Subunit structure and immunological properties of wheat carboxypeptidase

Wheat carboxypeptidases I, II, III and IV from wheat seeds with isoelectric points of 4.8, 5.6, 6.0 and 6.5, respectively, were found to be homogeneous by the Ouchterlony double immunodiffusion technique using an antiserum of the enzyme III. In a previous paper [1], the native enzyme III (MW = 118 k) was separated into two 58 k subunits (MW = 58 k) and further divided into the 35 k and 25 k fragments (MW = 35 k and 25 k, respectively). The native enzyme III and the 58 k subunit produced a single precipitin line against the antiserum. The 35 k and 25 k fragments did not cross-react with the antiserum. The amino acid compositions of the 35 k and 25 k fragments were similar to each other. Amino-terminal amino acids of the 35 k and 25 k fragments were both glutamic acid. Carboxy-terminal groups of the 35k and 25k fragments were determined to be -(Gly, Ser)-Glu-OH and -Thr-Pro-Glu-OH, respectively. The Ouchterlony double immunodiffusion technique revealed the presence of a common antigen in a carboxypeptidase from wheat seeds and one from germinated wheat. Comparison of both enzymes is discussed.     

Fractionation of K-562 cells on the basis of their surface properties by partitioning in two-polymer aqueous-phase systems

The K-562 cell line is a culture of human leukemia stem cells originally derived from a patient with chronic myelogenous leukemia in blast crisis. We have subjected such cells, in the log phase of growth, to countercurrent distribution in a charge-sensitive dextran-polyethylene glycol aqueous-phase system, a method that fractionates cells on the basis of subtle differences in their surface properties, and found that: (1) The cell population is heterogeneous since it is composed of cells with different partition ratios. (2) There is a correlation between increasing cell partition ratios and increasing cell electrophoretic mobilities. (3) Cells under different parts of the distribution curve have dissimilar ratios of cells in different parts of the cell cycle, a phenomenon that may, at least partially, be the basis for the subfractionation of these cells. There is a clear tendency for cells in G₀+G₁+early S to decrease and for those in late S+G₂+M to increase with increasing partition ratios. (4) Sialic acid is a major surface charge component of the cells as evidenced by a dramatic drop in their partition ratios after treatment with neuraminidase.     

The polarized UV-absorption spectra and the crystal structure of two different monoclinic crystal forms of the retinal homologue β-8′-apocarotenal

During the visual process, light absorption in the 11-cis retinylidene chromophore leads to a rapid cis-trans-isomerization which initiates the phototransduction step. Important spectroscopic properties of this chromophore can be derived from polarized UV-absorption spectra of crystalline 11-cis-retinal if a parallel X-ray structure analysis is performed. Several questions about the relation between molecular geometry and spectroscopic behavior could not be answered from these spectra. All crystal forms of 11-cis-retinal contain this molecule in its 6-s-cis-ring conformation. For the retinal homologue, -8-apocarotenal (APC), however, two crystal forms with different ring conformation can be grown. The spectrum of -APC (6-s-cis) shows a vibronic structure whereas that of -APC (6-s-trans) is diffuse but has a distinct shoulder on the low energy side of the main band. This S-band is typical for retinal spectra and has been ascribed to a transition into a ¹A _g ^-* -state. The appearance of the S-band is not correlated with a 6-s-cis-conformation as suggested by the retinal spectra but is due to intermolecular interactions: -APC has a dense dimer packing and a strong electrostatic interaction between the -electron systems. This might cause the forbidden ¹A _g ^-* -transition. On the other hand, this interaction is missing in the loose and polar packing of -APC which favors vibration in the polyene chain. This finding is remarkable in view of the photodynamic behavior of the visual chromophore for which strong electrostatic interactions with the protein helices of its binding site have to be postulated.Abbreviations APC 8--Apocarotenal - -APC/-APC /-form of crystallized APC - -CIS/-CIS /-form of crystallized 11-cis-retinal - ATR all-trans retinal - UV ultraviolet light - CI quantum-mechanical calculation employing configuration interaction - PPP-MRD quantum-mechanical calculations after Pariser, Parr, Pople employing multireference determinants - S-bands shoulder on main absorption band - R, S right, left enantiomer - EtOH ethyl alcohol - PE petroleum ether - E direction of electric vector of incident light - b crystallographic b-axis     

