Improved lower urinary tract symptoms after robot-assisted radical prostatectomy: implications for survivorship, treatment selection and patient counselling.

OBJECTIVE: To assess changes in lower urinary tract symptoms (LUTS) and quality of life (QoL) after robot-assisted radical prostatectomy (RARP). PATIENTS AND METHODS: A prospectively curated database of 1917 consecutive RARPs undertaken over an 8-year period from January 2009 to January 2017 was assessed. Preoperative information including age, prostate-specific antigen (PSA) level, body mass index (BMI), International Prostate Symptom Score (IPSS) and QoL score was collected, with IPSS and QoL score compared between baseline (preoperatively) and 12 months post-surgery. RESULTS: Of the 1917 patients who underwent RARP, 1470 with complete data were included in the analysis. Their mean ± sd age, prostate weight and BMI were 62 (±6.7) years, 51 (±17.6) g, and 28 kg/m2 , respectively. Overall, 57% of patients reported an improved IPSS score, whilst 76% reported an IPSS of ≤7 postoperatively. A total of 41% of patients reported an improved QoL and 90.3% of patients with severe preoperative LUTS (IPSS 20-35) demonstrated clinically improved LUTS at 1 year post RARP. The post-RARP mean IPSS in the present study was lower than those reported in the existing post-radiotherapy literature, especially in patients with moderate to severe baseline LUTS (IPSSs ≥ 8). CONCLUSIONS: At 12 months post RARP, most patients reported improved overall LUTS and QoL, with the greatest benefit seen in those patients with a high pre-RARP IPSS. This has implications for treatment selection and preoperative counselling in men being offered active treatment for their prostate cancer. Further analyses of specific IPSS domains and longer follow-up are needed.

Adverse effects of androgen-deprivation therapy in prostate cancer and their management.

OBJECTIVE: To provide an up-to-date summary of current literature on the management of adverse effects of androgen-deprivation therapy (ADT). PATIENTS AND METHODS: All relevant medical literature on men with prostate cancer treated with ADT from 2005 to 2014, and older relevant papers, were reviewed. Recent health advisory statements from the Australian government, societies and advocacy groups have been incorporated to the document. RESULTS: There are numerous adverse effects of ADT that require pro-active prevention and treatment. Ranging from cardiovascular disease, diabetes and osteoporosis, to depression, cognitive decline and sexual dysfunction, the range of adverse effects is wide. Baseline assessment, monitoring, prevention and consultation from a multidisciplinary team are important in minimising the harm from ADT. CONCLUSIONS: This review provides a series of practical recommendations to assist with managing the adverse effects of ADT.

Incisional hernias following robotic-assisted laparoscopic prostatectomy: does the extraction site matter?

The incidence of incisional hernia (IH) following robotic-assisted laparoscopic prostatectomy (RALP) varies widely within the literature (0.4-9.7%). Whilst small hernias may go unnoticed, the potential exists for bowel strangulation and subsequent emergency surgery. We suggest that the extraction site may influence the rate of IH. A retrospective chart review of a single surgeon RALP series was undertaken. One hundred charts were sampled, of which 69 had sufficient data to be analysed. Prior to July 2017, specimen extraction had been via the supra-umbilical port site. After this time, specimens were extracted via a Pfannenstiel incision. Of the 69 patients, 24 underwent RALP prior to July 2017. Three patients developed IH at the supra-umbilical port extended for extraction site in the pre-2017 group and three patients developed IH at the supra-umbilical port (not extraction) site in the post-2017 group. The rate of IH was almost double in the pre-July 2017 group (12.5% vs. 6.7%). No patient developed an incisional hernia at the Pfannenstiel site in the post-2017 group. In our series, no patient developed a hernia at the Pfannenstiel site. This is in keeping with the reported < 1% IH rate following Pfannenstiel specimen extraction. Given that incisional hernias are a known complication of robotic surgery, thought should be given to changing the site of specimen extraction site to lower the rate of incisional hernias and the morbidity associated with such.

Prostate Cancer Survivorship Essentials for men with prostate cancer on androgen deprivation therapy: protocol for a randomised controlled trial of a tele-based nurse-led survivorship care intervention (PCEssentials Hormone Therapy Study).

