Cell-surface expression of H-2Db requires N-linked glycans

The question of whether beta-2 microglobulin (B2m)-independent expression of the mouse major histocompatibility complex (MHC) antigen H-2D^b results from the atypical glycosylation pattern associated with this MHC antigen (i. e., three glycans instead of two) has been addressed. Cell-surface expression of transfected H-2D^b in the B2m deficient cell line RIE was completely abolished by the drug tunicamycin (Tm). Introduction of a functional B2m gene by transfection did not re-establish cell-surface expression of D^b in the presence of Tm. Tm had no effect, however, on the expression of a truncated D^b molecule lacking the 1 and 2 domains which is glycosylated at amino acid position 256, suggesting that the D^b molecule, unlike other class I antigens, possesses an unstable conformation in the 1 and/or 2 domains which requires the attachment of glycans before it is transported to the cell surface. Once attached, however, glycans may confer a stable 1/2 conformation apparently peculiar to D^b which allows cell-surface expression in the absence of B2m.     

Polymorphism of human liver alcohol dehydrogenase: Identification of ADH2 2-1 and ADH2 2-2 phenotypes in the Japanese by isoelectric focusing

Liver homogenate-supernatants from most Japanese exhibit an atypical pH optimum for ethanol oxidation at pH 8.8 instead of 10.5, the typical pH-activity optimum. It has been proposed that atypical livers contain alcohol dehydrogenase isozymes with ₂ subunits while typical livers contain isozymes with ₁ subunits, both produced by the ADH ₂ gene. Because it is difficult to differentiate the atypical ADH₂ 2-2 phenotype from the ADH₂ 2-1 phenotype by starch gel electrophoresis, an agarose isoelectric focusing procedure was developed that clearly separated the atypical Japanese livers into two groups, A1 and A2. The isozymes in A1 and A2 livers were purified. Type A1 livers contained a single isozyme with an atypical pH-rate profile; it was designated ₂₂. Three isozymes were isolated from A2 livers, two of which corresponded to ₁₁ and ₂₂. A third, absent from the typical and the atypical A1 livers, had an intermediate mobility; it was designated ₂₁. Type A1 livers are, therefore, the homozygous ADH₂ 2-2 phenotype, and type A2 livers, the heterozygous ADH₂ 2-1 phenotype. The ADH₂ 2-2 phenotype was found in 53% of 194 Japanese livers, and the ADH₂ 2-1 phenotype, in 31%. Accordingly, the frequency of ADH ₂ ² was 0.68.This study was supported by U.S. Public Health Service Grant AA 02342.     

The Synthesis and Antiviral Activity of Glycyrrhizic Acid Conjugates with α-D-Glucosamine and Some Glycosylamines

Glycyrrhizic acid and its 30-methyl ester were conjugated with 2-amino-1,3,4,6-tetra-O-acetyl-2-deoxy--D-glucopyranose, 2,3,4,6-tetra-O-acetyl--D-glucopyranosyl amine, 2,3,4-tri-O-acetyl--L-arabinopyranosyl amine, 2-acetamido-2-deoxy--D-glucopyranosyl amine, and -D-galactopyranosyl amine using N,N-dicyclohexylcarbodiimide and its mixtures with N-hydroxybenzotriazole. Structures of the conjugates were confirmed by IR, UV, ¹H, and ¹³C NMR spectroscopy. The glycoconjugate with the residues of 2-acetamido-2-deoxy--D-glucopyranosyl amine in the carbohydrate part of its molecule exhibited antiviral activity (ID₅₀ 4 g/ml) toward the herpes simplex type 1 virus (HSV-1) in the VERO cell culture. Two compounds demonstrated anti-HIV-1 activity (50–70% inhibition of p24) in a culture of MT-4 cells at concentrations of 0.5–20 g/ml.     