热带速生耐旱树种榆绿木的研究

榆绿木(Anogeissus acuminata var.lanceolata)在我国为一新纪录种,发现于云南省思茅县小橄榄坝为中心的狭窄河谷地带。本文对榆绿木的生态习性、生长特性和自然更新状况作了详细的分析,并对其材质和材性进行测定。榆绿木的气干容重为0.896 g/cm~3;顺纹抗压和抗弯强度之和高达1775 kg f/cm~2;静曲弹性模量203000 kg f/cm~2;冲击韧性达1.385kq f. m/Cm~2,是具有高强度、高韧性的工业用材。可作建筑、车辆、农具、体育运动器材及军工等用材。速生、耐旱,是一种有前途的干热河谷造林树种,还可作鞣料林和能源薪炭林栽培,具有很高的生态和经济价值。本文还对这一树种目前所面临的威胁作了分析,为合理开发利用及保护榆绿木森林资源提出了建议。     

Enzymatic isolation of living embryo sacs of Petunia

Summary A 20%–25% yield of isolated and living embryo sacs of Petunia hybrida L. was obtained using an enzymatic maceration mixture containing 3% driselase (soluble fraction only), 0.1% MES buffer, pH 5.5, and 8% mannitol. For each maceration ± 450 ovules were incubated in 1 ml enzyme solution for 2 h at 30° C in a shaking waterbath (150 rpm). Subsequently, the enzyme solution was replaced by Brewbaker and Kwack's medium, pH 6.5, supplemented with 10% mannitol (BKM). Gentle agitation of the suspension resulted in the liberation of embryo sacs, which were then collected with a micropipette using a dissecting microscope and transferred to fresh BKM. The embryo sacs isolated are intact and living, and have maintained their original shape and organization When stored in BKM at room temperature the isolated embryo sacs remain alive for 8 h. Storage at 4° C results in a prolongation of viability of up to 80 h. Prolonged incubation of ovules or reincubation of isolated embryo sacs in the maceration mixture results in the liberation of the gametophytic cells as individual, living protoplasts.     

Purification and properties of the carbonic anhydrase of Rhodospirillum rubrum

The carbonic anhydrase (EC 4.2.1.1) of Rhodospirillum rubrum has been purified to apparent homogeneity and some of its properties have been determined. The enzyme was cytoplasmic and was found only in photosynthetically grown cells. It had a molecular weight of about 28,000, and was apparently composed of two equal subunits. The amino acid composition was similar to that of other reported carbonic anhydrases except that the R. rubrum enzyme contained no arginine. The isoelectric point of the enzyme was 6.2 and the pH optimum was 7.5. It required Zn(II) for stability and enzymatic activity. The K _m(CO₂) was 80 mM. Typical carbonic anhydrase inhibition patterns were found with the R. rubrum enzyme. Strong acetazolamide and sulfanilamide inhibition confirmed the importance of Zn(II) for enzymatic activity as did the anionic inhibitors iodide, and azide. Other inhibitors indicated that histidine, sulfhydryl, lysine and serine residues were important for enzymatic activity.Abbreviation CA carbonic anhydrase In memory of R. Y. Stanier     

