The updated crystalline sponge method

March 9, 2016
The updated crystalline sponge method
Binding modes found in the pore of a crystalline sponge are shown. Credit: Hoshino et al.

X-ray crystallographic analysis is one of the only methods that provides direct information on molecular structures at the atomic level. The method, however, has the intrinsic limitation that the target molecules must be crystalline, and high-quality single crystals must be prepared before measurement.

These limitations have often caused considerable problems for scientists in their determination of . In 2013, a group of scientists reported a revolutionary new technique for single-crystal X-ray diffraction analysis that did not require the crystallisation of samples in the sample preparation [Inokuma et al. (2013), Nature, 495, 461-466]. This method, later coined the crystalline sponge method, uses crystals of porous metal complexes capable of absorbing guest compounds from solution in a common solvent. The guests are efficiently trapped and concentrated at several binding sites in the porous complexes, and the periodic array of the binding sites renders the absorbed guests oriented and observable by common X-ray diffraction studies.

However, the subsequent data quality of the trapped guest compound was not very high and the use of restraints and constraints based on chemical information was necessary to refine the guest structures. The need for this workaround was due purely to unoptimised experimental conditions and protocols. It soon became clear that to develop the crystalline sponge method from basic science into a reliable new technology that might innovate and support the molecular chemistry community, considerable effort was needed to improve the data quality. In addition, the crystallographic scope and limitations in the refinement of structures with large pores—more commonly known as metal-organic framework (MOF) structures—needed to be considered carefully. Over the last two years, therefore, the same group of researchers has made considerable advances in improving the data quality and uncovering the crystallographic scope and limitations for the refinement of guest structures obtained using the crystalline sponge method [Hoshino et al. (2016), IUCrJ, 3, 139-151; DOI: 10.1107/S2052252515024379].

These researchers anticipate renewed interest in the technique and hope further experimentation by the community will improve the quality and value of the protocol.

Explore further: Determining the structures of nanocrystalline pharmaceuticals by electron diffraction

More information: Manabu Hoshino et al. The crystalline sponge method updated, IUCrJ (2016). DOI: 10.1107/S2052252515024379

Related Stories

Twisted X-rays unravel the complexity of helical structures

February 9, 2016

Since the discovery of the diffraction of X-rays by crystals just over 100 years ago, X-ray diffraction as a method of structure determination has dominated structural research in materials science and biology. However, many ...

Breakthrough in chemical crystallography

April 5, 2013

A research team led by Professor Makoto Fujita of the University of Tokyo, Japan, and complemented by Academy Professor Kari Rissanen of the University of Jyväskylä, Finland, has made a fundamental breakthrough in single-crystal ...

Even if imprisoned inside a crystal, molecules can still move

October 6, 2015

X-ray crystallography reveals the three-dimensional structure of a molecule, thus making it possible to understand how it works and potentially use this knowledge to subsequently modulate its activity, especially for therapeutic ...

Aperiodic crystals and beyond

June 17, 2015

Once a contradiction in terms, aperiodic crystals show instead that "long-range order" has never been defined. Whatever it means, decades of intense research have shown it to be more complex and surprising than anyone suspected ...

The complexity of modeling

November 3, 2015

In recent years, advances in materials synthesis techniques have enabled scientists to produce increasingly complex functional materials with enhanced or novel macroscopic properties. For example, ultra-small core-shell metallic ...

Recommended for you

Creating antimatter via lasers?

September 27, 2016

Dramatic advances in laser technologies are enabling novel studies to explore laser-matter interactions at ultrahigh intensity. By focusing high-power laser pulses, electric fields (of orders of magnitude greater than found ...

Cosmic dust demystified

September 27, 2016

The solar system is a dusty environment, with trillions of cosmic dust particles left behind by comets and asteroids that orbit the sun. All this dust forms a relatively dense cloud through which the Earth travels, sweeping ...

Physicists develop a more sensitive microscope

September 27, 2016

Anyone who has taken a photo in a poorly lit restaurant or dim concert venue knows all too well the grainy, fuzzy outcomes of low-light imaging. Scientists trying to take images of biological specimens encounter the same ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.