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PubMed1980

Light intensity saturation properties of O2 yields in a sequence of flashes in Chlorella.

As a function of the light intensity of flash n in a sequence, the O2 yields Yn, Yn+1 and Yn+2 have been measured: n = 1, 2, 3 and 6 in the examples given. It is shown that: (1) No double hit exists in the first saturating flash in Chlorella. (2) the flash saturation curve of the O2 yield Yn+1 as a function of the intensity of flash n exhibits a small sigmoidal shape at weak light. (3) If Yn+1 is detected at different times after the flash n of variable intensity, a well developed lag distinguishes the saturation curve of the O2 yield measured a long time after flash n (200 ms) with respect to that measured at shorter time (300 microseconds). Nevertheless, a large amount of double hits with the transitions S1 leads to S3 cannot occur in each flash, because it would lead to a periodicity of three rather than four in the O2 yield pattern. The saturation curve of the transition S2* leads to S3 is different from the other S-state saturation curves which are close to an exponential function; even with a short flash (0.3 microseconds), this curve shows a small lag at low light intensity, and its saturation intensity is higher than that of the other transitions. The low quantum yield of the transition S2* leads to S3 at low flash light intensity is explained by a product, T, partially inhibiting the formation of S3; at higher intensity, the quantity of formed S2* being larger than that of available T, only a part of S2* is inhibited and the quantum yield is higher than at low intensity.

Chlorella↗
PubMed1992

Singlet oxygen production and fluorescence yields of merocyanine 540: a comparative study in solution and model membrane systems.

Singlet oxygen and fluorescence quantum yields of merocyanine 540 were measured in solution (methanol, ethanol, n-heptanol) and in model membrane systems (cationic micelles, unilamellar dimyristoyl- and dipalmitoylphosphatidylcholine vesicles). Both singlet oxygen quantum yields and fluorescence quantum yields increase with increasing viscosity/rigidity of the surrounding medium: the yield of singlet oxygen production (24 degrees C) goes from 0.002 in methanol to 0.04 in dipalmitoylphosphatidylcholine vesicles, and fluorescence yields (25 degrees C) change from 0.14 to 0.61 in the same media. The data are consistent with previous findings that photoisomerization is in direct competition with intersystem crossing and radiative relaxation. Therefore, a singlet oxygen yield close to the maximum value of 0.11 can only be achieved after both photoisomerization and internal conversion are prevented by a highly viscous environment.

Cell Membrane↗
PubMed1985

Cardiovascular and other diseases in smokers of low yield cigarettes.

The association of smoking low yield cigarettes with the risk of cancer, cardiovascular disease, and other disease associated previously with smoking is controversial. In 1979 we began a prospective epidemiologic study of this subject. We here report on the first 4 years of follow-up in the 16,270 current, regular cigarette smokers and the 42,113 subjects who never used any form of tobacco enrolled in the study. In multivariate analyses that included age, sex, race, number of cigarettes smoked per day and other factors related to cardiovascular disease, the risk of cardiovascular diseases was consistently higher in smokers of higher than in smokers of lower yield cigarettes, although the magnitude of the difference in risk was very small. The risks of cancer of the trachea, bronchus and lung, of all smoking-related cancers as a group, of diseases of the respiratory system, and of peptic ulcer diseases were not significantly associated with yield in smokers. The incidence rates of cardiovascular diseases considered as a group, cancer of the trachea, bronchus, and lung and all smoking-related cancers were higher in smokers of low yield cigarettes than in never users of any form of tobacco. We conclude that the smoking of low yield cigarettes is not without associated hazard. On the other hand, the results suggest that smokers who cannot quit might best use the least number of the lowest yield cigarette.

Adult↗
PubMed1989

Evaluation of the yield stress of normal blood as a function of fibrinogen concentration and hematocrit.

The yield stress is a sensitive index of blood fluidity at low shear. Seven healthy adults were studied at hematocrits varying between 40 and 80% and fibrinogen concentrations from 0.0 to 0.935 g/dl. Multivariable analysis was used to determine the functional dependence of yield stress on hematocrit and fibrinogen level. The major findings from this analysis include a decreasing effect of fibrinogen at high concentrations (saturation effect), a relative insensitivity of yield stress to fibrinogen at low concentration (threshold effect), and a strong interaction between the effects of hematocrit and fibrinogen concentration on yield stress. Our results give the normal range of yield stress for a given value of fibrinogen and hematocrit and can be used to predict the effect of reductions in hematocrit or fibrinogen on the yield stress of normal blood.

