Potassium Acetate Buffer Research Articles

Synthesis and Structure of Asymmetric Zirconium-Substituted Silicotungstates, [Zr6O2(OH)4(H2O)3(β-SiW10O37)3]14- and [Zr4O2(OH)2(H2O)4(β-SiW10O37)2]10-

The reaction of ZrCl4 with [gamma-SiW10O36]8- in a potassium acetate buffer results in two different products depending on the reactant ratios. The trimeric species [Zr6O2(OH)4(H2O)3(beta-SiW10O37)3]14- (1) consists of three beta23-SiW10O37 units linked by an unprecedented Zr6O2(OH)4(H2O)3 cluster with C1 point group symmetry. The dimeric species [Zr4O2(OH)2(H2O)4(beta-SiW10O37)2]10- (2) consists of beta22- and beta12-SiW10O37 units sandwiching a Zr4O2(OH)2(H2O)4 cluster, which also has C1 symmetry. Polyanion 1 contains more zirconium centers than any other polyoxometalate known to date.

HPLC quantification of metoprolol with solid-phase extraction for the drug monitoring of pediatric patients.

Although the analytical literature seems abundant for the determination of metoprolol in human plasma, a method using standard equipment providing a sensitive and simple high-performance liquid chromatographic (HPLC) method for limited blood volume, e.g. where 1 mL of blood in a 1 kg infant equals 70 mL of adult blood volume, has rarely been addressed. Therefore, in 500 microL of plasma, metoprolol was extracted using an internal standard and solid-phase extraction columns. Chromatographic analysis was performed on a Spherisorb C(6) column (5 microm particle size) at ambient temperature and fluorimetric detection with an excitation wavelength of 225 nm, and emission wavelength of 310 nm. The mobile phase [30% acetonitrile and 70% 0.25 m potassium acetate buffer (pH 4)] was pumped with 1 mL/min. Metoprolol recovery was determined at 73.0 +/- 20.5%, and the limit of quantitation was 2.4 ng/mL. Precision values of intra- and inter-assay were below 15.5% and those for accuracy were between 90 and 110%. This method was developed for monitoring and determination of pharmacokinetic parameters of metoprolol in pediatric patients and therefore metoprolol plasma concentrations in a 2-year-old child with ventricular tachycardia are reported. .

Preparation, electrochemistry and crystal structure of a derivative of 18-tungstophosphate with Dawson structure: K 16H[Yb(α-2-P 2W 17O 61) 2]·44H 2O

The heteropolyanion [Yb(α-2-P 2W 17O 61) 2] 17− has been isolated as a potassium salt in ∼30% yield by five-day decreasing temperature-programmed from 60 °C to room temperature, in a potassium acetate buffer, formed by reaction of K 6P 2W 18O 62·10H 2O with Yb(NO 3) 3 and characterized by IR, UV spectra. Single crystal X-ray structural analysis of K 16H[Yb(α-2-P 2W 17O 61) 2]·44H 2O (triclinic, space group PI a=14.499(3), b=22.433(5), c=24.505(5) Å, α=95.36(3), β=102.67(3), γ=100.06(3)°, Z=2, 24,089 independent reflections, R 1=0.0497) reveals that two chemically identical [α-2-P 2W 17O 61] 10− moieties are connected through one Yb atom, which is in a square antiprismatic coordination environment with eight oxygen atoms, four from each of the two [α-2-P 2W 17O 61] 10− moieties. The Yb(III) ion substitutes for two [W=O] 4+ units in the ‘cap’ regions of the tungsten–oxygen frameworks of the two parent Wells–Dawson ions. The point group symmetry of the title polyanion is C 2. In the extensive pH region from 10.5 to 1.60, the cyclic voltammograms for the title compound in the presence of 0.5 M NaCl aqueous solution as supporting electrolyte mainly illustrate nearly reversible one-electron reduction processes. The results of the thermogravimetric analysis of the title compound show one one-step slow weight loss and the framework decomposition of the polyanion in the title compound is at 560.0 °C.

