvesting complex II from purple bacteria, and the FMO protein from green bacteria.

EPR, ENDOR, and special TRIPLE measurements of P(*+) in wild type and modified reaction centers from Rb. sphaeroides.

The influence of the protein environment on the primary electron donor, P, a bacteriochlorophyll a dimer, of reaction centers from Rhodobacter sphaeroides, has been investigated using electron paramagnetic resonance and electron nuclear double resonance spectroscopy. These techniques were used to probe the effects on P that are due to alteration of three amino acid residues, His L168, Asn L170, and Asn M199. The introduction of Glu at L168, Asp at L170, or Asp at M199 changes the oxidation/reduction midpoint potential of P in a pH-dependent manner (Williams et al. (2001) Biochemistry 40, 15403-15407). For the double mutant His L168 to Glu and Asn at L170 to Asp, excitation results in electron transfer along the A-side branch of cofactors at pH 7.2, but at pH 9.5, a long-lived state involving B-side cofactors is produced (Haffa et al. (2004) J Phys Chem B 108, 4-7). Using electron paramagnetic resonance spectroscopy, the mutants with alterations of each of the three individual residues and a double mutant, with changes at L168 and L170, were found to have increased linewidths of 10.1-11.0 G compared to the linewidth of 9.6 G for wild type. The Special TRIPLE spectra were pH dependent, and at pH 8, the introduction of aspartate at L170 increased the spin density ratio, rho (L)/rho (M), to 6.1 while an aspartate at the symmetry related position, M199, decreased the ratio to 0.7 compared to the value of 2.1 for wild type. These results indicate that the energy of the two halves of P changes by about 100 meV due to the mutations and are consistent with the interpretation that electrostatic interactions involving these amino acid residues contribute to the switch in pathway of electron transfer.

Bilateral intraparotid and extraparotid Warthin's tumours.

Warthin's tumour is a benign adenoma in the parotid gland, but extraparotid and synchronous bilateral Warthin's tumours may occur. In this report, we describe a patient with simultaneous bilateral involvement of the parotid glands and neck by multiple Warthin's tumours, an occurrence not previously described.

Iron as a bound secondary electron donor in modified bacterial reaction centers.

The binding and oxidation of ferrous iron were studied in wild-type reaction centers and in mutants that have been modified to be both highly oxidizing and able to bind manganese [Thielges et al. (2005) Biochemistry 44, 7389-7394]. After illumination of wild-type reaction centers, steady-state optical spectroscopy showed that the oxidized bacteriochlorophyll dimer, P+, could oxidize iron but only as a second-order reaction at iron concentrations above 100 microM. In the modified reaction centers, P+ was reduced by iron in the presence of sodium bicarbonate with dissociation constants of approximately 1 microM for two mutants with different metal-binding sites. Transient optical spectroscopy showed that P+ was rapidly reduced with first-order rates of 170 and 275 s-1 for the two mutants. The dependence of the amplitude of this rate on the iron concentration yielded a dissociation constant of approximately 1 microM for both mutants, in agreement with the steady-state determination. The oxidation of bound iron by P+ was confirmed by the observation of a light-induced EPR signal centered at g values of 2.2 and 4.3 and attributed to high-spin Fe3+. Bicarbonate was required at pH 7 for low dissociation constants for both iron and manganese binding. The similarity between iron and manganese binding in these mutants provides insight into general properties of metal-binding sites in proteins.

Proton release due to manganese binding and oxidation in modified bacterial reaction centers.

The pH dependence of binding and oxidation of Mn2+ in highly oxidizing reaction centers with designed metal-binding sites was characterized by light-minus-dark optical difference spectroscopy and direct measurements of proton uptake/release. These mutants bind a Mn2+ ion that can efficiently transfer an electron to the oxidized bacteriochlorophyll dimer, as described earlier [Thielges et al. (2005) Biochemistry 44, 7389-7394]. The dissociation constant, KD, significantly increased with decreasing pH. The pH dependence of KD between pH 7 and pH 8 was consistent with the binding of Mn2+ being stabilized by the electrostatic release of two protons. The strong pH dependence of proton release upon Mn2+ binding, with a maximal release of 1.4 H+ per reaction center, was interpreted as being a result of a shift in the pKa values of the coordinating residues and possibly other nearby residues. A small amount of proton release associated with Mn2+ oxidation was observed upon illumination. These results show that functional metal-binding sites can be incorporated into proteins upon consideration of both the metal coordination and protonation states of the ligands.

Crop yield and light/energy efficiency in a closed ecological system: Laboratory Biosphere experiments with wheat and sweet potato.

Two crop growth experiments in the soil-based closed ecological facility, Laboratory Biosphere, were conducted from 2003 to 2004 with candidate space life support crops. Apogee wheat (Utah State University variety) was grown, planted at two densities, 400 and 800 seeds m-2. The lighting regime for the wheat crop was 16 h of light-8 h dark at a total light intensity of around 840 micromoles m-2 s-1 and 48.4 mol m-2 d-1 over 84 days. Average biomass was 1395 g m-2, 16.0 g m-2 d-1 and average seed production was 689 g m-2 and 7.9 g m-2 d-1. The less densely planted side was more productive than the denser planting, with 1634 g m-2 and 18.8 g m-2 d-1 of biomass vs. 1156 g m-2 and 13.3 g m-2 d-1; and a seed harvest of 812.3 g m-2 and 9.3 g m-2 d-1 vs. 566.5 g m-2 and 6.5 g m-2 d-1. Harvest index was 0.49 for the wheat crop. The experiment with sweet potato used TU-82-155 a compact variety developed at Tuskegee University. Light during the sweet potato experiment, on a 18 h on/6 h dark cycle, totaled 5568 total moles of light per square meter in 126 days for the sweet potatoes, or an average of 44.2 mol m-2 d-1. Temperature regime was 28 +/- 3 degrees C day/22 +/- 4 degrees C night. Sweet potato tuber yield was 39.7 kg wet weight, or an average of 7.4 kg m-2, and 7.7 kg dry weight of tubers since dry weight was about 18.6% wet weight. Average per day production was 58.7 g m-2 d-1 wet weight and 11.3 g m-2 d-1. For the wheat, average light efficiency was 0.34 g biomass per mole, and 0.17 g seed per mole. The best area of wheat had an efficiency of light utilization of 0.51 g biomass per mole and 0.22 g seed per mole. For the sweet potato crop, light efficiency per tuber wet weight was 1.33 g mol-1 and 0.34 g dry weight of tuber per mole of light. The best area of tuber production had 1.77 g mol-1 wet weight and 0.34 g mol-1 of light dry weight. The Laboratory Biosphere experiment's light efficiency was somewhat higher than the USU field results but somewhat below greenhouse trials at comparable light levels, and the best portion of the crop at 0.22 g mol-1 was in-between those values. Sweet potato production was overall close to 50% higher than trials using hydroponic methods with TU-82-155 at NASA JSC. Compared to projected yields for the Mars on Earth life support system, these wheat yields were about 15% higher, and the sweet potato yields averaged over 80% higher.