Adult↗
PubMed1976

Translocation yield from the mouse spermatogonial stem cell following fractionated X-ray treatments: influence of unequal fraction size and of increasing fractionation interval.

(1) The genetic response of the mouse spermatogonial stem cell to a high dose of X-rays given in two unequal fractions 24 h apart can be dependent upon the order in which the two fractions are given. When 1000 R was administered as 100 R followed by 900 R the recovered translocation yield (22%) was similar to that which can be obtained by extrapolation from lower doses and also to that of a 500 + 500 R 24 h fractionation. By contrast, when the 900 R preceded the 100 R the response was much lower (7.4%), yet still greater than that produced by a single 1000 R treatment (4.5%). The same order of effectiveness was observed for length of sterile period. (2) The sub-additive translocation yields previously obtained with 800 R treatments given in fractions of 500 R and 300 R at intervals of 3-12 days were found to be maintained with intervals up to at least 15 days but additivity was regained by the end of the third week. Sterile period data indicated that with these intervals the germinal epithelium had recovered sufficiently from the first fraction for spermatogenesis to restart before the second fraction was given. (3) It is concluded from the two experiments that (a) 24 h after a radiation exposure the surviving stem cells are more sensitive than formerly both to killing and genetic damage, (b) at this time they are no longer heterogeneous in their radiosensitivities, so that increasing yields of genetic damage may be obtained with increasing dose i.e. there is no fall in yield at higher doses, (c) the change in sensitivity could be a consequence of a synchronization to a sensitive stage in a cell cycle, or to a transitional phase preparatory to entering a different cell cycle. (d) to achieve rapid repopulation of the germinal epithelium the surviving stem cells are stimulated to enter a shorter cell cycle and this is the cause of the sub-additive translocation yields with fractionation intervals of 3-15 days, (e) the recommencement of spermatogenesis is associated with the reestablishment of the heterogeneity in radiosensitivity among the stem cells. At this time additive translocation yields can again be recovered.

Animals↗
PubMed1995

Smokers' behaviour and exposure according to cigarette yield and smoking experience.

The influence of cigarette yield and length of smoking experience on smoking behaviour and biomarker levels was sought in 108 smokers who have never changed cigarette class. Smoking parameters carboxyhaemoglobin percentage (COHb), urinary nicotine, and its metabolites, mutagens, and thioethers were measured. Cigarette yield does not affect daily consumption or smoke volume puffed per cigarette. But the inhalation depth increases with decreasing cigarette yield and with length of smoking habit. The COHb level after the first cigarette in the morning increases significantly with CO cigarette yield and length of smoking experience. In the evening, only the cigarette yield has an effect on COHb level. Biomarker levels excreted in urine are generally lower for females than for males. They tend to increase with smoking history. Only COHb level and total urinary nicotine metabolites (Barlow index) are weakly correlated with cigarette yield. The absence of significant differences due to cigarette class in urinary biomarkers can be explained by changes in inhalation depth, individual differences of metabolism, and limited specificity of some markers (mutagens, thioethers).

Adult↗
PubMed1983

A comparison of the yields of tar, nicotine, and carbon monoxide of 36 brands of Canadian cigarettes tested under three conditions.

A number of countries, including Canada, sponsor routine monitoring of cigarette tar, nicotine, and carbon monoxide yields which are evaluated by cigarette-smoking machines according to a standard protocol. These standardized yields continue to decline as tobacco companies modify their brands to meet consumers' demand for "light" products. This trend toward cigarettes with low average deliveries of toxic substances may reduce health risks for some people. However, switching to low-yield cigarettes may not result in reduced risks for smokers who smoke these cigarettes intensively. Thirty-six brands of Canadian cigarettes, including 28 with ventilated filters, were tested under standard conditions and 2 others in order to determine how yields of tar, nicotine, and carbon monoxide change when cigarettes are manipulated by smokers in order to increase their smoke intake. While the rank order yields of tar, nicotine, and carbon monoxide was preserved, the average yields of all three substances more than doubled when cigarettes were intensively smoked in comparison with standard smoking.

Carbon Monoxide↗
PubMed1985

Respiratory morbidity in smokers of low- and high-yield cigarettes.