Assembly-dependent expression of antigenic epitopes by β2-microglobulinb

In this report we provide evidence for the expression of antigenic epitopes on mouse (₂-microglobulin^b _2m ^b) that result from assembly with cognate H-2 class I heavy chains. For the cell line 69.9.15 (₂m^a × ₂m^b), which expresses a mutant cytosolic form of H-2K^b and wild-type H-2D^b, flow cytometry with rabbit antiserum against mouse ₂m displayed ₂m expression by cells grown in the presence or absence of fetal calf serum. By contrast, the epitopes identified by the ₂m^b-specific monoclonal antibody (mAb) S19.8 and clone 23 were not expressed by 69.9.15 cells grown in serum-containing conditions, and although S19.8 reactivity was weakly recovered by culture in the absence of serum, no such reacitivity was observed with clone 23. Strong expression of these epitopes was achieved following transfection of 69.9.15 cells with the wild-type H-2K ^b gene, indicating that the ₂m^b epitopes defined by mAb S19.8 and clone 23 were expressed when ₂m^b was assembled with an appropriate heavy chain. In support of this conclusion, we observed the recovery of the S19.8 and clone 23 epitopes by in vitro assembly of H-2K^b heavy chains with ₂m^b in the presence of the VSV N protein p52–59; however, such epitopes were expressed neither by ₂m^b prior to heterodimer assembly nor by non-conformed ₂m^b present in tissue culture supernatants recovered from H-2 class I surface positive cells. Taken together, these data indicate that in addition to the property of ₂m to modify the antigenicity of the MHC class I heavy chains, ₂m epitopes are induced in a reciprocal manner by assembly with MHC class I heavy chain molecules. Correspondence to: R. A. Zeff.     

Inoculation of sugar mill by-products compost with N2-fixing bacteria

Inoculation of sugar mill by-products compost with N₂-fixing bacteria may improve its quality by increasing total N and available P. Compost was inoculated with Azotobacter vinelandii(ATCC 478), Beijerinckia derxii (ATCC 49361), and Azospirillumsp. TS8, each alone and all three together. Numbers of all N₂-fixing bacteria in compost declined from an initial population of 5×10⁵cellsg^–1 during incubation. The population of Azotobacter declined to approximately 2×10²cellsg^–1 and the population of Beijerinckia and Azospirillum declined to approximately 9×10³ and 3.5×10⁴cellsg^–1 respectively, at day 50. Inoculation with N₂-fixing bacteria increased acetylene reduction, total N by 6–16 and available P by 25–30% in comparison to the uninoculated control. Increasing the N content and P availability of compost increases its value and there may be additional benefit from providing N₂ fixing bacteria.     

Holling's “hungry mantid” model for the invertebrate functional response considered as a Markov process. Part II: Negligible handling time

In this paper we analyse a stochastic model for invertebrate predation taking account of the predator's satiation. This model approximates Holling's hungry mantid model when handling time is negligible (see Part I). For this model we derive equations from which we can calculate the functional response and the variance of the total catch. Moreover we study a number of approximations which can be used to calculate these quantities in practical cases in a relatively simple manner.List of Notation a rate constant of digestion - b maximum of rate constant of prey encounter in the mantid - c satiation threshold for search - c satiation threshold for pursuit in the mantid - c _i (w^1/2(N- N)ⁱ) - expectation operator - f rate of change of satiation during search - F functional response: mean number of prey eaten per unit of time - g rate constant of prey capture - h probability generating function of N conditional on S = s times p - H probability generating function of N - m_i ¹ - n, N number of prey caught - p probability density of S - p_n simultaneous probability (density) of N and S - q probability of strike success - r dummy variable in generating function - s, S satiation - T _s search time - T _d digestion time - v asymptotic rate of increase of var v - V asymptotic rate of increase of var N - w weight of edible part of prey - W standard Wiener process - x prey density - z (N{S = s}-N)p - rate constant of prey escape time maximum pursuit time - (v{S = + w ^1/2}-v) - present time as a fraction of the time from the start to the end of the experiment - hazard rate of T _s - mean time between (downward) passages of S through c - v w_–1/2(N-) - edible prey biomass density - probability density of , number pi - parameter of Weibull distribution of T _s = (1/2acx(-g(c)))_1/2 - w_–1/2(S -) - satiation in the guzzler approximation: solution to d/dt = f() + g(), (0)=S(0). - biomass functional response: wF - total biomass catch in the guzzler approximation: solution to d/dt = g(), (0) = 0     

