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Posted: Aug 29, 2014
Plug 'n' play protein crystals
(Nanowerk News) Almost a hundred years ago in 1929 Linus Pauling presented
the famous Pauling’s Rules to describe the principles governing the structure
of complex ionic crystals. These rules essentially describe how the arrangement
of atoms in a crystal is critically dependent on the size of the atoms, their
charge and type of bonding.
According to scientists from the Biohybrid
Materials Group of Aalto University Finland led by Mauri Kostiainen similar
rules can be applied to prepare ionic colloidal crystals consisting of
oppositely charged proteins and virus particles. The results can be applied for
example in packing and protecting virus particles into crystals that mimic
Nature’s own occlusion bodies (protein lattices that pack and protect virus
particles to maintain their long-term infectivity), preparation of
biocompatible metamaterials, biomolecule crystallization and the subsequent
Plug 'n' Play Protein Crystals: Virus-avidin nanoparticle crystal structures.
Viruses, which are commonly perceived only as unwanted
infectious agents delivering diseases, can be used also to our benefit.
Evolution has rendered virus particles with a precisely defined monodisperse structure,
which can be utilized for example as template for nanoparticle synthesis and
assembly or as a vehicle to deliver drugs or other active ingredients to living
organisms. For example in a previous work from the same research group
published in Nano Letters they were able to transfect human cells efficiently
with DNA origami nanostructures encapsulated inside virus particles.
In the present work ("Self-Assembly and Modular Functionalization of Three Dimensional Crystals from Oppositely Charged Proteins") Kostiainen and his research team show that cowpea chlorotic mottle virus (CCMV) particles and
avidin proteins can form crystals simply by mixing the two components at an
optimized electrolyte concentration. The two components are able to
self-assemble into ordered structures due to the charge complementarity
presented on their surface. Using avidin as a structural component offers
several advantages. Most importantly, avidin is able to bind water-soluble
B7-vitamin, biotin, with very high affinity and selectivity. “This enables us
to functionalize the crystals in a modular way with almost any biotin tagged
"We have demonstrated that it is possible to load the crystals with for
example fluorescent dyes, active enzymes and plasmonic gold nanoparticles.
Ultimately, using the avidin-biotin interaction allows us to avoid tedious
covalent modification of the structures and mimic the process of topotactic
intercalation (the insertion of a new component to lattice points of an
existing crystal),” Kostiainen says.
The current work deals with only one type of virus particle.
“In the future, we will be looking into other virus particles and proteins to
‘glue’ them together”, he adds. “ Studying the assembly of for example human
viruses or viruses with other structural topology, such as rod-like particles,
may open further possibilities for biomedical and materials science related