To study the association between smoking cigarettes with a low yield of tar and nicotine (tar less than 15.0 mg per cigarette and nicotine less than 1.0 mg) and respiratory disease, we reviewed the medical records of 4,610 current, regular cigarette smokers and 2,035 persons who had never used any form of tobacco and who were enrolled in a smoking study. In the year after recruitment to the study, the percentage of subjects with pneumonia or influenza was lower in female but not in male smokers of low-yield cigarettes. The percentage of subjects with any disease of the respiratory tract was lower in both male and female smokers of low-yield cigarettes. In multiple logistic regression analyses in which tar was included as a continuous variable and in which we also controlled for age, sex, race, and number of cigarettes smoked per day, smoking lower tar cigarettes was associated with lower risk for pneumonia or influenza, but not with the risk for other acute respiratory infections, other diseases of the upper respiratory tract, chronic obstructive pulmonary disease and allied conditions, or all respiratory diseases considered as a group. In other multiple logistic regression analyses, in which we controlled for age, race, and sex, smokers of low-yield cigarettes had a higher risk for pneumonia or influenza and chronic obstructive pulmonary disease when compared with subjects who had never used tobacco. We conclude that, with regard to pneumonia and influenza seen in an outpatient setting, smoking low-yield cigarettes is probably less hazardous than smoking high-yield cigarettes, but it still represents a considerable hazard compared with not smoking cigarettes at all.

Female↗
PubMed1992

An enhancement of the yield of X-ray-induced Minute mutations in the c3G female-ywmf-2 male system of Drosophila melanogaster.

The possible enhancement of the yield of X-ray-induced Minute mutations in the c3G female-ywmf-2 male system which is proposed to be responsible for the high production of spontaneous Minute mutations was investigated. To determine and compare the yield of X-ray-induced Minute mutations exactly, four series of crosses were made: (a) ywmf-2 male x Oregon-R (OrR) female crosses, spontaneous Minute mutations were scored; (b) ywmf-2 male x c3G female crosses, spontaneous Minute mutations produced in the c3G female-ywmf-2 male system were evaluated; (c) X-irradiated ywmf-2 male x OrR female crosses, the yield of Minutes induced by X-rays in the different stages of male germ cells was evaluated; and (d) X-irradiated ywmf-2 male x c3G female crosses, the yield of X-ray-induced Minutes in the c3G female-ywmf-2 male system was evaluated. The results show that the yield of X-ray-induced Minutes recorded in the c3G female-ywmf-2 male system is 2.37-16.55 times more than that in the ywmf-2 male x OrR female crosses. This finding clearly indicates that the yield of these mutations is greatly enhanced in the c3G female-ywmf-2 male system. This possibly suggests that the c3G female-ywmf-2 male system may be responsible not only for the high production of spontaneous Minute mutations but also for the high formation of radiation-induced Minutes.

Animals↗
PubMed1991

Yield and grain quality of spring wheat (Triticum aestivum L., cv. Drabant) exposed to different concentrations of ozone in open-top chambers.

Spring wheat (Triticum aestivum L., cv. Drabant) was exposed to different concentrations of ozone in open-top chambers for two growing seasons, 1987 and 1988, at a site located in south-west Sweden. The chambers were placed in a field of commercially grown spring wheat. The treatments were charcoal-filtered air (CF), non-filtered air (NF) and non-filtered air plus extra ozone (NF(+)). In 1988, one additional ozone concentration (NF(++)) was used. Grain yield was affected by the ozone concentration of the air. Air filtration resulted in an increase in grain yield of about 7% in both years, compared to NF. The addition of ozone (NF(+), NF(++)) reduced grain yield and increased the content of crude protein of the grain in both years. Filtration of the air had no significant effect on the content of crude protein, compared to NF. The results showed a strong positive chamber effect on grain yield in the cold and wet summer of 1987. In 1988, there was no net chamber effect on grain yield. The relative differences between the CF, NF and NF(+) treatments with respect to grain yield were of the same magnitude in the two years, despite the very different weather conditions.

Journal Article↗
PubMed2004

Determination of quantum yields for the photolysis of Fe(III)-hydroxo complexes in aqueous solution using a novel kinetic method.

