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Photoelectron quantum yields of the amino acids.

The photoelectron quantum yields of 21 common amino acids and 15 polyamino acids were measured in the 180-240 nm wavelength region. On the average, the quantum yields of these two groups exhibit quite similar wavelength dependence. For lambda > 220 nm all amino acid and polyamino acid quantum yields are </=10(-7) electrons/(incident) photon. The mean yields increase to about 5 x 10(-7) electrons/photon at 200 nm and 5 x 10(-6) electrons/photon at 180 nm. L-tryptophan, L-tyrosine, and poly-L-tryptophan exhibit above average yields between 180 and 200 nm. Comparison with the dye phthalocyanine indicates that the quantum yield of the dye is two orders of magnitude greater than that of the amino acids from 200 to 240 nm, suggesting the feasibility of photoelectron labeling studies of biological surfaces.

Amino Acids↗

The quantum yield of flash-induced proton release by bacteriorhodopsin-containing membrane fragments.

The quantum yield of proton release by bacteriorhodopsin was measured from volume changes after excitation of purple membrane fragments by short flashes. At low ionic strengths, about 0.25 mol of protons is released per einstein absorbed. This agrees well with quantum yields reported recently for the conversion of bacteriorhodopsin into a metastable state (M) that absorbs near 412 nm. However, the quantum yield of proton release increases gradually with increasing ionic strength; it plateaus with a value of 0.43 +/- 0.03 at ionic strengths above 200 mM. Changing the ionic strength has no detectable effect on the quantum yield of formation of the M spectral state. It thus appears that as many as two protons can be released and rebound in each photochemical cycle at high ionic strengths. The quantum yield of proton release is essentially independent of pH over the range 6.0-8.75. The quantum yield decreases with increasing flash strength, apparently due to photoreversal of the initial photochemical reaction.

Bacteriorhodopsins↗

Temperature-dependent triplet and fluorescence quantum yields of the photosystem II reaction center described in a thermodynamic model.

A key step in the photosynthetic reactions in photosystem II of green plants is the transfer of an electron from the singlet-excited chlorophyll molecule called P680 to a nearby pheophytin molecule. The free energy difference of this primary charge separation reaction is determined in isolated photosystem II reaction center complexes as a function of temperature by measuring the absolute quantum yield of P680 triplet formation and the time-integrated fluorescence emission yield. The total triplet yield is found to be 0.83 +/- 0.05 at 4 K, and it decreases upon raising the temperature to 0.30 at 200 K. It is suggested that the observed triplet states predominantly arise from P680 but to a minor extent also from antenna chlorophyll present in the photosystem II reaction center. No carotenoid triplet states could be detected, demonstrating that the contamination of the preparation with CP47 complexes is less than 1/100 reaction centers. The fluorescence yield is 0.07 +/- 0.02 at 10 K, and it decreases upon raising the temperature to reach a value of 0.05-0.06 at 60-70 K, increases upon raising the temperature to 0.07 at approximately 165 K and decreases again upon further raising the temperature. The complex dependence of fluorescence quantum yield on temperature is explained by assuming the presence of one or more pigments in the photosystem II reaction center that are energetically degenerate with the primary electron donor P680 and below 60-70 K trap part of the excitation energy, and by temperature-dependent excited state decay above 165 K. A four-compartment model is presented that describes the observed triplet and fluorescence quantum yields at all temperatures and includes pigments that are degenerate with P680, temperature-dependent excited state decay and activated upward energy transfer rates. The eigenvalues of the model are in accordance with the lifetimes observed in fluorescence and absorption difference measurements by several workers. The model suggests that the free energy difference between singlet-excited P680 and the radical pair state P680+l- is temperature independent, and that a distribution of free energy differences represented by at least three values of about 20, 40, and 80 meV, is needed to get an appropriate fit of the data.

Kinetics↗

Influences on venom yield in Australian tigersnakes (Notechis scutatus) and brownsnakes (Pseudonaja textilis: Elapidae, Serpentes).

