Sequential Photochemical and Microbial Degradation of Organic Molecules Bound to Humic Acid

We studied the effects of photochemical processes on the mineralization by soil microorganisms of [2-¹⁴C]glycine bound to soil humic acid. Microbial mineralization of these complexes in the dark increased inversely with the molecular weight of the complex molecules. Sunlight irradiation of glycine-humic acid complexes resulted in loss of absorbance in the UV range and an increase in the amount of ¹⁴C-labeled low-molecular-weight photoproducts and the rate and extent of mineralization. More than half of the radioactivity in the low-molecular-weight photoproducts appears to be associated with carboxylic acids. Microbial mineralization of the organic carbon increased with solar flux and was proportional to the loss of A₃₃₀. Mineralization was proportional to the percentage of the original complex that was converted to low-molecular-weight photoproducts. Only light at wavelengths below 380 nm had an effect on the molecular weight distribution of the products formed from the glycine-humic acid complexes and on the subsequent microbial mineralization. Our results indicate that photochemical processes generate low-molecular-weight, readily biodegradable molecules from high-molecular-weight complexes of glycine with humic acid.     

Purification of NADP-dependent glutamate dehydrogenase from Pseudomonas aeruginosa and immunochemical characterization of its in vivo inactivation

The ‘high ammonia pathway’ enzyme glutamate dehydrogenase (NADP⁺) is inactivated in cells of Pseudomonas aeruginosa when the stationary phase of growth in reached. Purified glutamate dehydrogenase (NADP⁺) appeared to be a protein composed of six identical subunits with a molecular weight of 54 000. With antibodies raised against purified enzyme it was found that glutamate dehydrogenase (NADP⁺) inactivation is accompanied by a parallel decrease in immunologically reactive material. This suggests that glutamate dehydrogenase (NADP⁺) inactivation is caused or followed by rapid proteolysis.     

Combined gas chromatography-chemical ionization mass spectrometry of sphingolipids. I. Glucosyl sphingosine,ceramides and cerebrosides of the spleen in Gaucher's disease

Trimethylsilylated glucosyl sphingosine, ceramides and glucocerebrosides were analysed by combined gas chromatography (GC)-chemical ionization (CI) mass spectrometry. Isobutane, methane and ammonia were used as reactant gases for chemical ionization. Essentially the same fragment ions were detected in the spectra with the different reactant gases.Purified glucocerebrosides isolated from the spleen of a patient with Gaucher's disease were clearly separated into their 8 molecular species by gas chromatography. Three other minor components were detected by spectrometry, and these 11 molecular species of glucocerebrosides from the spleen of the patient with Gaucher's disease have been analysed.The ceramides obtained by periodate oxidation and then alkaline reduction of the glucocerebrosides were also separated into 11 molecular species by GC-CI mass spectrometry.Molecular weight could be determined using the major fragment ion of m/e (M⁺?90) in the spectra of ceramides and cerebrosides. The chemical ionization method is useful for structural analyses and determination of the molecular species of sphingoglycolipids.     

Binding of heparin to antithrombin III: The use of dansyl and rhodamine labels

Low molecular weight heparin of low-anticoagulant activity and high molecular weight heparin of correspondingly high activity were prepared by chromatography on protamine-Sepharose; preparations subjected to limited N-desulfation (5–10% free amino groups) by solvolysis were labeled with 5-dimethylaminonaphthalene-1-sulfonyl chloride (dansyl chloride) or rhodamine B isothiocyanate (RITC). The fluorescent heparins retained approximately 50% of the original anticoagulant activities. Dansyl-heparin on binding to antithrombin III (ATIII) exhibited a 2.5-fold enhancement of dansyl fluorescence intensity. This effect could be prevented by excess unlabeled heparin. A 7900 molecular weight dansyl-heparin preparation bound to ATIII with a stoichiometry of close to 2:1 and with an apparent association constant for binding (K_a) of 4.9 × 10⁵, m^?1, whereas a 21,600 molecular weight fraction bound at 0.7:1 with the protein and with an apparent K_a = 7.9 × 10⁵, m^?1. When ATIII reacted with a mixture of low molecular weight dansyl-heparin and low molecular weight RITC-heparin, there was enhancement of RITC fluorescence emission when excited at the dansyl excitation maximum; this effect was not observed when either of the labeled heparin species was prepared from high molecular weight material. The results are consistent with the proposal that a single molecule of high molecular weight, high-activity heparin occupies two sites when it binds to ATIII, whereas low molecular weight, low-activity heparin binds to the two sites separately.     