INTRODUCTION: Androgen deprivation therapy (ADT) is commonly used to treat men with locally advanced or metastatic prostate cancer. Men receiving ADT experience numerous side effects and frequently report unmet supportive care needs. An essential part of quality cancer care is survivorship care. To date, an optimal effective approach to survivorship care for men with prostate cancer on ADT has not been described. This protocol describes a randomised trial of tele-based nurse-led survivorship that addresses this knowledge gap: (1) determine the effectiveness of a nurse-led survivorship care intervention (PCEssentials), relative to usual care, for improving health-related quality of life (HR-QoL) in men with prostate cancer undergoing ADT and (2) evaluate PCEssentials implementation strategies and outcomes, including cost-effectiveness, compared with usual care. METHODS AND ANALYSIS: This is an effectiveness-implementation hybrid (type 1) trial with participants randomised to one of two arms: (1) minimally enhanced usual care and (2) nurse-led prostate cancer survivorship essentials (PCEssentials) delivered over four tele-based sessions, with a booster session 5 months after session 1. Eligible participants are Australian men with prostate cancer commencing ADT and expected to be on ADT for a minimum of 12 months. Participants are followed up at 3, 6 and 12 months postrecruitment. Primary outcomes are HR-QoL and self-efficacy. Secondary outcomes are psychological distress, insomnia, fatigue and physical activity. A concurrent process evaluation with participants and study stakeholders will be undertaken to determine effectiveness of delivery of PCEssentials. ETHICS AND DISSEMINATION: Ethics approval was obtained from the Metro South Health HREC (HREC/2021/QMS/79429). All participants are required to provide written informed consent. Outcomes of this trial will be published in peer-reviewed journals. The findings will be presented at conferences and meetings, local hospital departments, participating organisations/clinical services, and university seminars, and communicated at community and consumer-led forums. TRIAL REGISTRATION NUMBER: ACTRN12622000025730.

Variation in patient reported outcomes following radical prostatectomy: A bi-national registry-based study.

BACKGROUND AND OBJECTIVE: Radical prostatectomy (RP) is a common and widely used treatment for localized prostate cancer. Sequela following RP may include urinary incontinence and sexual dysfunction, outcomes which are recorded within a bi-national Prostate Cancer Outcomes Registry. The objective was to report population-wide urinary incontinence and sexual function outcomes recorded at 12 months following RP; and to quantify and explore factors associated with variation in outcome. MATERIALS AND METHODS: The Prostate Cancer Outcomes Registry of Australia and New Zealand (PCOR-ANZ) was used for this study. Participants were treated with radical prostatectomy between 2016 and 2020. Domain summary scores for urinary incontinence and sexual function from the EPIC-26 instrument were the main outcomes, taken at 12 months following surgery (6-18 months). "Major" urinary and sexual function bother were also assessed. Variation in outcomes was investigated using linear and logistic multivariable regression models adjusted for covariates: age, socioeconomic status, PSA at diagnosis, surgical technique, surgical specimen grade group, margin status, and clinician surgical volume. RESULTS AND CONCLUSIONS: The analytic cohort included 13,083 men with the mean urinary incontinence domain score being 76/100 (SD = 25) with 9.2% reporting major bother. For sexual function, the mean score was 29/100 (SD = 26) with 46% reporting major bother. Of the examined variables, age at surgery and surgical volume category were most predictive of function, with disparities exceeding minimally important differences, though large variation was observed between urologists within volume categories. There is considerable variation in 12-month postprostatectomy functional outcomes. Variation is explained by both patient and clinician factors, though some confounders are unmeasured in this cohort.

Exploring the electron transfer pathways in photosystem I by high-time-resolution electron paramagnetic resonance: observation of the B-side radical pair P700(+)A1B(-) in whole cells of the deuterated green alga Chlamydomonas reinhardtii at cryogenic temperatures.