The rates at which venomous animals produce venoms are of obvious biological and medical importance, but factors influencing those rates remain poorly understood. We gathered data on venom yield (wet mass of venom) and percentage solids (dry mass of the venom divided by wet mass) for 53 eastern brownsnakes (Pseudonaja textilis) and 36 mainland tigersnakes (Notechis scutatus) over a 4-year period at Venom Supplies Pty. Ltd, a commercial venom production facility in South Australia. Tigersnakes yielded about threefold more venom (by wet mass) than brownsnakes, but with slightly lower percentage solids. Both species showed significant geographic variation in percentage solids. Venom yields varied as a function of the snake's sex and geographic origin, but these effects were secondary consequences of geographic and sex-based differences in body size. Relative head size affected venom yield in brownsnakes but not tigersnakes. Overall, the amount of venom that a snake produced during milking was affected by its species, its geographic origin, its body size and relative head size, and by the time of year that it was milked, as well as by interactions among these factors. Body size was the most important effect on venom yield, with yields increasing more rapidly with size in brownsnakes than in tigersnakes. Research at the intersection of snake ecology and venom characteristics has great potential, but will require a genuinely interdisciplinary approach.

Animals↗

A study on the venom yield of venomous snake species from Argentina.

A study on the venom yield of snakes from Argentina over a three year period was carried out on adult specimens of Bothrops alternatus (n = 74); Bothrops neuwiedii (n = 127); Bothrops ammodytoides (n = 30); Bothrops moojeni (n = 14); Bothrops jararaca (n = 14); B. jararacussu (n = 6); Crotalus durissus terrificus (n = 120) and Micrurus spp. (n = 6) as well as with 12 specimens of newborn C. d. terrificus kept in captivity. While for each species there was a positive correlation between venom yield and number of snakes milked, the correlation with the snake's body weights after individual milkings was even better, suggesting that the size of the snakes is more important in determining the venom yield than the number of snakes milked or the specimen's sex. Individual milkings indicated that, in addition to the snake size, when the amount of venom is normalized per 100 g body weight there is a species specific difference in venom yield. It follows the order B. jararacussu > B. moojeni approximately = B. jararaca approximately = B. alternatus > B. neuwiedii> Micrurus spp approximately = B. ammodytoides> C. d. terrificus. Although the venom yield per 100 g body weight of newborn C. d. terrificus specimens is 2-fold higher than that of adults, no correlation was observed between venom yield and body weight.

Age Factors↗

Quantitative structure-property relationships for direct photolysis quantum yields of selected polycyclic aromatic hydrocarbons

By the use of partial least squares (PLS) method and 11 quantum chemical descriptors computed by PM3 Hamiltonian, Quantitative Structure-Property Relationships (QSPRs) for direct photolysis quantum yields of selected polycyclic aromatic hydrocarbons (PAHs) were obtained. Direct photolysis quantum yields were predicted for PAHs for which experimental quantum yield values were lacking. Based on the QSPR models, significant PAH molecular characters governing their direct photolysis quantum yields were identified. It can generally be concluded that PAHs with large average molecular polarizability, molecular weight, and heat of formation values tend to have small photolysis quantum yields. PAHs with large values of the energy of the lowest unoccupied molecular orbital (Elumo), small values of the energy of the highest occupied molecular orbital (Ehomo), and large Elumo-Ehomo values, tend to have great photolysis quantum yields.

Journal Article↗

Diagnostic yield of vitrectomy in eyes with suspected posterior segment infection or malignancy.

PURPOSE: To determine the yield of diagnostic pars plana vitrectomy in eyes with suspected posterior segment inflammation or malignancy when clinical examination and systemic laboratory testing did not yield a specific diagnosis. DESIGN: Non-comparative interventional case series PARTICIPANTS: Eighty-seven consecutive patients (90 eyes) who underwent diagnostic pars plana vitrectomy from 1989 through 1999. INTERVENTIONS: Vitreous samples were analyzed in a directed manner based on the preoperative clinical examination and systemic laboratory testing. MAIN OUTCOME MEASURES: Diagnosis from each test performed on the vitreous samples. RESULTS: Diagnostic vitrectomy was performed alone in 6 eyes (7%) and as part of a therapeutic procedure in the remaining 84 eyes. The diagnostic tests performed most frequently included cytopathology (83%), microbiologic culture and sensitivity (43%), polymerase chain reaction (PCR) (36%), and intraocular antibody levels for T. canis (14%). Of these, intraocular antibody testing and PCR had the highest positive yield, 46% and 39%, respectively. Overall, directed vitreous analysis identified a specific cause in 35 eyes (39%). Of the 65 cases in which an underlying infection was suspected preoperatively, the procedure yielded a specific diagnosis in 27 (42%). When intraocular malignancy was considered preoperatively (71 eyes), a diagnosis of intraocular lymphoma was obtained in seven (10%). This difference between these diagnostic yields was significant (P = 0.02, Fisher's exact test). CONCLUSIONS: Diagnostic vitrectomy with directed vitreous fluid analysis yields a specific cause and guides subsequent therapy in a high percentage of cases. This procedure is a valuable adjunct in cases that cannot be diagnosed by less invasive methods.