Abundance and diversity based on amoA genes of ammonia-oxidizing archaea and bacteria in ten wastewater treatment systems

The abundance and diversity of amoA genes of ammonia-oxidizing archaea (AOA) and bacteria (AOB) were investigated in ten wastewater treatment systems (WTSs) by polymerase chain reaction (PCR), cloning, sequencing, and quantitative real-time PCR (qPCR). The ten WTSs included four full-scale municipal WTSs, three full-scale industrial WTSs, and three lab-scale WTSs. AOB were present in all the WTSs, whereas AOA were detected in nine WTSs. QPCR data showed that AOB amoA genes (4.625?×?10⁴–9.99?×?10⁹ copies g^?1 sludge) outnumbered AOA amoA genes (<limit of detection–1.90?×?10⁷ copies g^?1 sludge) in each WTS, indicating that AOB may play an important role than AOA in ammonia oxidization in WTSs. Interestingly, it was found that AOA and AOB coexisted with anaerobic ammonia oxidation (anammox) bacteria in three anammox WTSs with relatively higher abundance. In a full-scale industrial WTS where effluent ammonia was higher than influent ammonia, both AOA and AOB showed higher abundance. The phylogenetic analysis of AOB amoA genes showed that genera Nitrosomonas was the most dominant species in the ten WTSs; Nitrosomonas europaea cluster was the dominant major cluster, followed by Nitrosomonas-like cluster and Nitrosomonas oligotropha cluster; and AOB species showed higher diversity than AOA species. AOA were found to be affiliated with two major clusters: Nitrososphaera cluster and Nitrosopumilus cluster. Nitrososphaera cluster was the most dominant species in different samples and distributed worldwide.     

Active center and subunit structure of transaldolase from Candida utilis.

Crystalline transaldolase (type III) isolated from Candida utilis is composed of two identical subunits, as shown by the following lines of evidence. 1. Tryptic digestion of the performic acid oxidized enzyme yields the number of ninhydrin- and arginine-positive peptides expected for identical subunits. 2. All attempts to separate both subunits by molecular weight or charge differences have failed. 3. Cyanogen bromide cleavage and sodium dodecyl sulfate gel electrophoresis of S-carboxymethylated transaldolase revealed four distinct peptides designated C₂ to C₅ according to their decreasing molecular weight and one additional peak, C₁, in low yield, presumably an aggregate or partially degraded peptide.By chromatography on Sephadex G-100 the maleylated cyanogen bromide digest from ¹⁴C-labeled β-giyceryl-transaldolase could be separated into four peptide peaks which have been analyzed for their amino acid composition. The largest peptide C₂ with a molecular weight of 16,800 was identified as the active site containing fragment. The four fragments together account for all amino acid residues in the entire protein.From transaldolase (type I) containing four methionine residues three cyanogen bromide peptides could be identified. By addition of the individual peptides a molecular weight of 37,100 ± 3500 could be calculated, which is half the molecular weight of the native enzyme. From experimental data presented so far both isoenzymes of transaldolase can be regarded as “half-of-the-sites” enzymes.     

Differential contributions of ammonia oxidizers and nitrite oxidizers to nitrification in four paddy soils

Rice paddy fields are characterized by regular flooding and nitrogen fertilization, but the functional importance of aerobic ammonia oxidizers and nitrite oxidizers under unique agricultural management is poorly understood. In this study, we report the differential contributions of ammonia-oxidizing archaea (AOA), bacteria (AOB) and nitrite-oxidizing bacteria (NOB) to nitrification in four paddy soils from different geographic regions (Zi-Yang (ZY), Jiang-Du (JD), Lei-Zhou (LZ) and Jia-Xing (JX)) that are representative of the rice ecosystems in China. In urea-amended microcosms, nitrification activity varied greatly with 11.9, 9.46, 3.03 and 1.43 μg NO₃⁻-N g⁻¹ dry weight of soil per day in the ZY, JD, LZ and JX soils, respectively, over the course of a 56-day incubation period. Real-time quantitative PCR of amoA genes and pyrosequencing of 16S rRNA genes revealed significant increases in the AOA population to various extents, suggesting that their relative contributions to ammonia oxidation activity decreased from ZY to JD to LZ. The opposite trend was observed for AOB, and the JX soil stimulated only the AOB populations. DNA-based stable-isotope probing further demonstrated that active AOA numerically outcompeted their bacterial counterparts by 37.0-, 10.5- and 1.91-fold in ¹³C-DNA from ZY, JD and LZ soils, respectively, whereas AOB, but not AOA, were labeled in the JX soil during active nitrification. NOB were labeled to a much greater extent than AOA and AOB, and the addition of acetylene completely abolished the assimilation of ¹³CO₂ by nitrifying populations. Phylogenetic analysis suggested that archaeal ammonia oxidation was predominantly catalyzed by soil fosmid 29i4-related AOA within the soil group 1.1b lineage. Nitrosospira cluster 3-like AOB performed most bacterial ammonia oxidation in the ZY, LZ and JX soils, whereas the majority of the ¹³C-AOB in the JD soil was affiliated with the Nitrosomona communis lineage. The ¹³C-NOB was overwhelmingly dominated by Nitrospira rather than Nitrobacter. A significant correlation was observed between the active AOA/AOB ratio and the soil oxidation capacity, implying a greater advantage of AOA over AOB under microaerophilic conditions. These results suggest the important roles of soil physiochemical properties in determining the activities of ammonia oxidizers and nitrite oxidizers.     