Crystallographic models of photosystem I (PS I) highlight a symmetrical arrangement of the electron transfer cofactors which are organized in two parallel branches (A, B) relative to a pseudo-C2 symmetry axis that is perpendicular to the membrane plane. Here, we explore the electron transfer pathways of PS I in whole cells of the deuterated green alga Chlamydomonas reinhardtii using high-time-resolution electron paramagnetic resonance (EPR) at cryogenic temperatures. Particular emphasis is given to quantum oscillations detectable in the tertiary radical pairs P700(+)A1A(-) and P700(+)A1B(-) of the electron transfer chain. Results are presented first for the deuterated site-directed mutant PsaA-M684H in which electron transfer beyond the primary electron acceptor A0A on the PsaA branch of electron transfer is impaired. Analysis of the quantum oscillations, observed in a two-dimensional Q-band (34 GHz) EPR experiment, provides the geometry of the B-side radical pair. The orientation of the g tensor of P700(+) in an external reference system is adapted from a time-resolved multifrequency EPR study of deuterated and 15N-substituted cyanobacteria (Link, G.; Berthold, T.; Bechtold, M.; Weidner, J.-U.; Ohmes, E.; Tang, J.; Poluektov, O.; Utschig, L.; Schlesselman, S. L.; Thurnauer, M. C.; Kothe, G. J. Am. Chem. Soc. 2001, 123, 4211-4222). Thus, we obtain the three-dimensional structure of the B-side radical pair following photoexcitation of PS I in its native membrane. The new structure describes the position and orientation of the reduced B-side quinone A1B(-) on a nanosecond time scale after light-induced charge separation. Furthermore, we present results for deuterated wild-type cells of C. reinhardtii demonstrating that both radical pairs P700(+)A1A(-) and P700(+)A1B(-) participate in the electron transfer process according to a mole ratio of 0.71/0.29 in favor of P700(+)A1A(-). A detailed comparison reveals different orientations of A1A(-) and A1B(-) in their respective binding sites such that formation of a strong hydrogen bond from A1(-) to the protein backbone is possible only in the case of A1A(-). We suggest that this is relevant to the rates of forward electron transfer from A1A(-) or A1B(-) to the iron-sulfur center F(X), which differ by a factor of 10. Thus, the present study sheds new light on the orientation of the phylloquinone acceptors in their binding pockets in PS I and the effect this has on function.

Opposing structural changes in two symmetrical polypeptides bring about opposing changes to the thermal stability of a complex integral membrane protein.

The relationship between membrane protein structure and thermal stability has been examined in the reaction centre from the bacterium Rhodobacter sphaeroides, a complex membrane protein comprising three polypeptide chains and 10 cofactors. The core of this protein exhibits an approximate twofold symmetry, the cofactors being held in two membrane-spanning branches by two polypeptides, termed L and M, that have very similar folds. In assays of the thermal stability of wild-type and mutant reaction centres embedded in the native bilayer membrane, replacement of a Phe at position 197 of the M polypeptide by His produced an increase in stability, whereas an opposing replacement of His by Phe at the symmetrical position 168 of the L-polypeptide produced a decrease in stability. In light of the known X-ray crystal structures of wild-type and mutant variants of this protein, and further mutagenesis, it is concluded that these stability changes result from the introduction or removal, respectively, of a hydrogen bond between the side-chain of the His and that of an Asn located two positions along the M or L polypeptide chain, in addition to a hydrogen bond between the His side-chain and an adjacent bacteriochlorophyll cofactor.

A Novel Liver-targeted Testosterone Therapy for Sarcopenia in Androgen Deprived Men With Prostate Cancer.

OBJECTIVE: Androgen deprivation therapy (ADT) reduces muscle and bone mass, increasing frailty in men with prostate cancer. The liver mediates the whole body anabolic effects of testosterone. Based on first-pass metabolism, liver-targeted testosterone treatment (LTTT) entails oral delivery of a small dose of testosterone that does not raise peripheral blood testosterone levels. LTTT reduces blood urea and stimulates protein anabolism in hypogonadal men and postmenopausal women. We investigated whether LTTT prevents loss of lean and bone mass during ADT. METHOD: A 6-month, double-blind, placebo-controlled study of testosterone 40 mg/day in 50 men. Primary outcome measures were lean mass and bone mineral content (BMC). Testosterone, urea and prostate-specific antigen (PSA) were monitored. Patients were withdrawn if PSA exceeded 4 ng/mL. RESULTS: 42 patients completed the study. Mean (95% CI) testosterone rose during LTTT but not placebo treatment [∆ 2.2 (1.3-3.0) vs -0.7 (-1.5 to 0.2) nmol/L; P < 0.01]. Mean PSA level did not change significantly during either treatment. Blood urea fell [∆ -0.4 (-0.9 to -0.1) mmol/L] during LTTT but not placebo [∆ 0.05 (-0.8 to 0.9) mmol/L]. BMC [∆ 49 (5 to 93) g; P < 0.02] and lean mass [∆ 0.8 (-0.1 to 1.7) kg; P = 0.04) increased compared to placebo. Five patients on LTTT withdrew from increased PSA levels, all returning to baseline levels. CONCLUSION: LTTT shows promise as a simple therapy for preventing sarcopenia and bone loss during ADT. LTTT may induce reversible PSA rise in some patients. Further studies are required to optimize LTTT dose in ADT. LTTT has potential application in other catabolic states in men and women.