Adolescent↗

Effects of elevated carbon dioxide and ozone on the growth and yield of potatoes (Solanum tuberosum) grown in open-top chambers.

Potato (Solanum tuberosum cv. Bintje) was grown in open-top chambers under three carbon dioxide (ambient and seasonal mean concentrations of 550 and 680 mumol mol-1 CO2) and two ozone concentrations (ambient and an 8 h day-1 seasonal mean of 50 nmol mol-1 O3) between emergence and final harvest. Periodic non-destructive measurements were made and destructive harvests were carried out at three key developmental stages (24, 49 and 101 days after emergence) to establish effects on growth and tuber yield. Season-long exposure to elevated O3 reduced above-ground dry weight at final harvest by 8.4% (P < 0.05), but did not affect tuber yields. There was no significant interaction between CO2 and O3 for any of the growth and yield variables examined. Non-destructive analyses revealed no significant effect of elevated CO2 on plant height, leaf number or green leaf area ratio. However, destructive harvests at tuber initiation and 500 degrees Cd after emergence showed that above-ground dry weight (8 and 7% respectively) and tuber yield (88 and 44%) were significantly increased (P < 0.05) in the 550 mumol mol-1 CO2 treatment. Responses to 550 and 680 mumol mol-1 CO2 were not significantly different for most parameters examined, suggesting the existence of an upper limit to the beneficial influence of CO2 enrichment. Significant effects on above-ground dry weight and tuber yield were no longer apparent at final harvest, although tuber numbers were increased (P < 0.05) under elevated CO2, particularly in the smaller size categories. The results show that the O3 treatment imposed was insufficient to reduce tuber yields and that, although elevated CO2 enhanced crop growth during the early stages of the season, this beneficial effect was not sustained to maturity.

Agriculture↗

Lack of correlation between cigarette mainstream smoke particulate phase radicals and hydroquinone yield.

Evidence suggests that when compared with non-smokers, cigarette smokers are exposed to an increased burden of free radicals from both the vapor phase and particulate phase of the cigarette smoke aerosol. In this study, primary emphasis was placed on the free radicals found in the particulate phase. Published reports hypothesize that the particulate phase free radicals of cigarette mainstream smoke (MS) condensate consist of a hydroquinone/semiquinone/quinone shuttle. However, our results do not suggest that there is a positive correlation between the smoke yield of hydroquinone and the presence of particulate phase free radicals. First, 10-fold reductions in MS hydroquinone yield were obtained when KNO3 was applied to the surface of tobacco of an American blended cigarette. Surprisingly, there was no significant corresponding change in the yield of particulate phase radicals. Second, in experiments testing MS from low and high hydroquinone-yielding tobaccos there was no consistent corresponding relationship between hydroquinone and particulate phase radical yields. In one series of blends there was at best an inverse relationship between hydroquinone and particulate phase radical yields. In contrast with the published literature, we conclude that the particular compound or compounds driving particulate phase free radical formation are currently unknown. An additional experiment reported here suggested that components of the water soluble extract of burley tobacco may be driving the formation of particulate phase free radicals.

Antioxidants↗

Comparative evaluation of the effect of a high yield criteria list upon skull radiography.