The determination of quantum yields for the photolysis of Fe(III)-hydroxo complexes is important for the quantitative investigation of hydroxyl radical (*OH) production, not only in a natural water body, but also in the photo-Fenton process. A novel kinetic method, using a *OH probe compound, was established for the determination of the quantum yields in this study. The method was based on measuring the pseudo-first-order rate constant of the photodecomposition of dimethylsulfoxide (DMSO) in which DMSO and its primary products scavenged the *OH at an identical rate. The preliminary experiments for the photodecomposition kinetics supported the suitability of DMSOs as a probe compound for determining quantum yields. The individual quantum yields for the photolysis of the monomeric Fe(III) complexes, in the wavelength range 240-380 nm, were determined by the photodecomposition kinetics of the hydroxyl radical (*OH) probe compound (DMSO). The determined values of the individual quantum yields were 0.046+/-0.00052 for Fe3+ (H2O)6 (hexaaquo ion) and 0.69+/-0.025 for Fe(OH)2+ (H2O)5 (hydroxypentaaquo ion) at 254 nm, and showed decreasing values with increasing wavelength, in the ranges of 240-380 nm. The quantum yields between 240 and 280 nm were newly reported in this study, and the values obtained between 280 and 380 nm were in good agreement with the literature values.

Dimethyl Sulfoxide↗
PubMed2005

Influence of the protein oligomericity on final yield after affinity tag removal in purification of recombinant proteins.

The new aspect concerning the applicability of histidine and other affinity tags for the purification of oligomeric proteins, with particular emphasis on cleavage efficiency and final yield, is presented in this study. The final yield depends on both the cleavage efficiency and the degree of oligomerization of the protein. Cleavage procedures that are good enough for monomeric proteins can be problematic for oligomeric proteins. Random distribution of uncleaved or partially cleaved affinity tags among oligomers is the main cause of reduced yields. A trimeric protein, tumour necrosis factor alpha (TNF-alpha), bearing different histidine tags, was used as a model protein to explore and confirm this theoretical concept. Analysis of mixed TNF trimers, prepared from tag-free TNF doped with various amounts of histidine-tagged TNF, revealed an increased retention of the trimeric protein on immobilized metal-ion affinity chromatography (IMAC) columns. When 20% of histidine-tagged TNF was added, more than 50% of the protein was retained on the IMAC column. Thus, the applicability of histidine- and other affinity tags for purifying oligomeric proteins is significantly prejudiced in the case of higher oligomers. Various histidine-tags were fused to the N-terminus of full-length TNF-alpha and to the truncated form (dN6) of TNF-alpha. Two-step IMAC separation was used for purification. In the first step, IMAC-1, over 95% purity of histidine-tagged protein was achieved in all cases. Endo- and exoproteolytic removal of histidine tags with enterokinase (EKmax) and aminodipeptidase (DAPase) was studied and the major parameters affecting cleavage efficiency, microheterogeneity and final yield are critically discussed. IMAC-2 was used as the second and final step for removing the cleavage enzyme, cleaved tags, unprocessed protein and some other impurities. Selection of the optimal cleavage enzyme depends on the amino acid composition of the N-terminus and the intended use of the purified protein. The main conclusion is that special caution should be taken when introducing affinity tags to oligomeric proteins, with the final goal to produce pure, tag-free protein with acceptable yields. Given the same enzyme cleavage efficiency one can expect progressively reduced final protein yields with increasing degree of oligomerization. This should be considered as a general rule.

Affinity Labels↗
PubMed2005

Yield enhancement genes: seeds for growth.

Yield is a multifactorial trait, integrating various developmental and physiological processes. Despite this complexity, evidence is mounting that yield can be increased by the genetic modification of single genes. Positive results have been obtained by targeting different yield constituents, indicating that there is ample room for further yield improvement by genetic means. Successful targets include photosynthesis, starch biosynthesis, plant architecture and transcriptional networks controlling plant development. Most of the current data have been obtained in a (semi-)controlled environment and relate to yield calculated on a per plant basis. Demonstrating the ability to transfer these effects to field-grown plants and with reference to yield on a per area unit basis will be a crucial step in establishing the agronomic importance of these findings.

Arabidopsis↗
PubMed2006

Yield of tissue sampling for subepithelial lesions evaluated by EUS: a comparison between forceps biopsies and endoscopic submucosal resection.