Compelling EPR evidence that the alternative oxidase is a diiron carboxylate protein.

The alternative oxidase is a respiratory chain protein found in plants, fungi and some parasites that still remains physically uncharacterised. In this report we present EPR evidence from parallel mode experiments which reveal signals at approximately g=16 in both purified alternative oxidase protein (g=16.9), isolated mitochondrial membranes (g=16.1), and in trypanosomal AOX expressed in Escherichia coli membranes (g=16.4). Such signals are indicative of a dicarboxylate diiron centre at the active site of the enzyme. To our knowledge these data represent the first EPR signals from AOX present in its native environment.

Reaction centres: the structure and evolution of biological solar power.

Reaction centres are complexes of pigment and protein that convert the electromagnetic energy of sunlight into chemical potential energy. They are found in plants, algae and a variety of bacterial species, and vary greatly in their composition and complexity. New structural information has highlighted features that are common to the different types of reaction centre and has provided insights into some of the key differences between reaction centres from different sources. New ideas have also emerged on how contemporary reaction centres might have evolved and on the possible origin of the first chlorophyll-protein complexes to harness the power of sunlight.

Development of Indicators to Assess Quality of Care for Prostate Cancer.

BACKGROUND: The development, monitoring, and reporting of indicator measures that describe standard of care provide the gold standard for assessing quality of care and patient outcomes. Although indicator measures have been reported, little evidence of their use in measuring and benchmarking performance is available. A standard set, defining numerator, denominator, and risk adjustments, will enable global benchmarking of quality of care. OBJECTIVE: To develop a set of indicators to enable assessment and reporting of quality of care for men with localised prostate cancer (PCa). DESIGN, SETTING, AND PARTICIPANTS: Candidate indicators were identified from the literature. An international panel was invited to participate in a modified Delphi process. Teleconferences were held before and after each voting round to provide instruction and to review results. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Panellists were asked to rate each proposed indicator on a Likert scale of 1-9 in a two-round iterative process. Calculations required to report on the endorsed indicators were evaluated and modified to reflect the data capture of the Prostate Cancer Outcomes Registry-Australia and New Zealand (PCOR-ANZ). RESULTS AND LIMITATIONS: A total of 97 candidate indicators were identified, of which 12 were endorsed. The set includes indicators covering pre-, intra-, and post-treatment of PCa care, within the limits of the data captured by PCOR-ANZ. CONCLUSIONS: The 12 endorsed quality measures enable international benchmarking on the quality of care of men with localised PCa. Reporting on these indicators enhances safety and efficacy of treatment, reduces variation in care, and can improve patient outcomes. PATIENT SUMMARY: PCa has the highest incidence of all cancers in men. Early diagnosis and relatively high survival rates mean issues of quality of care and best possible health outcomes for patients are important. This paper identifies 12 important measurable quality indicators in PCa care.

Bidirectional electron transfer in photosystem I: replacement of the symmetry-breaking tryptophan close to the PsaB-bound phylloquinone A1B with a glycine residue alters the redox properties of A1B and blocks forward electron transfer at cryogenic temperatures.

A conserved tryptophan residue located between the A(1B) and F(X) redox centres on the PsaB side of the Photosystem I reaction centre has been mutated to a glycine in Chlamydomonas reinhardtii, thereby matching the conserved residue found in the equivalent position on the PsaA side. This mutant (PsaB:W669G) was studied using EPR spectroscopy with a view to understanding the molecular basis of the reported kinetic differences in forward electron transfer from the A(1A) and the A(1B) phyllo(semi)quinones. The kinetics of A(1)(-) reoxidation due to forward electron transfer or charge recombination were measured by electron spin echo spectroscopy at 265 K and 100 K, respectively. At 265 K, the reoxidation kinetics are considerably lengthened in the mutant in comparison to the wild-type. Under conditions in which F(X) is initially oxidised the kinetics of charge recombination at 100 K are found to be biphasic in the mutant while they are substantially monophasic in the wild-type. Pre-reduction of F(X) leads to biphasic kinetics in the wild-type, but does not alter the already biphasic kinetic properties of the PsaB:W669G mutant. Reduction of the [4Fe-4S] clusters F(A) and F(B) by illumination at 15 K is suppressed in the mutant. The results provide further support for the bi-directional model of electron transfer in Photosystem I of C. reinhardtii, and indicate that the replacement of the tryptophan residue with glycine mainly affects the redox properties of the PsaB bound phylloquinone A(1B).