Studies on some aspects of peroxidase from submaxillary gland

A peroxidase has been purified 25- to 30-fold over crude homogenate from goat submaxillary gland, which shows a single band of protein on polyacrylamide gel electrophoresis at four different pH values (4.6–10.0). A molecular weight (M_r) of approximately 2 × 10⁴ per heme binding site has been found. The molecular weight of the enzyme determined by Sephadex-gel filtration method, appeared to be 4 × 10⁴. The sedimentation pattern of the purified enzyme shows a symmetrical peak, although there was evidence of some small heterogenous material near the meniscus. The sedimentation coefficient of the enzyme (s^o 20^wat 0.4% of the enzyme concentration) was found to be 4.18, which indicates the molecular weight of the enzyme to be approximately 6 × 10⁴.     

Synthesis of RNA in isolated polytene nuclei from salivary gland cells of Chironomus thummi

The incorporation of [³H]UTP into RNA by isolated polytene salivary gland nuclei of Chironomus thummi was investigated under different incubation conditions; the labeled RNA fractions were characterized by electrophoresis. The results suggested that at two characteristic ionic conditions most of the RNA synthesized was the product of RNA polymerase I or RNA polymerase II as distinguished by their differential sensitivities to α-amanitin. Electrophoretical analysis of the RNA synthesized under conditions favouring polymerase I showed that this RNA population consisted mainly of four distinct molecular weight fractions within a range between 2.8 × 10⁴ and 2.5 × 10⁶. Under conditions favouring polymerase II two fractions were detected: one with a broad molecular weight distribution around 0.4 × 10⁶ containing considerable amounts of poly(A)-bearing RNA molecules, and a second with a peak at a molecular weight of 2.8 × 10⁴.     

Increased Arginine Biosynthesis during Phosphorus Deficiency : A Response to the Increased Ammonia Content of Leaves

The accumulation of arginine in leaves of four citrus rootstock cultivars during P deficiency has been demonstrated to be due to increased de novo synthesis rather than decreased catabolism or increased protein degradation (E Rabe, CJ Lovatt, 1984, Plant Physiol 76: 747-752). In this report, we provide evidence (a) that the increased activity of the arginine biosynthetic pathway observed for citrus rootstocks grown under P-deficient conditions for 7 months is due to an increase in the concentration of ammonia in leaves of P-deficient plants and (b) that ammonia accumulation and removal through arginine systhesis are early responses to phosphorus deficiency for both a woody perennial, rough lemon (Citrus limon), and an herbaceous annual, summer squash (Cucurbita pepo). Transferring 5-day-old squash plants to a phosphorus-deficient nutrient solution for only 10 days resulted in a 2-fold increase in the concentration of nitrate in the youngest fully expanded leaves (YFE). Concomitantly, the specific activity of nitrate reductase doubled and the ammonia content of P-deficient YFE leaves increased to a concentration significantly greater that of leaves from healthy control plants (P < 0.05). Consistent with increased availability of ammonia, the incorporation of NaH¹⁴CO₃ into arginine plus urea doubled during phosphorus deficiency and arginine accumulated. Despite the accumulation of nitrate and ammonia in YFE leaves during phosphorus deficiency, the total nitrogen content of these leaves was less than that of the healthy control plants. Similar results were obtained for rough lemon. Nitrate content of the YFE leaves increased 1.5- and 3.0-fold in plants deprived of phosphorus for 6 and 12 weeks, respectively. Ammonia content of the leaves increased as P deficiency progressed to 1.4 ± 0.08 mg (± se, n = 4) per gram dry weight, a level 1.8-fold greater than that of the P-sufficient control plants. During P deficiency de novo arginine biosynthesis in rough lemon increased 10-fold. Immersing the petiole of YFE leaves from P-sufficient squash and rough lemon plants in 50 millimolar NH₄⁺ for 3 hours resulted in the accumulation of ammonia in the leaves, and a 4-fold increase in the incorporation of NaH¹⁴CO₃ into arginine plus urea. Taken together, these results provide strong evidence that the accumulation of nitrate and ammonia in leaves is an early response of both woody and herbaceous plants to P deprivation. The data are consistent with the hypothesis that increased de novo arginine biosynthesis in leaves during P deficiency is in response to ammonia content of the leaves.     

