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Upton, NY, United States

Gang O.,Brookhaven National Laboratory
Nature Materials | Year: 2012

Oleg Gang states that colloidal particles interacting through DNA linkers can be designed to form solids that melt when either heated or cooled. This scenario widens the temperature window in which colloidal superlattices form by reducing kinetic problems. One highly attractive aspect of DNA-based particle assembly is the ability to separate functional and structural requirements. The latest advancements have demonstrated more sophisticated constructs, such as DNA shells with tunable interactions, realized by varying the composition of two DNA strands on the shell and shells that can change structure and interactions through the incorporation of switchable and self-protected DNA strands. The bonding scheme proposed by Angioletti-Uberti and other researchers considers interparticle and intraparticle DNA hybridization. The scheme consists of two different DNA shells, including one with α and β strands, and another with α' β' strands. Source

Plant lignification is a tightly regulated complex cellular process that occurs via three sequential steps: the synthesis of monolignols within the cytosol; the transport of monomeric precursors across plasma membrane; and the oxidative polymerization of monolignols to form lignin macromolecules within the cell wall. Although we have a reasonable understanding of monolignol biosynthesis, many aspects of lignin assembly remain elusive. These include the precursors' transport and oxidation, and the initiation of lignin polymerization. This review describes our current knowledge of the molecular mechanisms underlying monolignol transport and oxidation, discusses the intriguing yet least-understood aspects of lignin assembly, and highlights the technologies potentially aiding in clarifying the enigma of plant lignification. © 2012 The Author Published by the Molecular Plant Shanghai Editorial Office in association with Oxford University Press on behalf of CSPB and IPPE, SIBS, CAS. Source

Tsvelik A.M.,Brookhaven National Laboratory
Physical Review Letters | Year: 2013

It is shown that a junction of three critical quantum Ising chains (Delta junction) can be described as a two-channel Kondo model with a spin S=1/2 localized at the junction, which is composed of the respective Ising, zero energy boundary Majorana modes. © 2013 American Physical Society. Source

Tkachenko A.V.,Brookhaven National Laboratory
Physical Review Letters | Year: 2011

We present a theoretical analysis of the inverse problem in self-assembly. A particular scheme is proposed for building an arbitrary desired nanostructure out of self-assembled building blocks ("octopus" nanoparticles). The conditions for robust self-assembly of the target structure are identified. This includes the minimal number of "colors" needed to encode interparticle bonds, which are to be implemented as pairs of complementary DNA sequences. As a part of this analysis, it is demonstrated that a floppy network with thermal fluctuations, in a certain range of coordination numbers Z, possesses entropic rigidity and can be described as a traditional elastic solid. The onset of the entropic rigidity, Z=d+1, determines the minimal number of bond types per particle needed to encode the desired structure. Thermodynamic considerations give additional conditions for the implementation of this scheme. © 2011 American Physical Society. Source

Although the practice of protein engineering is industrially fruitful in creating biocatalysts and therapeutic proteins, applications of analogous techniques in the field of plant metabolic engineering are still in their infancy. Lignins are aromatic natural polymers derived from the oxidative polymerization of primarily three different hydroxycinnamyl alcohols, the monolignols. Polymerization of lignin starts with the oxidation of monolignols, followed by endwise cross-coupling of (radicals of) a monolignol and the growing oligomer/polymer. The para-hydroxyl of each monolignol is crucial for radical generation and subsequent coupling. Here, we describe the structure-function analysis and catalytic improvement of an artificial monolignol 4-O-methyltransferase created by iterative saturation mutagenesis and its use in modulating lignin and phenylpropanoid biosynthesis. We show that expressing the created enzyme in planta, thus etherifying the para-hydroxyls of lignin monomeric precursors, denies the derived monolignols any participation in the subsequent coupling process, substantially reducing lignification and, ultimately, lignin content. Concomitantly, the transgenic plants accumulated de novo synthesized 4-O-methylated soluble phenolics and wall-bound esters. The lower lignin levels of transgenic plants resulted in higher saccharification yields. Our study, through a structure-based protein engineering approach, offers a novel strategy for modulating phenylpropanoid/lignin biosynthesis to improve cell wall digestibility and diversify the repertories of biologically active compounds. Source

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