Dr. Gerald E. Wuenschell’s favorite structure is:

PCNA

PCNA

Why?

PCNA is a molecule of elegant symmetry, with major functionalities distributed in 3-fold fashion around the central “hole” lined with positively charged residues (orange in the image) ideally suited for threading a DNA molecule, with its negative surface, through it when acting as one of its many functions – a sliding clamp.—Dr. Gerald E. Wuenschell

Robert D. Blackledge’s favorite structure is:

Bismuth

Bismuth

Source: Image by Micha L. Rieser

Why?

Looking at the photo it’s obvious that their beauty and geometric symmetry are the main reasons my favorite crystals are those formed by bismuth. However, other metals also form beautiful crystals with interesting symmetry. But bismuth may be obtained cheaply and is comparatively safe to work with and handle. A teach may divide a class into several groups and have each group grow bismuth crystals, but have each group grow their crystals with one condition (example, cooling rate) different from the other groups. The images of the crystals grown by each group could be viewed and their digital images captured by a smart phone. Then an app on the smart phone could measure the length and width of the top of each hopper-like crystal, calculate the area of each, and determine the mean area for the crystals by each group and the standard deviation in the mean area for the crystals of each group. Comparing the results of the various groups would lead to a class discussion of statistics and of the possible effects on crystal size of each of the varying conditions. These same experiments would be of great interest to hobbyists wanting to grow bismuth crystals for insertion into items of jewelry.—Robert D. Blackledge

Michael Tsapatsis’s favorite structure is:

zeolite MFI

MFI

Source:
http://izasc.ethz.ch/fmi/xsl/IZA-SC/ftc_main_image.xsl?-db=Atlas_main&-lay=fw&STC=MFI&-find

Why?

Zeolite MFI revolutionized the chemical process industry as a catalyst and adsorbent and continues to surprise with new and emerging applications and structural variations. It is also prototypical of a series of templated zeolites which continue to find new applications in catalysis and separations. At the time of its discovery, it was also one of the most complex inorganic structures. Moreover, it included an organic cation in the pores making it a prototype of self assembled nanostructure. —Michael Tsapatsis

Kuthuru Suresh’s favorite structure is:

Andrographolide-Salicylic acid pharmaceutical cocrystal

AP-SLA cocrystal

Source: Kuthuru Suresh, N. Rajesh Goud, and Ashwini Nangia., Chem. Asian J., 2013, 8, 3032 – 3041

Why?

Bitter pill: Andrographolide the bioactive agent used in traditional medicine in China, India, and South Asian countries. It is derived from the plant leaves of Andrographis paniculata . The local plant name in India is Kalmegh. A significant drop in the bioavailability of Andrographolide is due to transformation to its metabolite namely 14-deoxy-12-(R)-sulfo andrographolide isolated from humans and rats. The bioactive agent andrographolide was screened with pharmaceutically acceptable coformers to discover a novel solid form that will solve the chemical instability and poor solubility problems of this herbal medicine. Liquid-assisted grinding of andrographolide with GRAS (generally regarded as safe) coformers in a fixed stoichiometry resulted in cocrystals with vanillin(1:1), vanillic acid (1:1), salicylic acid (1:1), resorcinol (1:1), and guaiacol(1:1). All the crystalline products were characterized by thermal, spectroscopic, and diffraction methods. Interestingly, even though the cocrystals are isostructural, their physicochemical properties are quite different. The andrographolide–salicylic acid cocrystal completely inhibited the chemical transformation of andrographolide to its inactive sulfate metabolite, and the cocrystal exhibited a three times faster dissolution rate than pure andrographolide. This is a rare example of a pharmaceutical cocrystal that resists the chemical transformation that would otherwise make the drug inactive.—Kuthuru Suresh

Ethan Charles Blocher-Smith’s favorite structure is:

CsXeF7

CsXeF7

Source: http://openmopac.net/PM7_accuracy/data_solids/Cesium_xenon_heptafluoride__CsXeF7___ICSD_404986__jmol_XRay_fs.html

Why?

Not only does this compound include an alkali metal, a halogen, and a noble gas (traditionally unexpected), but it also violates the octet rule, adopting the rarely-seen monocapped octahedron for the XeF7- anion. In addition, in the absence of solvent at 50°C it readily decays into Cs2XeF8 (stable to 400°C) and the unstable XeF6. Even a hint of water and this will decay into the highly explosive XeO3.—Ethan Charles Blocher-Smith

Tim Munsie’s favorite structure is:

Fd3m/227/Pyrochlores

Fd3m:227:Pyrochlores

Source: Photo from our lab of a stained glass pyrochlore made by the parent of one of the undergraduate researchers

Why?