Enzymatic Hydrolysis of Organic Phosphorus in Swine Manure and Soil

Organic phosphorus (Po) exists in many chemical forms that differ in their susceptibility to hydrolysis and, therefore, bioavailability to plants and microorganisms. Identification and quantification of these forms may significantly contribute to effective agricultural P management. Phosphatases catalyze reactions that release orthophosphate (Pi) from Po compounds. Alkaline phosphatase in tris-HCl buffer (pH 9.0), wheat (Triticum aestivum L.) phytase in potassium acetate buffer (pH 5.0), and nuclease P1 in potassium acetate buffer (pH 5.0) can be used to classify and quantify Po in animal manure. Background error associated with different pH and buffer systems is observed. In this study, we improved the enzymatic hydrolysis approach and tested its applicability for investigating Po in soils, recognizing that soil and manure differ in numerous physicochemical properties. We applied (i) acid phosphatase from potato (Solanum tuberosum L.), (ii) acid phosphatases from both potato and wheat germ, and (iii) both enzymes plus nuclease P1 to identify and quantify simple labile monoester P, phytate (myo-inositol hexakis phosphate)-like P, and DNA-like P, respectively, in a single pH/buffer system (100 mM sodium acetate, pH 5.0). This hydrolysis procedure released Po in sequentially extracted H2O, NaHCO3, and NaOH fractions of swine (Sus scrofa) manure, and of three sandy loam soils. Further refinement of the approach may provide a universal tool for evaluating hydrolyzable Po from a wide range of sources.

Chemical Reactivity of Ro-26-9228, 1α-Fluoro-25-hydroxy-16,23E-diene-26,27-bishomo-20-epi-cholecalciferol in Aqueous Solution

2The degradation of Ro‐26‐9228, 1α‐fluoro‐25‐hydroxy‐16,23E‐diene‐26,27‐bishomo‐20‐epi‐cholecalciferol, , was studied in aqueous solution in the pH range of 1.17–10.56 and in alcohol solutions, at 25, 40, and 50°C. The degradation of Ro‐26‐9228 was found to be acid catalyzed and to be independent of potassium acetate buffer concentration. Above pH 4, the reaction rate is independent of pH, with a T90 of 14.3h at 25°C in pH 7.75 buffer. 19F nuclear magnetic resonance was used to study the ratio of the vitamin (6‐s‐trans) to previtamin form in acetonitrile at 40°C. The equilibrium percentage of previtamin and the rate of approach to equilibrium were 13.8% and 0.2 h−1, respectively. Nuclear magnetic resonance was used to elucidate the structure of the degradation products. Novel products were formed from the elimination of the fluorine and addition of solvent to C9, with formation occurring through the previtamin form. Additional degradation products result from reaction of the side chain 25‐hydroxyl and addition of solvent to C1. © 2003 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:1981–1989, 2003

Determination of methylnaltrexone in clinical samples by solid-phase extraction and high-performance liquid chromatography for a pharmacokinetics study

A high-performance liquid chromatographic (HPLC) method with electrochemical detection and solid-phase extraction (SPE) using cartridges of weak cation-exchange capacity as the primary retention mechanism is described for the separation and determination of methylnaltrexone (MNTX) in small clinical samples of plasma or urine. The procedure was performed using a Phenomenex Prodigy ODS-2, 5 μm, 150×3.2 mm analytical column and 50 m M potassium acetate buffer, with 11% methanol as organic modifier at pH* 4.5 at a flow-rate of 0.5 ml/min. The detection potential was 700 mV. The six-point standard calibration curves were linear over three consecutive days in the range from 2 to 100 ng/ml. The average goodness of fit ( r) was 0.9993. The lower limit of detection (LOD) and limit of quantification (LOQ) were found to be 2.0 and 5.0 ng/ml, respectively. At the LOQ, the coefficient of variation for the entire method was 8.0% and the accuracy was 10.0% ( n=10). Recovery of the drug from plasma was in the region of 94%. The method was applied to a pharmacokinetics study of methylnaltrexone after subcutaneous administration and in numerous assays of analytes in blood plasma and urine. The pharmacokinetics parameters for a single dose of 0.1 or 0.3 mg/kg in plasma were C max=110 (±55) and 287 (±101) ng/ml and t max=16.7 (±10.8) and 20.0 (±9.5) min, respectively. The method is simple, yet sensitive for the detection and determination of methylnaltrexone in biological samples at the level of the physiological response.