Identification of a GDP-Fuc:Galβ1–3GalNAc-R (Fuc to Gal)α1–2 fucosyltransferase and a GDP-Fuc:Galβ1–4GlcNAc (Fuc to GlcNAc)α1–3 fucosyltransferase in connective tissue of the snailLymnaea stagnalis

Connective tissue of the freshwater pulmonateLymnaea stagnalis was shown to contain fucosyltransferase activity capable of transferring fucose from GDP-Fuc in 1–2 linkage to terminal Gal of type 3 (Gal1–3GalNAc) acceptors, and in 1–3 linkage to GlcNAc of type 2 (Gal1–4GlcNAc) acceptors. The 1–2 fucosyltransferase was active with Gal1–3GalNAc1-OCH₂CH=CH₂ (K _m=12 mM,V _max=1.3 mU ml^–1) and Gal1–3GalNAc (K _m=20 mM,V _max=2.1 mU ml^–1), whereas the 1–3 fucosyltransferase was active with Gal1–4GlcNAc (K _m=23 mM,V _max=1.1 mU ml^–1). The products formed from Gal1–3GalNAc1-OCH₂CH=CH₂ and Gal1–4GlcNAc were purified by high performance liquid chromatography, and identified by 500 MHz¹H-NMR spectroscopy and methylation analysis to be Fuc1–2Gal1–3GalNAc1-OCH₂CH=CH₂ and Gal1–4(Fuc1–3)GlcNAc, respectively. Competition experiments suggest that the two fucosyltransferase activities are due to two distinct enzymes.Abbreviations 2Fuc-T 1–2 fucosyltransferase - 3Fuc-T 1–3 fucosyltransferase - MeO-3Man 3-O-methyl-D-mannose - MeO-3Gal 3-O-methyl-D-galactose     

Purification and characterization of two intracellular β-glucosidases from the Neurospora crassa mutant cell-1

Two intracellular -glucosidases (E.C. 3.2.1.21) were purified from the filamentous fungus Neurospora crassa, mutant cell-1 (FGSC no. 4335) and characterized. The extent of purification were 2.55- and 28.89-fold for -glucosidase A and -glucosidase B, respectively. -Glucosidase A was a dimeric protein, and B a monomeric protein, with molecular masses of 178 and 106 kDa, respectively. Both isoenzymes were glycoproteins with relatively high carbohydrate contents (-glucosidase A, 29.2%; -glucosidase B, 34.2%). The isoelectric points determined by IEF were 6.27 and 4.72, respectively. pH optima for activity were determined to be 5.0 and 5.5, and temperature optima to be 55 and 60 °C, for -glucosidases A and B, respectively. Both purified -glucosidases. especially -glucosidase B, showed relatively high stability against pH and temperature. Both enzymes were stable in the pH range of 5.0–9.0. The activities were completely retained up to 48 h at temperatures below 40 °C. At higher temperatures, enzymes were relatively unstable and lost their activities at 60 °C after 24 h. Both -glucosidases were highly activated by CuCl₂, and inhibited by SnCl₂ and KMnO₄. Hg²⁺ and Ag⁺ also inhibited severely -glucosidase B. The K _m and V _max values of the isoenzymes against cellobiose as substrate were 1.50 mM and 12.2mol min^–1 mg^–1 for -glucosidase A and 2.76 mM and 143.5 mol min^–1 mg^–1 for -glucosidase B.     