The stabilizing influence of divalent ions and Na+ on the di-decameric structure of Yoldia limatula hemocyanin

The stabilizing influence of Ca²⁺, Mg²⁺, Ba²⁺ and Na⁺ on the di-decameric structure of the hemocyanin of the bivalve, Yoldia limatula has been investigated by light-scattering molecular weight measurements and by analytical ultracentrifugation. The molecular weight (M_w) data, examined as a function of decreasing divalent ion and sodium ion concentrations at pH 8.0 and at a constant hemocyanin concentration of 0.10 g·l⁻¹, show biphasic transition profiles, with a sharp initial decline in M_w as the concentration of the stabilizing cations is reduced. The analysis of the molecular weight data is best described in terms of the four-species, di-decamer-decamer-dimer-monomer scheme of association-dissociation equilibria. About 25 to 35 bound divalent ions and about 10 bound Na⁺ ions per half-molecule or decamer are required in order to account for the initial step of the observed transitions. The subsequent transitions representing the decamer to dimer and the dimer to nonomer steps of the reaction account for the additional binding of three to four and two to four cations per dimer and per monomer, respectively. The relatively large number of divalent ions per decamer suggests strong ionic stabilization of the decamer to decamer contacts within the parent di-decameric assembly of Yoldia hemocyanin. This is consistent with earlier observations showing relatively few hydrophobic groups at the decamer to decamer contact areas.     

Effect of Toxic Metals on Indigenous Soil β-Subgroup Proteobacterium Ammonia Oxidizer Community Structure and Protection against Toxicity by Inoculated Metal-Resistant Bacteria

Contamination of soils with toxic metals is a major problem on military, industrial, and mining sites worldwide. Of particular interest to the field of bioremediation is the selection of biological markers for the end point of remediation. In this microcosm study, we focus on the effect of addition of a mixture of toxic metals (cadmium, cobalt, cesium, and strontium as chlorides) to soil on the population structure and size of the ammonia oxidizers that are members of the beta subgroup of the Proteobacteria (β-subgroup ammonia oxidizers). In a parallel experiment, the soils were also treated by the addition of five strains of metal-resistant heterotrophic bacteria. Effects on nitrogen cycling were measured by monitoring the NH₃ and NH₄⁺ levels in soil samples. The gene encoding the α-subunit of ammonia monooxygenase (amoA) was selected as a functional molecular marker for the β-subgroup ammonia oxidizing bacteria. Community structure comparisons were performed with clone libraries of PCR-amplified fragments of amoA recovered from contaminated and control microcosms for 8 weeks. Analysis was performed by restriction digestion and sequence comparison. The abundance of ammonia oxidizers in these microcosms was also monitored by competitive PCR. All amoA gene fragments recovered grouped with sequences derived from cultured Nitrosospira. These comprised four novel sequence clusters and a single unique clone. Specific changes in the community structure of β-subgroup ammonia oxidizers were associated with the addition of metals. These changes were not seen in the presence of the inoculated metal-resistant bacteria. Neither treatment significantly altered the total number of β-subgroup ammonia-oxidizing cells per gram of soil compared to untreated controls. Following an initial decrease in concentration, ammonia began to accumulate in metal-treated soils toward the end of the experiment.     

Limited proteolysis of some egg surface components is an early event following fertilization of the sea urchin, Strongylocentrotus purpuratus.