HPLC quantification of carvedilol in small plasma volumes from children

A sensitive high-performance liquid chromatographic method has been developed for the determination of the β-receptor blocker carvedilol in small volumes of plasma from pediatric patients. Carvedilol and the internal standard naftopidil were extracted from only 300 μL plasma with solid-phase extraction columns and eluted with a mixture of 80% (v/v) acetonitrile and 20% (v/v) potassium acetate buffer (0.1 M, pH 5). Analysis of the extracts was performed on a Spherisorb C6 column with a mobile phase of 65% acetonitrile, 35% potassium acetate buffer (0.25 M, pH 4) and fluorescence detection. Carvedilol and the internal standard showed recoveries of 87.0±13.9% and 97.7±18.0% respectively (n=75, each; values are means±standard deviations). The analysis of carvedilol was linear over a range of 0.40–242 ng mL−1, the limit of quantification was 0.40 ng mL−1. As an application of the assay, a profile of plasma concentrations versus time of a six-month-old patient is reported.

Determination of carvedilol in human cardiac tissue by high-performance liquid chromatography.

A new high-performance liquid chromatographic method has been developed for the determination of the beta-receptor blocker carvedilol in human cardiac tissue. After homogenizing tissue samples in a microdismembrator, carvedilol and the internal standard naftopidil are extracted with acetone. The extract is evaporated to dryness and reconstituted in a potassium acetate buffer of pH 3.5. Samples are cleaned up with solid-phase extraction columns. Carvedilol and the internal standard show recoveries of 69.8 +/- 12.2% and 63.9 +/- 9.34%, respectively. The linearity range for carvedilol is 0.01-0.35 ng/mg (parts per billion) tissue (wet weight), and the limit of quantitation is 0.01 ng/mg. The percentage coefficient of variation of the intra-assay varies between 1.45 and 5.38% and the interassay between 4.25 and 6.96%. To use as an application of the assay, the cardiac carvedilol tissue level in a patient on oral carvedilol therapy for congestive heart failure is reported.

Determination of oxalate by the single drop method using an electrodeless piezoelectric quartz crystal.

The single drop method using an electrodeless piezoelectric quartz crystal (PQC) was able to be applied to the determination of oxalate, in the form of calcium oxalate, in spinach extract. Setting an electrodeless quartz plate, which was treated with paraffin, on the copper plate electrode in a cell, a drop of 5 μl of calcium chloride solution containing potassium chloride and acetate buffer was applied. A platinum wire of a counter electrode was inserted into the drop at 1.0 mm distance between the plate and the top of the wire electrode, and the system was left until the oscillation frequency of the electrodeless PQC became constant. The oxalate sample solution of 5 μl containing potassium chloride and acetate buffer was then added to the drop. By reading the frequency change between just after the application of the sample solution and at 3 min later, the concentration of oxalate was estimated. Oxalate in spinach leaves was extracted with hot water by boiling for 20 min. After passing through a filter paper, the extract was added to acetic acid and incubated over night. Then the extract was filtrated using a membrane filter, and to it was added potassium chloride and sodium acetate to adjust the pH to 4.6. This solution was used as the sample. The concentration of oxalate in the spinach leaves estimated by this method was in agreement with that obtained by ion chromatography.

Enantioselective determination of DN-2327, a novel non-benzodiazepine anxiolytic, and/or its active metabolite in human plasma and urine using high-performance liquid chromatography.

A new rapid, specific and sensitive reversed-phase HPLC method has been developed for simultaneous measurement of the R- and S-enantiomers of DN-2327 (I), a novel non-benzodiazepine anxiolytic, and those of its pharmacologically active metabolite, MII (II), in human plasma or urine. Extraction of all the enantiomers and internal standard was achieved using solid-phase extraction on C8 columns. Resolution was achieved using a Chiral-AGP column with mobile phase comprising 6.5% (v/v) acetonitrile in 50 mM potassium acetate buffer, pH *q3 3.10, at typical flow-rates of 0.35 ml/min for plasma and 1.0 ml/min for urine assays. Fluorescence detection was employed using excitation and emission maxima of 328 and 367 nm, respectively. Analytes were well resolved and no interfering endogenous peaks were observed either from plasma or urine. Standard curves for urine were linear for concentrations up to 500 ng/ml for R- and S-II, with correlation coefficients higher than 0.994 and limit of quantitation (LOQ) of 1 ng/ml for each enantiomer. The LOQ in plasma was 0.1 ng/ml for each of the four enantiomers. The precision and accuracy of the method for the enantiomers of both I and II were good for plasma and urine with coefficients of variations typically within 10%. The stability of the R- and S-enantiomers of II and I in plasma and those of II in urine was excellent, with no evidence of degradation or interconversion during storage and handling.

