Immobilization of formaldehyde dehydrogenase in tailored siliceous mesostructured cellular foams and evaluation of its activity for conversion of formate to formaldehyde
COLLOIDS AND SURFACES B-BIOINTERFACES
Authors: Gomes, Milene Zezzi do Valle; Palmqvist, Anders E. C.
Abstract
Formaldehyde dehydrogenase (FaldDH) is used as a catalyst to reduce formate to formaldehyde in a cascade reaction to convert CO2 to methanol. This enzyme, however, has low activity and is sensitive to substrate/product concentration and pH. To improve the performance of FaldDH, it can be immobilized through physical adsorption in siliceous mesostructured cellular foams (MCF), which physical properties are suitable for the immobilization of large molecules as FaldDH (molecular size of 8.6 x 8.6 x 19 nm). In this work two MCF materials were synthesized: MCF1 with a pore size of 26.8 nm and window size of 10.5 nm; and MCF2 with a pore size of 32.9 nm and window size of 13.0 nm. The surfaces of the materials were functionalized with octyl, mercaptopropyl or chloromethyl groups. FaldDH was successfully immobilized inside all the materials, yielding enzyme loadings of about 300 mg g(-1) in MCF1 and more than 750 mg g(-1) in MCF2. However, the enzyme was inactive upon immobilization on MCF1, whereas on MCF2 the enzyme retained its catalytic activity presumably owing to the larger pores of this material and the need for the enzyme to undergo configurational changes during the reaction. Using MCF2 functionalized with mercaptopropyl groups the activity of FaldDH was enhanced beyond that of the free enzyme. Additionally, low leakage of the enzyme from the MCF2 was observed during the reactions. Thus, tailored MCF is a highly attractive material for employment of the FaldDH enzyme. (C) 2017 Published by Elsevier B.V.
GENE-MAPPING STUDIES CONFIRM THE HOMOLOGY BETWEEN THE PLATYPUS-X AND ECHIDNA X(1)-CHROMOSOMES AND IDENTIFY A CONSERVED ANCESTRAL MONOTREME X-CHROMOSOME
CHROMOSOMA
Authors: WATSON, JM; RIGGS, A; GRAVES, JAM
Abstract
The identification of the sex chromosomes in the three extant species of Prototherian mammals (the monotremes) is complicated by their involvement in a multivalent translocation chain at the first division of male meiosis. The platypus X chromosome, identified by the presence of two copies in females and one in males, has been found to possess a suite of genes that have been mapped to the X chromosomes of all eutherian and metatherian mammals. We have extended gene mapping studies to a member of the only other extant monotreme family, the echidna, which has a G-band equivalent X1 chromosome, as well as a smaller X2. We find that the five human X-linked genes (G6PD, GDX, F9, AR and MCF2) map to the echidna X1 chromosome in locations equivalent to those on the platypus X. These results confirm that the echidna X1 is the original X chromosome in this species, and identify a conserved ancestral monotreme X chromosome.