Assignment of a kinetic component to electron transfer between iron-sulfur clusters F(X) and F(A/B) of Photosystem I.

We studied the kinetics of reoxidation of the phylloquinones in Chlamydomonas reinhardtii Photosystem I using site-directed mutations in the PhQ(A)-binding site and of the residues serving as the axial ligand to ec3(A) and ec3(B) chlorophylls. In wild type PS I, these kinetics are biphasic, and mutations in the binding region of PhQ(A) induced a specific slowing down of the slow component. This slowing allowed detection of a previously unobserved 180-ns phase having spectral characteristics that differ from electron transfer between phylloquinones and F(X). The new kinetic phase thus reflects a different reaction that we ascribe to oxidation of F(X)(-) by the F(A/B) FeS clusters. These absorption changes partly account for the differences between the spectra associated with the two kinetic components assigned to phylloquinone reoxidation. In the mutant in which the axial ligand to ec3(A) (PsaA-Met688) was targeted, about 25% of charge separations ended in P(700)(+)A(0)(-) charge recombination; no such recombination was detected in the B-side symmetric mutant. Despite significant changes in the amplitude of the components ascribed to phylloquinone reoxidation in the two mutants, the overall nanosecond absorption changes were similar to the wild type. This suggests that these absorption changes are similar for the two different phylloquinones and that part of the differences between the decay-associated spectra of the two components reflect a contribution from different electron acceptors, i.e. from an inter-FeS cluster electron transfer.

Proteins, chlorophylls and lipids: X-ray analysis of a three-way relationship.

Photosynthetic reaction centres and light harvesting complexes have been at the forefront of crystallographic studies of integral membrane proteins. In recent years, there have been spectacular advances in our understanding of the structure of (bacterio)chlorophyll-containing membrane proteins from oxygenic and anoxygenic phototrophs. In these complex structures, the protein scaffold encases different combinations of cofactors and interacts with several tightly bound lipid species that play a variety of hitherto unrecognized structural roles. Some of these lipids have relevance to the physiological function of the protein, whereas others are important for the formation of highly ordered crystals. The first site-directed mutagenesis studies of individual lipid binding sites have now underlined the importance of the lipid component for the structural stability of protein-cofactor-lipid complexes.

Modelling of the electron transfer reactions in Photosystem I by electron tunnelling theory: the phylloquinones bound to the PsaA and the PsaB reaction centre subunits of PS I are almost isoenergetic to the iron-sulfur cluster F(X).

Photosystem I is a large macromolecular complex located in the thylakoid membranes of chloroplasts and in cyanobacteria that catalyses the light driven reduction of ferredoxin and oxidation of plastocyanin. Due to the very negative redox potential of the primary electron transfer cofactors accepting electrons, direct estimation by redox titration of the energetics of the system is hampered. However, the rates of electron transfer reactions are related to the thermodynamic properties of the system. Hence, several spectroscopic and biochemical techniques have been employed, in combination with the classical Marcus theory for electron transfer tunnelling, in order to access these parameters. Nevertheless, the values which have been presented are very variable. In particular, for the case of the tightly bound phylloquinone molecule A(1), the values of the redox potentials reported in the literature vary over a range of about 350 mV. Previous models of Photosystem I have assumed a unidirectional electron transfer model. In the present study, experimental evidence obtained by means of time resolved absorption, photovoltage, and electron paramagnetic resonance measurements are reviewed and analysed in terms of a bi-directional kinetic model for electron transfer reactions. This model takes into consideration the thermodynamic equilibrium between the iron-sulfur centre F(X) and the phylloquinone bound to either the PsaA (A(1A)) or the PsaB (A(1B)) subunit of the reaction centre and the equilibrium between the iron-sulfur centres F(A) and F(B). The experimentally determined decay lifetimes in the range of sub-picosecond to the microsecond time domains can be satisfactorily simulated, taking into consideration the edge-to-edge distances between redox cofactors and driving forces reported in the literature. The only exception to this general behaviour is the case of phylloquinone (A(1)) reoxidation. In order to describe the reported rates of the biphasic decay, of about 20 and 200 ns, associated with this electron transfer step, the redox potentials of the quinones are estimated to be almost isoenergetic with that of the iron sulfur centre F(X). A driving force in the range of 5 to 15 meV is estimated for these reactions, being slightly exergonic in the case of the A(1B) quinone and slightly endergonic, in the case of the A(1A) quinone. The simulation presented in this analysis not only describes the kinetic data obtained for the wild type samples at room temperature and is consistent with estimates of activation energy by the analysis of temperature dependence, but can also explain the effect of the mutations around the PsaB quinone binding pocket. A model of the overall energetics of the system is derived, which suggests that the only substantially irreversible electron transfer reactions are the reoxidation of A(0) on both electron transfer branches and the reduction of F(A) by F(X).