Mechanism of alterations in isolated rat liver mitochondrial function induced by gold complexes of bidentate phosphines.

Au(DPPE)+2 (bis[1,2-bis(diphenylphosphino)ethane] gold(I] is an organo-gold antineoplastic agent that has anti-tumor activity in a variety of in vitro cell lines and in vivo rodent tumor models. Preliminary studies suggested that this compound represented a novel class of inhibitors of mitochondrial function. The purpose of this study was, therefore, to determine the mechanism of mitochondrial dysfunction induced by Au(DPPE)+2. Au(DPPE)+2 induced a rapid, dose-related collapse of the inner mitochondrial membrane potential (EC50 = 28.0 microM) that was not potentiated by Ca2+ preloading. Au(DPPE)+2-induced dissipation of mitochondrial membrane potential was accompanied by an efflux of Ca2+ from mitochondria upon exposure to Au(DPPE)+2. Ca2+ efflux in these experiments was via a reversal of the Ca2+ uniporter as efflux could be inhibited with ruthenium red. Au(DPPE)+2 did not increase the permeability of mitochondria to oxalacetate, indicating that the collapse of membrane potential may not be a result of gross increased inner membrane permeability. However, Au(DPPE)+2 may mediate an increased permeability of the inner membrane to cations and protons. Au(DPPE)+2 caused passive swelling in potassium acetate buffer in the absence of valinomycin, suggesting Au(DPPE)+2 facilitated the exchange of H+ and K+. Ca2+ cycling was not extensive and did not contribute to the decrease in membrane potential. These data suggest that one possible mechanism of Au(DPPE+2-induced uncoupling of mitochondrial oxidative phosphorylation is via increased permeability of the inner mitochondrial membrane to cations. The disruption of mitochondrial function may be a key process leading to hepatocyte cell injury by this drug.

Purification and Characterization of Tissue-Type Plasminogen Activator in Maxillary Mucosa with Chronic Inflammation

Tissue-type plasminogen activator (TPA) was purified from maxillary mucosa with chronic inflammation and compared with urokinase. Purification procedure consisted of the extraction from delipidated mucosa with 0.3M potassium acetate buffer (pH 4.2), 66% saturation of ammonium sulfate, zinc chelate-Sepharose, concanavalin A-Sepharose and Sephadex G-100 gel filtration chromatographies. The molecular weight of the TPA was approximately 58,000 +/- 3,000. Its activity was enhanced in the presence of fibrin and was quenched by placental urokinase inhibitor, but not quenched by anti-urokinase antibody. The TPA made no precipitin line against anti-urokinase antibody, while urokinase did. All these findings indicate that the TPA in maxillary mucosa with chronic inflammation is immunologically dissimilar to urokinase and in its affinity for fibrin.

Determination of trimecaine metabolites in blood plasma by capillary isotachophoresis

A method is proposed for the determination of trimecaine (diethylglycylmesidide) and its de-ethylated metabolites (monoethylglycylmesidide and glycylmesidide) in blood plasma by capillary isotachophoresis. The deproteinated plasma is extracted into chloroform after alkalinization and the total solids in the organic layer are dissolved in acidified 25% 2-propanol. Subsequent isotachophoretic analysis is performed in an operational system consisting of potassium acetate buffer (pH 4.75) as the leading and β-alanine as the terminating electrolyte. The order of the zones corresponds to the molecular weights of the separated compounds. The recovery of all substances of interest is 55% and the limit of determination is 0.05 μg of each substance in 1 ml of plasma.

Rapid high-pressure liquid chromatographic method for analysis of phenoxymethylpenicillin in human serum.

A selective high-pressure liquid chromatographic method for the determination of phenoxymethylpenicillin in human serum is described. The technique is based on the single extraction of the drug from acidified serum with diethyl ether. Chloramphenicol is used as internal standard. The chromatographic system consists of a reversed-phase C-18 column; the mobile phase is acetonitrile-0.01 M potassium acetate buffer (20:80 [vol/vol]; pH 6.5). The method can accurately measure serum penicillin concentrations down to 30 micrograms/liter with 500 microliter of sample. The coefficient of variation for intraassay variability of penicillin is between 1.5 and 4.9% in the range of 0.125 to 16.00 mg/liter. The extraction efficiency is 78.5 +/- 6.8% (+/- standard deviation; n = 9), and the calibration graph is linear in the concentration range studied. Pharmacokinetic data, obtained with the present method from seven healthy volunteers, are presented.

