Comparison of Extracellular Cellulase Activities of Clostridium thermocellum LQRI and Trichoderma reesei QM9414

The crude extracellular cellulase of Clostridium thermocellum LQRI (virgin strain) was very active and solubilized microcrystalline cellulose at one-half the rate observed for the extracellular cellulase of Trichoderma reesei QM9414 (mutant strain). C. thermocellum cellulase activity differed considerably from that of T. reesei as follows: higher endoglucanase/exoglucanase activity ratio; absence of extracellular cellobiase or β-xylosidase activity; long-chain oligosaccharides instead of short-chain oligosaccharides as initial (15-min) hydrolytic products on microcrystalline cellulose; mainly cellobiose or xylobiose as long-term (24-h) hydrolysis products of Avicel and MN300 or xylan; and high activity and stability at 60 to 70°C. Under optimized reaction conditions, the kinetic properties (V_max, 0.4 μmol/min per mg of protein; energy of activation, 33 kJ; temperature coefficient, 1.8) of C. thermocellum cellulose-solubilizing activity were comparable to those reported for T. reesei, except that the dyed Avicel concentration at half-maximal velocity was twofold higher (182 μM). The cellulose-solubilizing activity of the two crude cellulases differed considerably in response to various enzyme inhibitors. Most notably, Ag²⁺ and Hg²⁺ effectively inhibited C. thermocellum but not T. reesei cellulase at <20 μM, whereas Ca²⁺, Mg²⁺, and Mn²⁺ inhibited T. reesei but not C. thermocellum cellulase at >10 mM. Both enzymes were inhibited by Cu²⁺ (>20 mM), Zn²⁺ (>1.0 mM), and ethylene glycol-bis(β-aminoethyl ether)- N,N-tetraacetic acid (>10 mM). T. reesei but not C. thermocellum cellulose-solubilizing activity was 20% inhibited by glucose (73 mM) and cellobiose (29 mM). Both cellulases preferentially cleaved the internal glycosidic bonds of cellooligosaccharides. The overall rates of cellooligosaccharide degradation were higher for T. reesei than for C. thermocellum cellulase, except that the rates of conversion of cellohexaose to cellotriose were equivalent.     

Extracellular siderophores of rapidly growing Aspergillus nidulans and Penicillium chrysogenum

The highly active extracellular siderophores previously detected in young cultures of Aspergillus nidulans and Penicillium chrysogenum have been identified as the cyclic ester fusigen (fusarinine C), and its open-chain form, fusigen B (fusarinine B).     

D-propranolol and DL-propranolol both decrease conversion of L-thyroxine to L-triiodothyronine.

The effects of propranolol (DL-propranolol) and D-propranolol on thyroid hormone metabolism were studied in six euthyroid volunteers receiving L-thyroxine (T4) and six hypothyroid patients receiving T4 replacement. D-propranolol as well as propranolol decreased L-triiodothyronine (T3) concentrations and the ratio of T3 to T4 in the euthyroid subjects, and D-propranolol decreased these variables in the subjects with hypothyroidism (propranolol was not given to this group). It is concluded from this study and from parallel invitro investigations that the effect of propranolol on the conversion of T4 to T3 is unrelated to its beta-adrenergic blocking activity, and that at low therapeutic doses propranolol may exert appreciable "membrane-stabilising" effects in vivo.     

Miniature two-dimensional thin-layer chromatographic separation of lecithin and sphingomyelin

A miniature two-dimensional thin-layer chromatographic procedure employing silica gel impregnated glass-microfiber chromatography sheets (commercial product, ITLC-type SG sheets) has been developed for the separation of lecithin (L) and sphingomyelin (S) from a standard lipid mixture containing L, S, lysolecithin, phosphatidyl inositol (PI), phosphatidyl serine (PS), phosphatidyl ethanolamine, phosphatidyl glycerol, and diphosphatidyl glycerol. The newly developed procedure eliminates possible interference from PI and PS. Complete separation of L and S was easily achieved with chromatographic solvent migration times of approximately 3 and 2 min for the first and second dimensions, respectively. The lipids were visualized by charring and fluorescent staining techniques. The procedure has been adapted for the separation of L and S from amniotic fluid samples.     