The surface proteins of eggs from Stronglocentrotus purpuratus were labeled with ¹²⁵I by lactoperoxidase-catalyzed iodination. The eggs were examined after solubilization and disaggregation in sodium dodecyl sulphate (SDS) by electrophoresis on SDS-polyacrylamide slab-gels. Seventy-five percent of the label was found in material with a molecular weight greater than 130,000. About 5% of the radioactivity was excluded from the gels. Upon fertilization, embryos show a redistribution of the radioactively labeled species. There is a decrease in the amount of very high molecular weight material but an increase (35–40%) in material excluded from the gel. In addition, new radioactive bands of lower molecular weight are found. This change of distribution in the radioactive bands is blocked by inclusion of soybean trypsin inhibitor either before or immediately after fertilization, which completely inhibits the cortical granule protease. The disappearance of high molecular weight components is prevented by treatment of the eggs with procaine during fertilization, although the appearance of low molecular weight bands (approximately 20,000 and 30,000) is not completely blocked by procaine treatment. Parthenogenic activation of eggs by butyric acid or partial metabolic activation by ammonia each leads to changes in the egg surface proteins which are similar but not identical to those seen after fertilization. The data suggest that the labeling occurs on the vitelline membrane, plasma membrane and jelly layer. The possible significance of limited proteolysis in fertilization is discussed.     

Synthesis of linear,cyclic and polypeptides having the sequence -Asp-βAla-Gly-Ser-βAla-Gly-His-βAla-Gly- as catalysts in hydrolytic reactions

Boc-Asp-βAla-Gly-Ser-βAla-Gly-His-βAla-Gly-OEt, Boc-Asp-βAla-Gly-Ser-βAla-Gly-Ser-βAla-Gly-His-βAla-Gly-OH, cyclo(Asp-βAla-Gly-Ser-βAla-Gly-His-βAla-Gly) and poly(Asp-βAla-Gly-Ser-βAla-Gly-His-βAla-Gly) were synthesized as catalysts in hydrolytic reactions. Asp and Ser residues were protected with a benzyl group, but the His residue was not protected during the synthesis. The protected linear-nonapeptides were prepared by synthesis and subsequent fragment condensation of three kinds of tripeptide which have the sequences-Asp(OBzl)-βAla-Gly-,-Ser(Bzl)-βAla-Gly- and -His-βAla-Gly-, respectively. The protected cyclic-nonapeptide was obtained by cyclization of H-Asp(OBzl)-βAla-Gly-Ser(Bzl)-βAla-Gly-His-βAla-Gly-OH with DCC-HOBr and the subsequent purification by silica gel column chromatography. The protected poly-nonapeptide was prepared by polymerization of H-Asp(OBzl)-βAla-Gly-Ser(Bzl)-βAla-Gly-His-βAla-Gly-OH with DPPA. Deprotection was performed with catalytic hydrogenation for the protected linear- and cyclic-nonapeptides, and with methanesulphonic acid for the protected polynonapeptide, respectively, to give final products. Catalytic actions of the linear-, cyclic- and polypeptides for hydrolysis of p-nitrophenyl acetate are also reported briefly.     

Thermal resistance to photoreactivation of ultraviolet light induced mutations in the lacI gene of E. coli ung

Ultraviolet light (UV) induced mutations in the lacI gene of Escherichia coli are thought to be targeted by DNA photoproducts. A number of reports suggest that both cyclobutyl pyrimidine dimers and pyrimidine (6−4) pyrimidone photoproducts may be involved. To investigate the potential contribution of each of these DNA photoproducts to mutagenesis in the lacI gene, we held UV-irradiated cells at a temperature of 44°C for 75 min and then exposed them to photoreactivating light (PR). This protocol is expected to preferentially deaminate specifically those cytosines that are contained in cyclobutyl dimers and subsequently monomerize the dimers to yield uracils in the DNA. In a strain deficient for uracil-DNA glycosylase (Ung⁻), these uracils would not be removed and a G : C → A : T transition would result at the site of the dimer. This protocol resulted in the enhancement of amber nonsense mutations that result from transitions at potential cytosine-containing dimer sites. The enhanced mutation frequencies resulting from this procedure were used to estimate the probability of dimer formation at the individual sites. A comparison of the dimer distribution with the mutation frequencies following UV alone suggests that both cyclobutyl dimers and (6−4) photoproducts contribute to UV-mutagenesis in the lacI gene. In addition, we conclude that the frequency of mutation at any particular site not only reflects the occurrence of DNA damage, but also the action of metabolic processes that are responsible for DNA repair and mutagenesis.     