The expression of I-Ed molecules in F1 hybrid mice detected with antigen-specific,I-Ed-restricted cloned T-cell lines

The expression of polymorphic determinants on I-E molecules is largely dependent on allelic variation in the E chain. We have previously analyzed the expression of E ^k and E ^b chains in F₁ hybrid mice by a combination of techniques, and have shown that functional variation detected by the responsiveness of cloned T-cell lines specific for these molecules correlates well with serological determination of E expression. In the present study, we have extended our analysis to E ^d expression in F₁ hybrid mice. We show that E ^d is relatively poorly expressed in three F₁ combinations: H-2 ^d× H-2 ^b, H-2 ^d× H-2 ^s, and H-2 ^d× H-2 ^u. The former two crosses express E chains from the H-2 ^dparent only; when recombinant strains carrying E ^b or E ^s and an active E gene are used, E ^d expression is significantly increased. On the other hand, H-2 ^umice synthesize E chains; the poor expression of E ^d chains in this F₁ hybrid apparently reflects the strong preferential association of E ^u chains with all E molecules thus far analyzed. These results confirm that E chains compete for binding to E chains and that preferential association of different allelic forms of E chains with E chains is a generalized phenomenon. They also illustrate the importance of the rate of biosynthesis of Ia chains for cell-surface expression.     

Interspecies exchange of β 2-microglobulin and associated MHC and differentiation antigens

Radiolabeled human ₂-microglobulin (₂m) can bind to mouse histocompatibility (H-2) antigens on the cell surface or to partially purified H-2 antigens in solution. The complexes containing human ₂m and H-2 antigens from C3H (H-2^k) mice could be immunoprecipitated specifically with alloantisera, rabbit anti-H-2 xenoantisera, and with monoclonal H-2-specific antibodies. Specific association with H-2 antigens was also observed with other haplotypes. The only exception was B10.D2 (H-2 ^d ) from which complexes containing human ₂M could only be precipitated with anti-H-2 xenosera. Thus radiolabeled human ₂M can be used as a specific label for mouse H-2 antigens in precipitation and radioimmunoassays. The application of this finding extends to major histocompatibility complex antigens of other species, and to differentiation antigens with primary association with ₂m.Abbreviations used in this paper MHC major histocompatibility complex - ₂m ₂-microglobulin - LcH Lens culinaris hemagglutinin     

Antioxidants from carbon dioxide fixing Chlorella sorokiniana

Chlorella sorokiniana H-84, which has toleranceto high temperatures and high concentrations ofCO₂, has been isolated from a hot spring inJapan. Large-scale culturing of C. sorokinianawas carried out in air containing 10% CO₂.Analysis of the biomass shows that protein, carbohydrate and lipids comprised 68.5, 11.9 and10.0% of dry matter, respectively. The totalcarotenoids comprised 0.69% dry matter. The luteinand -carotene contents were 4300 and 600 gg^-1 dry weight, respectively. The-tocopherol content was 112 g g^-1 dry weight. These carotenoids and -tocopherolare known to possess radical scavenging activity.Two fractions with radical scavenging activity wereisolated from the aqueous extract of C.sorokiniana H-84. The extract showed several singlepeaks by reversed phase HPLC analysis and two of themhad molecular weights of 710 and 1286, respectively.     

Uncoupling and isotope effects in γ-butyrobetaine hydroxylation

Replacement of unlabeled -butyrobetaine with -[2,3,4-²H₆]butyrobetaine has a profound effect on the stoichiometry between decarboxylation of 2-oxoglutarate and hydroxylation in the reaction catalyzed by human -butyrobetaine hydroxylase. The ratios between decarboxylation and hydroxylation are 1.16 with Unlabeled and 7.48 with deuterated -butyrobetaine as substrate. From these ratios an internal isotope effect of 41 has been calculated. DV in the overall reaction measured as 2- oxoglutarate decarboxylation is 2.5 and D_V/K is 1.0. For -butyrobetaine hydroxylase fromPseudomonas sp. AK 1, 2-oxoglutarate decarboxylation exceeds hydroxylation with 10% when deuterated -butyrobetaine is used. No excess was found with unlabeled substrate and no internal isotope effect could be calculated. D_V for the bacterial enzyme is 6.     