Based on results of studies using high yield criteria to determine the need for skull radiography, the Utilization Review Committee of the University Hospital (UH), University of Washington, Seattle implemented a policy encouraging use of the criteria in ordering skull radiology. The Bureau of Radiologic Health of the FDA supported a project comparing skull radiology use patterns at UH, with the high yield criteria policy, and Harborview Medical Center (HMC), without a policy. Results showed an increase of around 60% at HMC since the 1972--73 academic year. At UH, there was a decrease of 40% since the 1972--73 academic year. At HMC a medical record review showed only 51 positive reports that significantly contributed to patient care, about the same rate observed in 1967. At the UH, only nine positive reports significantly contributed to patient care, with 62% compliance with the high yield criteria. A current demonstration project under the auspices of the Washington State Professional Standards Review Organization and Bureau of Radiologic Health involves implementing the high yield criteria list at both HMC and UH. After three months, out of 6,003 patient visits, skull radiography was deemed necessary in 518 cases. Of this total 181 had high yield criteria checked. There were 37 positive reports out of these and 23 examinations that made a documented significant contribution to patient care. In the group without high yield criteria, 434 cases, there were 22 positive reports but no significant contribution to patient care documented after four weeks.

Craniocerebral Trauma↗

High body weight gain and reduced bovine mammary growth: physiological basis and implications for milk yield potential.

Available evidence concerning the relationship between growth rate, mammary growth and milk yield in heifers leads to these conclusions: 1) Increased growth rate due to high feeding level before puberty onset can lead to reduced pubertal mammary growth and reduced milk yield potential. 2) Increased growth rate due to high feeding level after puberty and during pregnancy have no effect on mammary growth and milk yield. 3) Higher body weight gain due to higher genetic potential for growth is positively related to milk yield. The negative effect of high feeding level before puberty occurs in all breeds, but the level of feeding causing reduced yield varies. Variation in responses between experiments suggests that feeding regimes that support high growth rates without negative effect on yield can be developed. A breakthrough most likely will originate from increased knowledge of the physiological relationship between nutrition and mammary development. Our investigations suggest that blood growth hormone (GH) is important for mammary development, and that the negative effect of high feeding level on mammary development may be due to reduced blood GH. GH, however, does not bind to mammary tissue. Experiments with exogenous GH suggest that GH acts on mammary tissue via IGF-I, but IGF-I is increased by high feeding level - not decreased as GH. This paradoxical relationship cannot be explained by changes in circulating IGF binding proteins. However, the sensitivity of mammary tissue to IGF-I is reduced by high feeding level, probably due to the action of locally produced binding proteins and/or growth factors.

Animal Nutritional Physiological Phenomena↗

Effects of Alternaria triticina and foliar fly ash deposition on growth, yield, photosynthetic pigments, protein and lysine contents of three cultivars of wheat.

A greenhouse experiment was conducted to study the effects of Alternaria triticina with and without foliar dusting of fly ash (0.0, 2.5, 5.0, 7.5 g plant(-1)/day(-1)) on the growth, yield, photosynthetic pigments, protein and lysine contents of three cultivars of wheat, Triticum aestivum. Dusting of 2.5 and 5.0 g fly ash caused a significant increase in growth, yield, photosynthetic pigments, protein and lysine contents of all the three cultivars. Dusting of 5.0 g fly ash caused a higher increase in the parameters than the 2.5 g dusting. However, dusting of 7.5 g fly ash had an adverse effect on growth, yield, photosynthetic pigments, protein and lysine contents. Cultivar HD-2009 suffered highest reductions in growth and yield and showed greater infected leaf area and disease symptoms from A. triticina followed by HD-2329 and Lok-1. Inoculation of A. triticina to plants dusted with 2.5/5.0 g fly ash gave higher reduction in growth and yield than did plants inoculated with A. triticina without fly ash. Cultivar Lok-1 showed highest growth, yield, photosynthetic pigments, protein and lysine contents followed by HD-2329 and HD-2009.

Air Pollutants↗

Improved yield and stability of L49-sFv-beta-lactamase, a single-chain antibody fusion protein for anticancer prodrug activation, by protein engineering.