BACKGROUND: In most circumstances, subepithelial tumors lack distinct endoscopic and ultrasonographic features. Consequently, definitive diagnosis usually requires tissue acquisition and pathologic confirmation. Establishing a tissue diagnosis is difficult because the yield of forceps biopsies is low. However, prospective data evaluating tissue sampling techniques for subepithelial lesions are currently lacking. OBJECTIVE: Our purpose was to prospectively determine the diagnostic yield of endoscopic submucosal-mucosal resection (ESMR) compared with forceps biopsy for lesions limited to the submucosa (third endosonographic layer) of the GI tract. DESIGN: A prospective head-to-head comparison was performed. SETTING: The study was performed in a tertiary care hospital. PATIENTS: Study patients were 23 adults with subepithelial lesions limited to the submucosa. INTERVENTION: All submucosal lesions underwent forceps biopsy followed by endoscopic submucosal resection. Biopsy specimens were obtained with large-capacity "jumbo" forceps. A total of 4 double passes (8 biopsy specimens) were collected from each lesion with use of the bite-on-bite technique. Endoscopic resection was then performed with an electrosurgical snare or cap-fitted endoscopic mucosal resection device. MAIN OUTCOME MEASUREMENT: The main outcome measurement was the diagnostic yield of biopsy forceps compared with endoscopic submucosal resection. RESULTS: Twenty-three patients with lesions limited to the submucosa were identified by endoscopic ultrasonography. All lesions underwent forceps biopsy followed by ESMR. The diagnostic yield of the jumbo forceps biopsy was 4 of 23 (17%), whereas the diagnostic yield of ESMR was 20 of 23 (87%) (P = .0001, McNemar test). CONCLUSION: In the evaluation of subepithelial lesions limited to the submucosa, ESMR has a significantly higher diagnostic yield than jumbo forceps biopsy with use of the bite-on-bite technique.

Adult↗
PubMed2026

Molecular diagnostic yield and barriers in inherited retinal diseases: a retrospective cohort study.

OBJECTIVE: To evaluate the diagnostic yield of panel-based genetic testing for inherited retinal diseases (IRDs) and identify barriers to molecular resolution. DESIGN: Retrospective cohort. PARTICIPANTS: A total of 404 patients with clinically confirmed IRDs who were evaluated at the Adult Inherited Retinal Dystrophy Service, Ontario, Canada (October 2021-September 2024). METHODS: Patients underwent targeted massive parallel sequencing panel testing. Diagnostic yield was calculated, and unresolved cases were reviewed. Associations between yield, phenotype, ethnicity, and sex were assessed using χ² analysis. RESULTS: Of 685 referrals, 570 had confirmed IRDs. After we excluded 140 pending results and 26 patients who declined testing, 404 patients were analyzed. At referral, 94 patients (23.2%) had a previous molecular diagnosis, and 138 (34.0%) were diagnosed through clinic-initiated testing, giving an overall yield of 57.4%. Yield varied significantly by phenotype (χ², P = 1.4 × 10⁻⁶), from 94.4% in vitelliform macular dystrophies to 25.0% in vitreoretinopathies, with no sex association (P = 1.0). Disease-causing variants were identified in 83 IRD-associated genes, most frequently ABCA4, USH2A, and BEST1. Of 172 unresolved cases, 62 (36.0%) had negative panels, and 110 (63.9%) were inconclusive, including 30 with unphased pathogenic variants in recessive genes and 10 with high-suspicion variants of uncertain significance. Key barriers included limited family availability for phasing, restricted access to functional assays, and lack of public coverage for whole-exome or whole-genome sequencing. CONCLUSIONS: Massive parallel sequencing-based panel testing achieved a 57% diagnostic yield in this IRD population. Success was strongly phenotype-dependent with substantial heterogeneity. Whole-exome sequencing, whole-genome sequencing, family segregation, and functional genomics could improve diagnostic outcomes and management.

Humans↗
PubMed2026

Genetic legacy effects in a mungbean-wheat rotation reveal potential to breed for system-level yield gains.