Partial Purification of an Ethylene-binding Component from Plant Tissue

An ethylene binding component(s) has been partially purified from mung bean sprouts. Tissue was homogenized in 0.3 molar sucrose and 0.2 molar potassium phosphate buffer (pH 7.0). The homogenate was centrifuged, and resuspended fractions were assayed by incorporating them onto cellulose fibers (0.7 grams per milliliter). These were exposed to [(14)C]ethylene (3.7 x 10(-2) microliters per liter of 120 millicurie per millimole) in the presence or absence of 1000 microliters per liter unlabeled ethylene. The cellulose was transferred to separate containers and the [(14)C]ethylene was absorbed in mercury perchlorate and counted. Distribution of ethylene binding to various fractions was: 0 to 3,000g, 3%; 3,000 to 12,000g; 4%; 12,000 to 100,000g, 69%; cellular debris, 24%; 100,000g supernatant, 0%. Adjustment of the pH to 4.0 precipitates the ethylene-binding component. Neutralization, addition of Triton X-100, and readjustment of the pH to 4.0 "solubilized" most of the binding component. Further purification was obtained by chromatography on CM-Sephadex in 10 millimolar potassium acetate buffer, (pH 5.0) containing 1% Triton X-100. Elution was with 200 millimolar potassium phosphate (pH 6.0) containing 1% Triton X-100. Upon treatment of the Triton "solubilized" component with cold acetone, over 90% of the binding capacity was lost. Extraction of the acetone-precipitated residue with 2% Triton X-100 restored some of the binding capacity which was found in the soluble fraction. The pH optimum for binding is 6.0. Passing the Triton X-100 extract of the acetone powder through Sepharose 6B provides considerable purification. The binding component moved ahead of most of the protein.

Purification and partial characterization of plasminogen activator from human uterine tissue

A procedure was developed for the purification of a plasminogen activator from human uterine tissue. It involves six consecutive steps: (1) extraction of the plasminogen activator from delipidated uterine tissue with 0.3 M potassium acetate buffer, pH 4.2; (2) ammonium sulphate precipitation; (3) zinc chelateagarose chromatography; (4) n-butyl-agarose chromatography; (5) concanavalin A-agarose chromatography, and (6) gel filtration on Sephadex G-150. The specific activity of the final plasminogen activator preparation was increased by a factor 4500 as compared with the crude extract. The purified plasminogen activator showed a strong tendency to adsorb to surfaces. This could be effectively prevented by Tween-80. The molecular weight of the plasminogen activator was 64 000 as estimated by gel filtration in 1.0 M NaCl and 69 000 as estimated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The plasminogen activator consisted of two chains (molecular weights 31 000 and 38 000) connected by disulphide bridges. The smallest chain contained the serine residue of the active site as deduced from the incorporation of the tritium label of [ 3H]diisopropylphosphofluoridate.

Anodic Wave Polarography of Oxalate Ion

The polarographic behavior of oxalate ion, which forms an insoluble salt with mercurous ion has been studied in neutral and acidified potassium nitrate and acetate buffer solutions. In neutral and slightly acidified solution, oxalate ion produces a three-step anodic wave. The first (I) and the second (II) are attributed to the phenomenon that a mono-molecular film of mercurous oxalate are formed by the oxidation of mercury. Peculiarities of the anodic wave are as follows: 1) The limiting current rises with the remarkable abruptness. Changes of 6 mV for the wave (I) and 7 mV for the wave (II) are resulted for the limiting currents to become fully developed.2) The addition of oxalate ion shifts the starting potential of the waves (I) and (II) to less positive value but does not change the limiting currents.3) The temperature coefficients of the height of the waves (I) and (II) are relatively small.4) The limiting current is proportional to the corrected pressure of mercury, and the icorr. td, value remains constant at 1.36 ± 0.03 μC for the wave (I) and 3.21 ± 0.07 μC for the wave (II). Therefore, by assuming the formation of a monomolecular film of Hg2(COO)2, the area per molecule is calcu- lated to be 68.6 A2 for the wave (II) and 28.8 A2 for the (II) respectively.5) Electrocapillary curves show that a remarkable change in the interfacial tention occurs in the potential range of the limiting current of the wave (I).From the results above, it is concluded that they are both absorption waves. As the third wave appears just before the appearance of dissolution wave of mercury, it is difficult to elucidate the electrode reaction.The anodic wave of oxalate ion is remarkably affected by the addition of small amounts of halogen ions. The first wave shifts to more negative potential and a new maximum appears just after the second wave. The height of the maximum is proportional to the halogen ion concentration. Therefore, the method is found to be suitable for the determination of halogen ion at the concentration range of 10-5 mol/l.