Molecular cloning and biochemical characterization of the first Na-channel α-type toxin peptide (Acra4) from Androctonus crassicauda scorpion venom

Due to the medical importance played in Turkey by stings of the scorpion Androctonus crassicauda, its venom has been studied with more attention. In this communication we report a new toxic peptide, named Acra4, because it is the fourth peptide completely characterized from venom of this scorpion. The peptide contains 64 amino acid residues stabilized by four disulfide bridges, with a molecular weight of 6937 Da. Purification of the lethal peptide was performed by three steps of high performance liquid chromatography (HPLC) separations, and the molecular weight was determined by mass spectrometry analysis and the full amino acid sequence was obtained by direct Edman degradation in conjunction with gene cloning. The LD₅₀ of Acra4 was 50.5 ng/20 g mouse body weight (95% confidence intervals from 48.8 to 52.2 ng/20 g mouse body weight). Additionally, from a sample of cDNA of A. crassicauda four genes were cloned displaying sequence similarities to known scorpion toxins, and are reported here as potentially toxic peptides, named Acra5 to Acra8. Electrophysiological studies of Acra4 were performed using Na⁺-channels expressed in F11 cell culture, by patch-clamp recordings. This is the first time that such peptide from A. crassicauda having a specific Na⁺-channel α-type effect is reported. Its affinity toward Na⁺-channels in F11 cell line is in the order of 1 μM concentration.     

Molecular and catalytic properties of the acetoacetyl-coenzyme A thiolase of Escherichia coli.

The acetoacetyl-CoA-thiolase, a product of the acetoacetate degradation operon (ato) was purified to homogeneity as judged by polyacrylamide-gel electrophoresis at pH 4.5, 7.0, and 8.3. The enzyme has a molecular weight of 166,000 and is composed of four identical subunits. The subunit molecular weight is 41,500. Histidine was the sole N-terminal amino acid detected by dansylation. The thiolase contains eight free sulhydryl residues and four intrachain disulfide bonds per mole. The ato thiolase catalyzes the CoA- dependent cleavage of acetoacetyl-CoA and the acetylation of acetyl-CoA to form acetoacetyl-CoA. The maximal velocity in the direction of acetoacetyl-CoA cleavage was 840 nmol min^? (enzyme unit)^?1 and the maximal velocity in the direction of acetoacetyl CoA formation was 38 nmol min^?1 (enzyme unit)^?1. Like other thiolases, the ato thiolase was inactivated by sulfhydryl reagents. The enzyme was protected from inactivation by sulfhydryl reagents in the presence of the acyl-CoA substrates, acetyl-CoA and acetoacetyl-CoA; however, no protection was obtained when the enzyme was incubated with the acetyl-CoA analog, acetylaminodesthio-CoA. Consistent with these results was the demonstration of an acetyl-enzyme compound when the thiolase was incubated with [1-¹⁴C]acetyl-CoA. The sensitivity of the acetyl-enzyme bond to borohydride reduction and the protection afforded by acyl-CoA substrates against enzyme inactivation by sulfhydryl reagents indicated that acetyl groups are bound to the enzyme by a thiolester bond.     

Control of molecular weight of poly-β-hydroxybutyric acid produced in fet-batch culture of Protomonas extorquens

Summary To control molecular weight of poly--hydroxybutyric acid (PHB) produced in a fedbatch culture of Protomonas extorquens, the effects of cultural temperature, pH, molar ratio of methanol and ammonia, and concentration of methanol in the medium on polymerization were inverstigated. Change of methanol concentration affected average molecular weight of PHB. When the cultivation was carried out at 0.05 g/l of methanol, average molecular weight of PHB reached above 8×10⁵. On the other hand, in the case of 32 g/l of methanol average molecular weight of PHB was less than 0.5×10⁵. Although every sample had a wide molelcular weight distribution, it became possible to control voluntarily average molecular weight of PHB.     

Actin and Myosin in pea tendrils

We demonstrate here the presence of actin and myosin in pea (Pisum sativum L.) tendrils. The molecular weight of tendril actin is 43,000, the same as rabbit skeletal muscle actin. The native molecular weight of tendril myosin is about 440,000. Tendril myosin is composed of two heavy chains of molecular weight approximately 165,000 and four (two pairs) light chains of 17,000 and 15,000. At high ionic strength, the ATPase activity of pea tendril myosin is activated by K⁺-EDTA and Ca²⁺ and is inhibited by Mg²⁺. At low ionic strength, the Mg²⁺-ATPase activity of pea tendril myosin is activated by rabbit skeletal muscle F-actin. Superprecipitation occurred after incubation at room temperature when ATP was added to the crude actomyosin extract. It is suggested that the interaction of actin and myosin may play a role in the coiling movement of pea tendril.