In situ behaviour of D(-)-lactate dehydrogenase from Escherichia coli

Some kinetic properties of the D(-)-lactate dehydrogenase (EC 1.1.1.28) of Escherichia coli have been investigated. There were marked differences between the kinetic properties of the enzyme studied in situ compared with the in vitro D(-)-lactate dehydrogenase. D(-)-Lactate dehydrogenase in situ showed high substrate inhibition with pyruvate over the pH range 6.0–7.0, whereas the enzyme in vitro did not. The pH optimum for pyruvate reduction by the in situ D(-)-lactate dehydrogenase ranged between pH 7.5 and 7.8, whereas the in vitro enzyme showed its pH optimum between pH 6.8 and 7.0. The pK values of the prototropic groups that controlled the enzymatic activity shift to the acidic region for the in vitro enzyme with respect to the in situ enzyme. In vitro D(-)-lactate dehydrogenase exhibits homotropic interactions with its substrate, pyruvate and its coenzyme, NADH, at pH values ranging between pH 6.0 and 8.5, but the in situ enzyme showed homotropic interactions neither with pyruvate nor with NADH at all pH values studied.     

Perspectives of data analysis of enzyme inhibition and activation,Part 1: Use of the three‐dimensional Km′ V′I coordinate system for data analysis of enzyme inhibition and activation

The possibility of construction of the three‐dimensional (unfolded and folded) K_m′ V′I rectangular coordinate systems convenient for vector representation of inhibited and activated enzymatic reactions as well as of a two‐dimensional K_m′ V′ scalar rectangular coordinate system convenient for diagrammatic representation of enzymatic reactions is considered. The perspectives of using the properties of the three‐dimensional L vectors and their scalar L projections for data analysis of enzyme inhibition and activation are analyzed. © 2009 Wiley Periodicals, Inc. J Biochem Mol Toxicol 23:97–100, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jbt.20273     

Development of Sphagnum fallax diaspores on bare peat with implications for the restoration of cut-over bogs

1. The growth of Sphagnum fallax was studied in a glasshouse experiment. Capitulum diaspores of S. fallax were cultivated on five different types of bare peat core, representing a gradient of increasing disturbance. Increases in length and weight were measured. Three microclimates were simulated by protecting the bare peat with a shading mesh and a plastic cover in combination with two water levels.
2. Significant differences in the growth of S. fallax were observed in relation to microclimate changes. Protection techniques such as shading mesh and perforated plastic film allowed a better development of the diaspores compared to bare peat. A plastic cover caused the best growth and compensated for a low water table level.
3. Peat properties are critical when diaspores grow in direct contact with decomposed peat. The porosity, and especially its vertical pattern in the peat profile, proved to be an important factor. A particular combination of microclimate conditions at the surface of the bare peat, and physical properties of the upper peat layers, may favour the growth of S. fallax diaspores even where there is a low water
Table 4 . Restoration of Sphagnum species on cut-over bogs needs to consider both the microclimate conditions at the surface of the bare peat and the peat properties themselves. These factors are important for the diaspores, particularly in periods of climatic and hydrological stress. In such situations, commensalism with some vascular plants may be a useful trigger for Sphagnum growth.     

Field Scale Variations in Soil Properties for Spatially Variable Control: A Review

This article reviews the widely scattered information on spatial variability of field-scale properties. It mainly addresses the variations in properties that influence nitrate accumulation and movement resulting from the agricultural activities in the root zone. The drive for this research comes from the perception and evidence of widespread contamination arising from production agriculture. The information is useful in the spatial management of soil for prevention of non-point source groundwater contamination from production practices. The review includes most of the static soil properties, one water transport property, some soil fertility variables, and crop yield. It examines various investigations and parameters identifying the magnitude of variability, and spatial correlation values for a given property are provided in a tabular form. Various sources of spatial variability, as well as methods of evaluating soil variability, are also discussed. For static soil properties, the range of coefficient of variation (CV) value was found to be small given the diversity of soils and field sizes on which the observations were conducted. The selected soil fertility variables and crop yield exhibited intermediate variations. However, CVs were considerably higher for the investigated transport property than those of static soil properties. The static soil properties and fertility variables were found to be correlated over a much larger distance than the transport property. If there was no variability, production through traditional practice with proper adjustment for field conditions would be the most appropriate choice. However, variations in soil and crop growth properties have led to attempts to understand these variations and application of spatially variable control in production agriculture.