The effect of cathepsins from varied sources on proteinpolysaccharide (PP-L) of bovine costal cartilage and on proteoglycan subunit (PGS) of bovine nasal cartilage.

The death of the hypertrophic cartilage cells of epiphyseM plates may be causally linked to the provisional calcification of extraterritorial matrix in the vicinity of such cells. An increasing number of cytoplasmic organelles, limited by a single membrane and morphologically identified as lysosomes are found in maturing chondrocytes (8). Moreover, when the hypertrophic cells degenerate, the marker enzyme for lysosomes, acid phosphatase, is seen in the adjacent cartilage matrix (1, 4). Among the complement of enzymes in lysosomes there are acid proteases. These have been implicated as playing a role in the modification of eartilagenous matrices (3, 7, 9). On the other hand, hydrolases released from elements of invading capillary sprouts may also have a lyric effect on the matrix (7). In view of the two possibilities mentioned above, an acid protease isolated from bovine costal cartilage has been compared with an acid protease isolated from alveolar macrophages of rabbits as regards their effects on proteinpolysacch aride light component (PP-L)isolated from costal cartilages of calves (5) and on the proteoglycan subunit isolated from bovine nasal cartilage (6). Thin slices of fresh costal cartilage from calves were extracted two times at 4oC for 24 hours each time with 10 volumes of deionized water which was saturated with chloroform. After filtration through a sintered-glass filter, the filtrate was made 0.05 M in KC1 and 0.005 M in ~a~ttPO4. The pH of the solution was adjusted to 7.0 by the addition of concentrated HC1. To this solution at 20~ a 10 per cent solution of eetylpyridinium chloride in a 0.005 M sodium phosphate buffer, pit 7.0, which was also 0.05 M in KC], was slowly added with stirring until a floeeulent end point was reached. The resultant precipitate was removed by filtration through a sinteredglass filter of medium porosity. Thereafter the clear filtrate was set aside at 4oC overnight. If excess cetylpyridinium chloride precipitated during this time, it was removed by filtration at 4oC. The solution was dialyzed against a 0.005 M sodium phosphate buffer, pit 7.0, which was also 0.05 M in KC1, for 6 hours at room temperature and then against water saturated with chloroform for 16 hours. It was next equilibrated by dialysis against a 0.005 M potassium acetate buffer, pit 4.0, which was also 0.05 M in KCI. Of the resultant retent~te, 1000 ml were passed through a 2 x30 em column of SE-Sephadex C-25, which too had been previously equilibrated

Some Observations on the Isolation and Estimation of the Soluble Nucleotides of Wheat Seedlings

Extracts of germinating wheat seedlings contain substances which absorb ultraviolet light strongly but are not nucleotides. In particular, two glucosides seriously interfere with the isolation and estimation of soluble nucleotides and these compounds are not separated from the nucleotides by a charcoal adsorp tion procedure. A new extraction method is now described which avoids the use of charcoal. Freeze-dried tissue powders placed above a column of cellulose powder are extracted first with methanol/5 per cent, potassium acetate buffer pH 6-o (90:10), then absolute ethanol, and finally with 30 per cent, ethanol containing acetic acid (0 01 M). The effluent containing the nucleotides is sub jected either to dialysis or to ion-exchange resin absorption. During germina tion soluble nucleotides in the endosperm remain at a low level, but in the embryo there is a thirtyfold increase in z days. No evidence for the presence of a cytosine compound in the soluble nucleotide fraction of wheat embryos has been obtained. Guanine, adenine, and uridylic acid were the only detectable products of acid hydrolysis of the wheat seedling soluble nucleotides.