Radicals associated with the catalytic intermediates of bovine cytochrome c oxidase.

Two radicals have been detected previously by electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) spectroscopies in bovine cytochrome oxidase after reaction with hydrogen peroxide, but no correlation could be made with predicted levels of optically detectable intermediates (P(M), F and F(z.rad;)) that are formed. This work has been extended by optical quantitation of intermediates in the EPR/ENDOR sample tubes, and by comparison with an analysis of intermediates formed by reaction with carbon monoxide in the presence of oxygen. The narrow radical, attributed previously to a porphyrin cation, is detectable at low levels even in untreated oxidase and increases with hydrogen peroxide treatments generally. It is presumed to arise from a side-reaction unrelated to the catalytic intermediates. The broad radical, attributed previously to a tryptophan radical, is observed only in samples with a significant level of F(z.rad;) but when F(z.rad;) is generated with hydrogen peroxide, is always accompanied by the narrow radical. When P(M) is produced at high pH with CO/O(2), no EPR-detectable radicals are formed. Conversion of the CO/O(2)-generated P(M) into F(z.rad;) when pH is lowered is accompanied by the appearance of a broad radical whose ENDOR spectrum corresponds to a tryptophan cation. Quantitation of its EPR intensity indicates that it is around 3% of the level of F(z.rad;) determined optically. It is concluded that low pH causes a change of protonation pattern in P(M) which induces partial electron redistribution and tryptophan cation radical formation in F(z.rad;). These protonation changes may mimic a key step of the proton translocation process.

Bidirectional electron transfer in photosystem I: electron transfer on the PsaA side is not essential for phototrophic growth in Chlamydomonas.

We have used pulsed electron paramagnetic resonance (EPR) measurements of the electron spin polarised (ESP) signals arising from the geminate radical pair P700(z.rad;+)/A(1)(z.rad;-) to detect electron transfer on both the PsaA and PsaB branches of redox cofactors in the photosystem I (PSI) reaction centre of Chlamydomonas reinhardtii. We have also used electron nuclear double resonance (ENDOR) spectroscopy to monitor the electronic structure of the bound phyllosemiquinones on both the PsaA and PsaB polypeptides. Both these spectroscopic assays have been used to analyse the effects of site-directed mutations to the axial ligands of the primary chlorophyll electron acceptor(s) A(0) and the conserved tryptophan in the PsaB phylloquinone (A(1)) binding pocket. Substitution of histidine for the axial ligand methionine on the PsaA branch (PsaA-M684H) blocks electron transfer to the PsaA-branch phylloquinone, and blocks photoaccumulation of the PsaA-branch phyllosemiquinone. However, this does not prevent photoautotrophic growth, indicating that electron transfer via the PsaB branch must take place and is alone sufficient to support growth. The corresponding substitution on the PsaB branch (PsaB-M664H) blocks kinetic electron transfer to the PsaB phylloquinone at 100 K, but does not block the photoaccumulation of the phyllosemiquinone. This transformant is unable to grow photoautotrophically although PsaA-branch electron transfer to and from the phyllosemiquinone is functional, indicating that the B branch of electron transfer may be essential for photoautotrophic growth. Mutation of the conserved tryptophan PsaB-W673 to leucine affects the electronic structure of the PsaB phyllosemiquinone, and also prevents photoautotrophic growth.