What about the recently-published engineered DNA crystal:
Nature. 2009 Sep 3;461(7260):74-7.
From molecular to macroscopic via the rational design of a
self-assembled 3D DNA crystal.
Zheng J, Birktoft JJ, Chen Y, Wang T, Sha R, Constantinou PE, Ginell
SL, Mao C, Seeman NC.
Source
Department of Chemistry, New York University, New York 10003, USA.
Abstract
We live in a macroscopic three-dimensional (3D) world, but our best
description of the structure of matter is at the atomic and molecular
scale. Understanding the relationship between the two scales requires
a bridge from the molecular world to the macroscopic world. Connecting
these two domains with atomic precision is a central goal of the
natural sciences, but it requires high spatial control of the 3D
structure of matter. The simplest practical route to producing
precisely designed 3D macroscopic objects is to form a crystalline
arrangement by self-assembly, because such a periodic array has only
conceptually simple requirements: a motif that has a robust 3D
structure, dominant affinity interactions between parts of the motif
when it self-associates, and predictable structures for these affinity
interactions. Fulfilling these three criteria to produce a 3D periodic
system is not easy, but should readily be achieved with
well-structured branched DNA motifs tailed by sticky ends.
Complementary sticky ends associate with each other preferentially and
assume the well-known B-DNA structure when they do so; the helically
repeating nature of DNA facilitates the construction of a periodic
array. It is essential that the directions of propagation associated
with the sticky ends do not share the same plane, but extend to form a
3D arrangement of matter. Here we report the crystal structure at 4 A
resolution of a designed, self-assembled, 3D crystal based on the DNA
tensegrity triangle. The data demonstrate clearly that it is possible
to design and self-assemble a well-ordered macromolecular 3D
crystalline lattice with precise control.
PMID: 19727196 [PubMed - indexed for MEDLINE] PMCID: PMC2764300 Free PMC Article
On Wed, Jun 29, 2011 at 7:42 PM, Michael Thompson <[log in to unmask]> wrote:
> Hi Paul,
>
> While crystal contacts are typically of a non-covalent nature, there are some exceptions. A disulfide bond can act as a crystal contact, which is a covalent interaction. A technique called synthetic symmetrization involves the engineering of single cysteine mutants, followed by oxidation to form an intermolecular disulfide bond that lies on a 2-fold symmetry axis between the two monomers. The original goal of this technique was to turn an asymmetric monomer into a symmetric dimer, which should crystallize more readily if the artificial 2-fold lies on a crystallographic symmetry axis. Recently, a paper illustrated that even if the artificial 2-fold axis does not become a crystallographic axis, the introduction of a disulfide can create artificial "crystal contacts," which also aid in crystallization. Check out the following paper. There is a nice figure that shows two protein molecules that are really not touching with the exception of the engineered disulfide bond that forms the only contact.
>
> Protein Sci. 2011 Jan;20(1):168-78.
> Synthetic symmetrization in the crystallization and structure determination of CelA from Thermotoga maritima.
>
> HTH,
>
> Mike
>
>
>
>
> ----- Original Message -----
> From: "Paul Lindblom" <[log in to unmask]>
> To: [log in to unmask]
> Sent: Wednesday, June 29, 2011 2:22:26 PM GMT -08:00 US/Canada Pacific
> Subject: [ccp4bb] The Good and the Bad crystal contact?
>
> Hi everybody,
>
> can anybody tell me how crystal contacts are defined? Are there good and bad crystal contacts? They are the most important interactions with impact on the crystal quality, but they are not of covalent nature, arenīt they?
>
> With best regards,
>
> Paul
>
> --
> Michael C. Thompson
>
> Graduate Student
>
> Biochemistry & Molecular Biology Division
>
> Department of Chemistry & Biochemistry
>
> University of California, Los Angeles
>
> [log in to unmask]
>
--
*******************************************
Jacob Pearson Keller
Northwestern University
Medical Scientist Training Program
cel: 773.608.9185
email: [log in to unmask]
*******************************************
|