The L49 single-chain Fv fused to beta-lactamase (L49-sFv-bL) combined with the prodrug C-Mel is an effective anticancer agent against tumor cells expressing the p97 antigen. However, large-scale production of L49-sFv-bL from refolded E. coli inclusion bodies has been problematic due to inefficient refolding and instability of the fusion protein. Sequence analysis of the L49-sFv framework regions revealed three residues in the framework regions at positions L2, H82B, and H91, which are not conserved for their position, occurring in <1% of sequences in Fv sequence databases. One further unusual residue, found in <3% of variable sequences, was observed at position H39. Each unusual residue was mutated to a conserved residue for its position and tested for refolding yield from inclusion bodies following expression in E. coli. The three V(H) single mutants showed improvement in the yield of active protein and were combined to form double and triple mutants resulting in a 7-8-fold increased yield compared to the parental protein. In an attempt to further improve yield, the orientation of the triple mutant was reversed to create a bL-L49-sFv fusion protein resulting in a 3-fold increase in expressed inclusion body protein and producing a 20-fold increase in the yield of purified protein compared to the parental protein. The triple mutants in both orientations displayed increased stability in murine plasma and binding affinity was not affected by the introduced mutations. Both triple mutants also displayed potent in vitro cytotoxicity and in vivo antitumor activity against p97 expressing melanoma cells and tumor xenografts, respectively. These results show that a rational protein-engineering approach improved the yield, stability, and refolding characteristics of L49-sFv-bL while maintaining binding affinity and therapeutic efficacy.

Animals↗

Conventional and high-yield synthesis of DTPA-conjugated peptides: application of a monoreactive DTPA to DTPA-D-Phe1-octreotide synthesis.

Successful imaging of somatostatin receptor-positive tumors with 111In-DTPA-D-Phe1-octreotide has stimulated development of peptide radiopharmaceuticals using DTPA as the chelating agent. However, use of cyclic DTPA dianhydride (cDTPA) resulted in low synthetic yields of DTPA-peptide by either solution or solid-phase syntheses. This paper reports a novel high-yield synthetic procedure for DTPA-D-Phe1-octreotide that is applicable to other peptides of interest using a monoreactive DTPA derivative. A monoreactive DTPA that possesses one free terminal carboxylic acid along with four carboxylates protected with tert-butyl ester (mDTPA) was synthesized. Fmoc-Thr(tBu)-ol, prepared from Fmoc-Thr(tBu)-OH, was loaded onto 2-chlorotrityl chloride resin. After construction of the peptide chains by Fmoc chemistry, mDTPA was coupled to the alpha amine group of the peptide on the resin in the presence of 1,3-diisopropylcarbodiimide and 1-hydroxybenzotriazole. Treatment of the mDTPA-peptide-resin with trifluoroacetic acid-thioanisole removed the protecting groups and liberated [Cys(Acm)2,7]-octreotide-D-Phe1-DTPA from the resin. Iodine oxidation of the DTPA-peptide, followed by the reversed-phase HPLC purification, produced DTPA-D-Phe1-octreotide in overall 31.8% yield based on the starting Fmoc-Thr(tBu)-ol-resin. The final product gave a single peak on analytical HPLC, and amino acid analysis and mass spectrometry confirmed the integrity of the product. 111In radiolabeling of the product provided 111In-DTPA-D-Phe1-octreotide with > 95% radiochemical yield, as confirmed by analytical reversed-phase HPLC, TLC, and CAE. These finding indicated that use of mDTPA during solid-phase peptide synthesis greatly increased the synthetic yield of DTPA-D-Phe1-octreotide, due to the absence of nonselective reactions that are unavoidable when cDTPA is used. These results also suggested that mDTPA would be a versatile reagent to introduce DTPA with high yield into peptides of interest.

Octreotide↗

O2 and CO reactions with heme proteins: quantum yields and geminate recombination on picosecond time scales.

Picosecond time-resolved absorption spectroscopy and low-temperature studies have been undertaken in order to understand the nature of the intrinsic quantum yields and geminate recombination of carbon monoxide and oxygen to hemoglobin and myoglobin. We find that the photoproduct yields at 40 ps and long times (minutes) after photolysis at 8 K are similar; however, the yield of oxygen photoproducts is 0.4 +/- 0.1 while the yield of carbon monoxide photoproducts is 1.0 +/- 0.1 for both myoglobin and hemoglobin. Measurements in the Soret, near-infrared, and far-IR are used to quantitate the photoproduct yields. These results call into question previous cryogenic kinetic studies of O2 recombination. Significant subnanosecond geminate recombination is observed in oxyhemoglobin down to 150 K, while below 100 K this geminate recombination disappears. The lower photoproduct yields for oxyheme protein complexes can be attributed to both subnanosecond and subpicosecond recombination events which are ligand and protein dynamics dependent.