Sequence divergence of B2m alleles of wild Mus musculus and Mus spretus implies positive selection

Mouse ₂-microglobulin (₂m) is polymorphic. Sequences of five allelic wild mouse B2m genes have been determined from the large exons of genomic DNA using the polymerase chain reaction. Relative to the standard B2m ^a allele, the products of four alleles of Mus musculus origin (w2, w3, w4, and w5), differ by only one or two amino acids. w5 has a single nucleotide change, Asp85 Val, and is identical to the c allele. w2 differs at Arg81 Thr and w4 at His34 Gln, and they share the Asp85 Val change with B2m ^c and B2m ^w5.w5 and c cells are lysed by S19.8, a monoclonal antibody specific for 2m^b (Ala85), in a complement-mediated cytotoxicity assay, whereas w4 cells are not. Thus, distant changes appear to introduce subtle conformational effects on 2m structure. Five independent isolates of Mus spretus (w1) differ the most from B2m ^a, with 12 amino acid changes and only one silent substitution. Replacements predicted from the nucleotide sequence occur in loops of the molecule facing away from the class I heavy chain and not in regions where 2m associates with class 1 3 domains. Concordantly, the w1 – 5 allelic forms of 2m associate well with H-2 heavy chains. The many amino acid changes in the spretus sequence and the paucity of silent substitutions suggest that B2m has been subject to positive selection.The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession numbers M84362-M84367 and L04992-L04994.     

Elevated CO2 effects on carbon and nitrogen cycling in grass/clover turves of a Psammaquent soil

Effects of elevated CO₂ (525 and 700 L L^–1), and a control (350 L L^–1 CO₂), on biochemical properties of a Mollic Psammaquent soil in a well-established pasture of C3 and C4 grasses and clover were investigated with continuously moist turves in growth chambers over four consecutive seasonal temperature regimes from spring to winter inclusive. After a further spring period, half of the turves under 350 and 700 L L^–1 were subjected to summer drying and were then re-wetted before a further autumn period; the remaining turves were kept continuously moist throughout these additional three consecutive seasons. The continuously moist turves were then pulse-labelled with ¹⁴C-CO₂ to follow C pathways in the plant/soil system during 35 days.Growth rates of herbage during the first four seasons averaged 4.6 g m^–2 day^–1 under 700 L L^–1 CO₂ and were about 10% higher than under the other two treatments. Below-ground net productivity at the end of these seasons averaged 465, 800 and 824 g m^–2 in the control, 525 and 700 L L^–1 treatments, respectively.in continuously moist soil, elevated CO₂ had no overall effects on total, extractable or microbial C and N, or invertase activity, but resulted in increased CO₂-C production from soil, and from added herbage during the initial stages of decomposition over 21 days; rates of root decomposition were unaffected. CO₂ produced h^–1 mg^–1 microbial C was about 10% higher in the 700 L L^–1 CO₂ treatment than in the other two treatments. Elevated CO₂ had no clearly defined effects on N availability, or on the net N mineralization of added herbage.In the labelling experiment, relatively more ¹⁴C in the plant/soil system occurred below ground under elevated CO₂, with enhanced turnover of ¹⁴C also being suggested.Drying increased levels of extractable C and organic-N, but decreased mineral-N concentrations; it had no effect on microbial C, but resulted in lowered microbial N in the control only. In soil that had been previously summer-dried, CO₂ production was again higher, but net N mineralization was lower, under elevated CO₂ than in the control after autumn pasture growth.Over the trial period of 422 days, elevated CO₂ generally appears to have had a greater effect on soil C turnover than on soil C pools in this pasture ecosystem.     