Legume crops provide protein-rich food, serve as critical disease breaks in cereal rotations, and contribute to soil fertility through symbiotic nitrogen fixation. However, crop improvement programs typically focus on within-crop performance rather than system-level benefits. We hypothesize that legacy effects (the influence of one crop's genotype on subsequent crop performance) are under genetic control and could be targeted in breeding programs. To test this, we evaluated how 309 genetically diverse mungbean genotypes influenced subsequent wheat performance. The mungbean panel was grown, followed by a single wheat cultivar sown in the same plots. Remarkably, wheat yield varied by nearly 1 t ha-1 (2.52-3.49 t ha-1), depending solely on the preceding mungbean genotype. Legacy effects showed moderate heritability (H2: 0.43-0.65), suggesting untapped genetic potential for breeding. However, these estimates were derived from a single site and season and require validation across environments. Analyses of mungbean traits, soil properties, and volatile organic compounds identified root architecture, symbiotic nitrogen fixation, and the soil microbiome as potential contributors to legacy effects, although these mechanisms remain to be tested directly. Haplotype mapping identified genomic regions in mungbean associated with wheat yield and, to a lesser extent, grain protein, revealing trade-offs between within-crop performance and legacy effects. Genetic simulations based on empirically derived marker effects compared genomic selection strategies targeting mungbean yield, wheat yield, or both simultaneously. A selection strategy placing equal weight on mungbean yield and subsequent wheat yield (50:50 weighting) achieved simultaneous gains in both crops (19.5% and 7.6%), highlighting the potential to breed for system-level productivity with reduced input requirements.

crop rotations↗
PubMed2005

Novel pathway engineering design of the anaerobic central metabolic pathway in Escherichia coli to increase succinate yield and productivity.

A novel in vivo method of producing succinate has been developed. A genetically engineered Escherichia coli strain has been constructed to meet the NADH requirement and carbon demand to produce high quantities and yield of succinate by strategically implementing metabolic pathway alterations. Currently, the maximum theoretical succinate yield under strictly anaerobic conditions through the fermentative succinate biosynthesis pathway is limited to one mole per mole of glucose due to NADH limitation. The implemented strategic design involves the construction of a dual succinate synthesis route, which diverts required quantities of NADH through the traditional fermentative pathway and maximizes the carbon converted to succinate by balancing the carbon flux through the fermentative pathway and the glyoxylate pathway (which has less NADH requirement). The synthesis of succinate uses a combination of the two pathways to balance the NADH. Consequently, experimental results indicated that these combined pathways gave the most efficient conversion of glucose to succinate with the highest yield using only 1.25 moles of NADH per mole of succinate in contrast to the sole fermentative pathway, which uses 2 moles of NADH per mole of succinate. A recombinant E. coli strain, SBS550MG, was created by deactivating adhE, ldhA and ack-pta from the central metabolic pathway and by activating the glyoxylate pathway through the inactivation of iclR, which encodes a transcriptional repressor protein of the glyoxylate bypass. The inactivation of these genes in SBS550MG increased the succinate yield from glucose to about 1.6 mol/mol with an average anaerobic productivity rate of 10 mM/h (approximately 0.64 mM/h-OD600). This strain is capable of fermenting high concentrations of glucose in less than 24 h. Additional derepression of the glyxoylate pathway by inactivation of arcA, leading to a strain designated as SBS660MG, did not significantly increase the succinate yield and it decreased glucose consumption by 80%. It was also observed that an adhE, ldhA and ack-pta mutant designated as SBS990MG, was able to achieve a high succinate yield similar to SBS550MG when expressing a Bacillus subtilis NADH-insensitive citrate synthase from a plasmid.

Anaerobiosis↗
PubMed1968

Light-induced changes in the fluorescence yield of chlorophyll a in vivo. I. Anacystis nidulans.

he fluorescence yield of chlorophyll a in dark adapted Anacystis nidulans undergoes a slow change with continuous illumination. After the completion of the initial fast transient, the fluorescence yield rises from the level S to a plateau M within a minute, declining only after prolonged illumination. Both normal and 1,1-dimethyl-3(3'4'-dichloro)-phenylurea (DCMU)-poisoned Anacystis are capable of these changes. In normal Anacystis, the slow increase in the fluorescence yield (S --> M) requires light absorbed in system II while light absorbed in system I is ineffective. In DCMU-poisoned Anacystis, however, these changes are also promoted by light absorbed in system I. Addition of carbonyl cyanide p-trifluoromethoxy phenylhydrazone (FCCP), a photophosphorylation uncoupler acting near the photosynthetic electron transport chain, abolishes the rise from S to M in normal but has no effect in the DCMU-poisoned system. Phlorizin, a phosphorylase inhibitor, has very little effect. These results suggest that the light-induced variation in the fluorescence yield is related to the conformational changes which accompany photophosphorylation. The fluorescence yield of the auxiliary pigment phycocyanin remains constant throughout the interval of the light-induced changes in the fluorescence yield of chlorophyll a. Consequently, the fluorescence spectrum of the alga is variable on continuous illumination.

Antimetabolites↗