Chemical modifications of actin: effects on interaction with deoxyribonuclease I

Maleylation of lysine residues, nitration of tyrosine residues or modification with 2,3-butanedione or 1,2-cyclohexanedione of arginine residues on actin resulted in a loss of polymerizability of the modified actin. However, only lysine modification produced a complete loss of the deoxyribunuclease I inhibitory ability of actin at low degrees of modification. By the level of one modified lysine per actin monomer, the samples completely lost polymerizability and lost 65% of their inhibitory power against deoxyribonuclease I-catalysed hydrolysis of DNA. By two lysines modified per actin, all inhibitory activity was lost. One lysine residue on actin apparently overlaps both an actin action contact site and an actin-deoxyribnuclease 1 contact site, offering a suggestion as to how deoxyribonuclease I blocks actin polymerization.     

Urinary excretion of a novel hexasaccharide and glycopeptide analogue in fucosidosis.

Repeated Biogel P6 chromatography of the urine from a patient with fucosidosis yielded several fractions containing fucosyloligosaccharides and glycopeptides. Two of these were shown by ¹H nuclear magnetic resonance (¹H-n.m.r.) spectroscopy and permethylation analysis to have the following structures respectively: (I) αfuc (1→3) [βgal (1→4)] βglcNAc (1→2) αman ($\text{1→}\text{3}\text{6}$) βman (1→4) glcNAc and (II) αfuc (1→3) [βgal (1→4)] βglcNAc (1→2) αman ($\text{1→}\text{3}\text{6}$) βman (1→4) βglcNAc (1→4) [αfuc ($\text{1→}\text{3}\text{6}$)] βglcNAc-Asn.     

A spectrofluorimetric investigation of calf thymus DNA modified by BP diolepoxide and 1-pyrenyloxirane

7β,8α-Dihydroxy-9α,10α-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BP diolepoxide, $\text{1}$) and 1-pyrenyloxirane ($\text{2}$) bind chemically to calf thymus DNA. The fluorescence efficiency of pyrenyl groups in mutagen modified DNA varies appreciably with its conformation and decreases in the order: pyrenees, modified denatured DNA and modified native DNA. A particularly interesting observation is that the fluorescence efficiency of mutagen modified DNA intensifies substantially upon denaturation. Our results suggest that the pyrenyl groups in mutagen modified DNA are intercalated between the base pairs of DNA. Since both $\text{1}$ and $\text{2}$ are powerful frame-shifting mutagens for S. typhimurium TA-98, the intercalative covalent binding of these compounds to DNA may provide a molecular basis for their mutagenic activity.     

Halogenated monoterpenes of the red alga Microcladia

The red marine algae Microcladia borealis, M. californica and M. coulteri produce several unusual halogenated monoterpenes including violacene, plocamene-B, plocamene-C, and plocamane-D. The isolation of these terpenes along with a study of their variation in each Microcladia at different locations are described.     

Death of Staphylococcus aureus in Liquid Whole Egg Near pH 8

Incubating and shaking Staphylococcus aureus in liquid whole egg causes a decline in viability. During the period of agitation, the natural pH of the egg rises from about 7.2 to between 8.0 and 8.2 as a result of a loss of carbon dioxide. However, if the pH of the egg is prevented from rising, either by not shaking or by addition of a buffer, S. aureus will grow. The cause of death is traced to the presence of lysozyme of egg white. Interestingly, the action of lysozyme is not attributable to its bacterial lytic property but, instead, to the basicity of the lysozyme molecule. This conclusion is supported by the fact that the lytic property of lysozyme is known to have its optimal activity near neutrality and by the finding that protamine sulfate, a nonenzymatic basic polypeptide, also caused death of S. aureus at pH 8.0 but not at 7.0. It was postulated that the rise in pH renders the bacterial cells more negatively charged, so that in the presence of positively charged molecules like lysozyme or protamine sulfate a complex is formed, agglutinating the cells.