The multi-locus H-2D w16 region has an organization distinct from the D d region

Genomic DNA blot analyses using probes derived from the BALB/c 3 flanking region of the L ^d gene (L ^d 3 fl-C) and from near the BALB/c D3 ^d gene (50.2A) indicate that the B10.GAA37 mouse strain has a multi-locus D (D ^w16) region distinct from the five-gene organization observed in the D ^d and D ^q regions. To isolate the D ^w16 region class I genes, a genomic B10. GAA37-EMBL3 library was generated and screened with probes that preferentially hybridize to K and D region class I genes. Hybridization analyses of the isolated clones with L ^d derived oligonucleotide probes suggested that one of the clones contained the L ^w16 gene, whereas several other clones contained the L ^w16 gene. The sequence of the D ^w16 gene is most similar to that of the D ^p gene, particularly in the 3 half. Furthermore, the L ^w16 gene is quite similar in the 5 half and virtually identical in the 3 half to the L ^d gene, indicating that L ^w16, but not D ^w16, is a member of the L ^d gene family. Collectively, these data suggest that, through a D region recombination event, the novel D ^w16 region may have been assembled from primordial counterparts of the D ^p and L ^d genes.The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession number M60774-M60776, and M62759.     

Synthesis of Aminoethyl Glycosides of the Carbohydrate Chains of Glycolipids Gb3, Gb4, and Gb5

4-O-Glycosylation of 2-azidoethyl 2,3,6-tri-O-benzoyl-4-O-(2,3,6-tri-O-benzoyl--D-galactopyranosyl)--D-glucopyranoside with ethyl 2,3,4,6-tetra-O-benzyl- and ethyl 3-O-acetyl-2,4,6-tri-O-benzyl-1-thio--D-galactopyranoside in the presence of methyl trifluoromethanesulfonate led to trisaccharide 2-azidoethyl (2,3,4,6-tetra-O-benzyl--D-galactopyranosyl)-(14)-(2,3,6-tri-O-benzoyl--D-galactopyranosyl)-(14)-2,3,6-tri-O-benzoyl--D-glucopyranoside and its 3"-O-acetylated analogue, 2-azidoethyl (3-O-acetyl-2,4,6-tri-O-benzyl--D-galactopyranosyl)-(14)-(2,3,6-tri-O-benzoyl--D-galactopyranosyl)-(14)-2,3,6-tri-O-benzoyl--D-glucopyranoside in yields of 85 and 83%, respectively. Deacetylation of the latter compound and subsequent glycosylation with 4-trichloroacetamidophenyl 3,4,6-tri-O-acetyl-2-deoxy-1-thio-2-trichloroacetamido--D-galactopyranoside and 4-trichloroacetamidophenyl 4,6-di-O-acetyl-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl--D-galactopyranosyl)-1-thio-2-trichloroacetamido--D-galactopyranoside in dichloromethane in the presence of N-iodosuccinimide and trifluoromethanesulfonic acid resulted in the corresponding selectively protected derivatives of the tetrasaccharide GalNAc(13)Gl(14)Gal(14)Glc-OH₂CH₂N₃ and the pentasaccharide Gal(13)GalNAc(13)Gl(14)Gal(14)Glc-OH₂CH₂N₃ in 88 and 73% yields, respectively. Removal of O-protecting groups, substitution of acetyl group for the N-trichloroacetyl group, and reduction of the aglycone azide group resulted in the target 2-aminoethyl globo-tri-, -tetra-, and -pentasaccharide, respectively.     

