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Nonlinear kinetics are commonly observed in the enzymatic hydrolysis of cellulose. This nonlinearity could be explained by any or all of the following three factors: enzyme inactivation, product inhibition, or substrate heterogeneity. In this study, four different approaches were applied to test the above hypotheses using two Thermomonospora fusca endocellulases, E2 and E5. The lack of stimulation of cellulase activity by beta-glucosidase rules out the possibility of product inhibition as a cause of the observed nonlinearity. The results from the other three approaches all provide strong evidence against enzyme inactivation and strong evidence for substrate heterogeneity as the cause of the nonlinear kinetics. The most direct evidence for substrate heterogeneity is that pretreatment of swollen cellulose with either E2cd or E5cd gave a product that was hydrolyzed at a much (3- to 4-fold) slower rate than untreated swollen cellulose even though the initial treatment degraded only 15-18% of the substrate. Furthermore, the activation energy of E2 catalyzed hydrolysis of swollen cellulose increased from 10 kcal/mol for the initial rate to 29 kcal/mol for hydrolysis after 24% digestion.

A thermophilic xylanase from Bacillus strain D3 suitable for use as a bleach booster in the paper pulping industry has been identified and characterized. The enzyme is suited to the high temperature and alkaline conditions needed for using xylanases in the pulp industry. The xylanase is stable at 60 degrees C and relatively stable at high temperatures, with a temperature optimum of 75 degrees C. The pH optimum is 6, but the enzyme is active over a broad pH range. The xylanase has been cloned and sequenced, and the crystal structure has been determined. The structure of Bacillus D3 xylanase reveals an unusual feature of surface aromatic residues, which form clusters or "sticky patches" between pairs of molecules. These "sticky patches" on the surface of the enzyme are responsible for the tendency of the protein to aggregate at high concentrations in the absence of reagents such as ethylene glycol. The formation of dimers and higher order polymers via these hydrophobic contacts may also contribute to the thermostability of this xylanase.

This article describes two cases in which the advantages of the ESEM have been exploited in unanticipated ways. First, we have found that etching occurs as the electron beam scans the surface of uncoated polymers in the ESEM. The surface topography caused by this etching, as seen in ESEM images, reflects the morphology of crystalline structures in the polymers. This technique has been valuable in the study of such textures in polymers. The second application is related to our use of the ESEM in support of research on the deinking of paper. In this effort we have learned that an unconventional contrast mechanism can be used during ESEM imaging to distinguish between inked and non-inked areas of newsprint. Under usual operating conditions, ESEM imaging does not distinguish between inked and non-inked areas. However, at relatively low sample chamber pressures the non-inked areas appear brighter than inked areas in ESEM images. © 1993 Wiley-Liss, Inc.

FDP aldolase has been purified and crystallized from the muscle of codfish. The specific activity of the codfish enzyme was found to be two-thirds that of rabbit muscle aldolase. Other catalytic properties, the molecular weight, and the carboxyl-terminal structure were similar to those of rabbit muscle aldolase. A tryptic peptide containing the Schiff base-forming lysine (1) has been isolated and its primary structure determined as: Ala-Leu-Ser-Asp-His-His-Val-Tyr-Leu-Gln-Gly-Thr-Leu-Leu-βGlys-Pro-Asn-Met-Val-Thr-Ala-Gly-His-Ser-CMCys-Ser-His-Lys. Extensive homology observed in this region of the aldolase molecules isolated from biologically divergent sources indicates the importance of this structure for catalysis of the aldolase reaction.

We report a novel biodegradable piezoelectric composite fabricated from paper and the piezoelectric salt, sodium potassium tartrate tetrahydrate (Rochelle salt, which we term PiezoSalt). The piezoelectric composite is non-toxic and is fabricated free of environmentally harmful solvents by impregnating PiezoSalt into a paper matrix through the crystallization of a concentrated PiezoSalt brine solution. The composite exhibits an effective piezoelectric constant between 3 and 25 pC N-1, dielectric constant of 7, mass density of 625 kg m(-3), and a Young's modulus between 7 and 8 GPa. When directly actuated, cm-scale cantilevers consisting of PiezoSalt paper produced clearly audible sound waves, illustrating one potential application. PiezoSalt paper composite provides a scalable, high throughput approach for biodegradable sensors and transducers with unsurpassed environmentally friendly processing. (C) 2016 Elsevier B.V. All rights reserved.

RECENTLY, it has been obvious that in most biological materials N-acetylsialic acid (N-acetyl-neuraminic acid) and N-glycolloylsialic acid occur together. By the introduction of a micromethod for the determination of glycollic acid, Klenk and Uhlenbruck1 have made possible the evaluation of the amount of N-glycolloylsialic acid in isolated sialic acids. In search of a more direct method, we tried partition chromatography, employing the solvent systems previously used for the separation of sialic acids but with unfavourable results2,3. As the pK a of sialic acids are low, about pH 2.7, it is necessary to use rather a strong acid in the solvents to prevent the dissociation of the carboxylic group. Of the different acids tried, only trichloracetic acid and hydrochloric acid were suitable. On crystallization of the sialic acids we had observed that N-glycolloylsialic acid was much more insoluble in alcohols than N-acetylsialic acid. Therefore, we tried mixtures of alcohols with the acids mentioned above. The best results were obtained with n-butanol/n-propanol/ 0.1 N hydrochloric acid (1:2:1, v/v). In this solvent the R F values were for N-acetylsialic acid 0.45, and for N-glycolloylsialic acid 0.34, on Whatman paper No. 1. The solvent system applied cannot be used for the separation of diacetylsialic acids and is unsuitable for the separation of free acids and the methyl esters of the sialic acids.