Animals↗

Optimization of the human adenosine A2a receptor yields in Saccharomyces cerevisiae.

G-protein coupled receptors (GPCRs) have been implicated in many human diseases and have emerged as important drug targets. Despite their medical relevance, knowledge about GPCR structure is limited, mainly due to difficulties associated with producing large amounts of functional protein and isolating this protein in functional form. However, our previous results indicate that when the human adenosine A(2)a receptor (A(2)aR) is expressed in Saccharomyces cerevisiae, high yields can be achieved. In light of these initial results and in anticipation of future purification efforts, experiments were conducted to optimize the system for maximum total protein yield. Emphasis was placed on not only producing large quantities of A(2)aR in each cell but also achieving high cell density in batch culture. Therefore, temperature, media pH, inducer concentration in the media, and induction cell density were tested for their effects on both cell growth (as measured by optical density, OD(600)) and per cell A(2)aR expression levels. For these studies, the A(2)aR expression levels were determined using a previously described A(2)aR-green fluorescent protein (GFP) fusion, so that expression could be monitored by fluorescence. Overall the data indicate that at late times ( approximately 60 h of expression) approximately 75% higher total batch protein yields can be achieved using lower expression temperatures or 60% higher using elevated induction cell density. The highest yields correspond to approximately 28 mg per liter of culture of total A(2)aR. Amounts of functional receptor were shown to increase on a per cell basis by decreasing expression temperature up to 25 h of expression, but at late time points ( approximately 60 h) functional yields did not appreciably improve. When compared to other reports of GPCR expression in yeast it is clear that this system is among those producing the highest GPCR protein yields per culture both before and after optimization.

Biotechnology↗

Correlation of fermentation yield with yeast extract composition as characterized by near-infrared spectroscopy

Complex, ill-defined mixtures of natural origin are often used as nutrients in the production of biological products through microbial fermentation. Product yields are affected by variation in these natural products. It was desired to examine near-infrared spectroscopy as a rapid screening tool for qualifying raw material lots. Specifically, the characterization of yeast extract was investigated. The model system consisted of a Merck & Co., Inc., microbial fermentation process. Cell mass and specific product yields are dependent upon variations in the yeast extract used in the medium. Partial least-squares regression on the second-derivative spectral absorbances of various yeast extracts in the ranges 1150-1380, 1554-1826, and 2100-2300 nm resulted in the development of models with multiple correlation coefficients of 0.99 for cell mass yields and 0.96 for specific product yields in large-scale fermentations. These models could also be used to predict cell mass yields in 15 L batch fermentations and specific product yields in 2-L shake flasks.

Journal Article↗

Secondary organic carbon and aerosol yields from the irradiations of isoprene and alpha-pinene in the presence of NOx and SO2.

A laboratory study was carried out to investigate the secondary organic carbon (SOC) yields of alpha-pinene and isoprene in the presence of SO2, which produces acidic aerosol in the system. Experiments were based on irradiating each hydrocarbon (HC) with NOx in a 14.5 m3 smog chamber operated in the dynamic mode. The experimental design consisted of several multi-part experiments for each HC. In the first part of each experiment, an HC/NOx irradiation was conducted in the absence of SO2 and was followed by irradiations with the addition of SO2 in subsequent parts. Filter-based analyses for organic carbon were made using a thermal-optical approach either with an off-line instrument or in situ with an automated instrument. For isoprene in the absence of SO2, the SOC yield was approximately 0.001, a value consistent with earlier work from this laboratory. With the addition of up to 200 ppb SO2, the yield increased by a factor of 7. For alpha-pinene in the absence of SO2, the SOC yield of the irradiated mixture was found to average 0.096 from two experiments. With SO2 in the system, the SOC yield increased on average to 0.132. These results suggest that SO2, and by inference acidic aerosol, may play a role in increasing the yield of SOC from the photooxidation products of biogenic hydrocarbons or by the direct uptake of biogenic hydrocarbons onto acidic aerosol.

Aerosols↗