Uptake ofpara-tyramine andmeta-tyramine into slices of the caudate nucleus and hypothalamus of the rat

The kinetics of the uptake ofp-tyramine,m-tyramine, and dopamine were investigated in slices of the hypothalamus and striatum of the rat in the presence of nialamide. When uptake was analyzed by a least-squares fit to a Lineweaver-Burk plot, each amine appeared to be concentrated by both a low-affinity and a high-affinity system in both brain regions. The obtainedK _m andV _max values for the high-affinity uptake system for each amine in both brain regions were similar. In general terms, the uptake systems in the striatum exhibited largerK _m andV _max values, with the velocity of uptake being in the order dopamine>m-tyramine>p-tyramine. 2,4-Dinitrophenol (DNP) and ouabain reduced all uptakes in the caudate, but reduced only the high-affinity uptake ofm-tyramine and the low-affinity uptake of dopamine in the hypothalamus.     

Biochemical documentation of allelic variation of the I-E antigens of the d,k, p,r, and u haplotypes

The extent of allelic variation of the E and E polypeptide chains of the I-E antigens from the H-2> ^d ,H-2 ^k , H-2 ^p , H-2 ^r , and H-2 ^u haplotypes is described. E and E chains were individually labeled with arginine or lysine and compared by tryptic peptide analysis. The results indicate minimum variability among the E polypeptides encoded by the d, k, p, and r haplotypes. However, the E ^u chain differed significantly from the other allelic E gene products. On the other hand, the E alleles demonstrated substantial variability with the E ^d being notably less similar to the other alleles than they are to each other. These findings are consistent with a number of observations regarding the serology and functions of the I-E antigens.Abbreviations MHC major histocompatibility complex - NMS normal mouse serum - NP-40 Nonidet P-40 - NTS 0.25% NP-40, 10 mM Tris-Cl, 0.15 M NaCl (pH 7.4) - SDS sodium dodecylsulfate - SDS-PAGE polyacrylamide gel electrophoresis in the presence of SDS     

State and time delay estimation of continuous microorganisms cultivation

A continuous fermentation model taking into account the culture memory is used for a state estimation design. The influence of the culture memory on the process dynamics is accounted for by a time delay parameter. The proposed procedure of on-line state estimation in the case when the delay has a constant value is based on the extended Kalman observer. The case when the delay parameter is evaluated on-line is also considered. An adaptive state and parameter algorithm on the base of the extended Kalman filter is proposed. The theoretical results are applied to continuous culture for growth of a strain of Saccharomyces cerevisiae.List of Symbols X, S mg/l Biomass concentration and substrate concentration respectively - S ⁰ mg/l Feed substrate concentration - Z mg/l Past substrate concentration - µ h^–1 Specific growth rate taking into account culture memory - h^–1 Specific consumption rate - h Time delay parameter denoting culture memory - D h^–1 Dilution rate - State variables vector - W _ij Gain coefficient for on-line state and parameter estimation - F Substrate feed rate vector - () Gain coefficient matrix - R Square symmetric Riccati matrix - K Matrix of coefficients - K(t) Delay kernel taking account of culture memory - Denote an estimation value The partial support by Bulgarian National Science Research Foundation under Grant SRTS 428/94 Modeling and Control of Fermentation Processes Taking the Memory Effect into Account is gratefully acknowledged.     

Single mid-chain GlcNAcβ1-6Galβ1-4R sequences of linear oligosaccharides are resistant to endo-β-galactosidase ofBacteroides fragilis

Endo--galactosidase (EC 3.2.1.103) ofBacteroides fragilis, at 250 mU ml^–1, did not cleave the internal galactosidic linkage of the linear radiolabelled trisaccharide GlcNAc1-6Gal1-4GlcNAc, or those of the tetrasaccharides Gal1-4GlcNAc1-6Gal1-4GlcNAc and Gal1-4GlcNAc1-6Gal1-4Glc. The isomeric glycans which contained the GlcNAc1-3Gal1-4GlcNAc/Glc sequence were readily cleaved.Abbreviations GlcNAc 2-acetamido-2-deoxy-d-glucose - Lact lactose - MT maltotriose - MTet maltotetraose - R _MTet chromatographic migration rate in relation to that of maltotetraose