The reason my favourite group is the pyrochlores is because of the wide range of physics that comes out of the underlying symmetries, especially when it comes to magnetic frustration. It is easy to explain magnetism and symmetry to almost anyone with this structure. In addition, as group names go pyrochlore just sounds impressive, and personally a pyrochlore was the very first crystal I have grown from base powders into a single crystal.—Tim Munsie

S. Sudalai Kumar’s favorite structure is:

Clonixin (BIXGIY)

Clonixin (BIXGIY)

Source: S. Sudalai Kumar and A. Nangia, Cryst. Growth Des., 2014, 14 (4), 1865–1881

Why?

This is the first polymorphic system reported for neutral and zwitterionic polymorphism in the crystal structure data base. These zwitterionic polymorphs are rare in ampholytes and have pharmaceutical importance of high solubility and stability compared to neutral polymorphs. Several drugs are amphoteric in nature. This structural-cum-solubility study of neutral and zwitterionic polymorphs provides methods for their preparation and a comparison of solubility–stability characteristics. Normally solubility and stability are inversely related for drug polymorphs. We show that the twin characteristics of high solubility and good stability may be jointly optimized in the same zwitterionic polymorph for amphoteric drugs. The high polarity and ionic nature of acidic/ basic groups promote hydrogen bonding with water (for higher solubility) as well as a tighter crystal lattice of ionized molecules (polymorph stability). All the crystal structures were fully characterized by FT-IR, Raman and ss-NMR as well as powder X-ray diffraction line pattern. The thermodynamic relationships and phase transition between the neutral and zwitterionic polymorphs was analyzed by DSC and VT-PXRD. This study provides a new direction to crystallize ionic polymorphs of amphoteric drugs for solubility enhancement. The selective crystallization of zwitterionic forms could be possible through crystallization promoter additives.—S. Sudalai Kumar

William Dichtel’s favorite structure is:

NPN-1

NPN-1

Source: Nature Chemistry (cropped from original)

Why?

This crystal structure was the first covalent organic framework to be isolated as a single crystal suitable for x-ray diffraction, ushering in a future of designed polymeric solids. I hope to see many more in the future!

Ref: Wuest and coworkers, Nature Chemistry, 2013, 5, 830–834.—William Dichtel

Frank Hoffmann’s favorite structure is:

Fencooperite

Fencooperite

Source: own work, made with VESTA

Why?

In my opinion one of the most beautiful nested structures, with many triangular appearing structural units, the planar CO3 units in the centered
channels, alternating pointing up- and downwards giving a six-fold appearance and then a kind of 3D Sierpinski triangles around them, hexagonal arranged, in between as glue the Ba atoms! Great!—Frank Hoffmann

P. Shing Ho’s favorite structure is:

DNA Double-helix

DNA Double-helix

Source: Photo taken of model in office

Why?

DNA—the structure that launched a thousand startups. Although the original
Watson-Crick model would not be called a "crystal structure" by
today's standards (it is consistent with the X-ray fiber diffraction
pattern, but was not solved directly from the X-ray data), the model has been
supported by multiple single crystal structures (of DNA alone or in complexes
with proteins), and has lead to an explosion (a virtual alphabet soup) of
related conformations, the majority of which have been discovered through
crystallography. It is the one structure that nearly every high school student
and company CEO knows, and has seen starring roles in films (from Jurassic Park
to the Hulk), on television (from Nova to the Big Bang Theory), and in comic
strips (from Bloom County to Zits). DNA is probably the most referenced
structure in journals and magazines, even in Chemical and Engineering News.
Thus, DNA structure reaches far beyond science, to science fiction and
non-science, and to, unfortunately in some cases, nonsense.—P. Shing
Ho

Jeffrey Bacon’s favorite structure is:

C60@10-cycloparaphenylene

C60@10-cycloparaphenylene

Source: Xia, J. et al. Chem. Sci. 2012, 3, 3018

Why?

There are many structures of various species encapsulated within fullerenes, but this one turns the tables — buckyball is captured inside a cycloparaphenylene with near-ideal pi-pi interactions all the way around.—Jeffrey Bacon

Lindsey Pruden’s favorite structure is:

NaCl-FCC

NaCl-FCC

Source: Wikipedia

Why?

Since I was a child, the crystal structure of salt (NaCl) has always been my
favorite. One of the reasons for this is because I find it fascinating how
orderly and straight the unit cell is. I find it interesting when looking at at
a ball-and-stick type model of NaCl because it reminds me of looking into an
infinity type mirror. I am also intrigued by sharpness of the corners and how
straight the edges can be. Even though the NaCl unit cell is simple, it is
amazing to me how something so simple can be so important for living organisms.
These are the reasons why I find the salt crystal beautiful.—Lindsey
Pruden

Clara Magalhaes’s favorite structure is:

apatite

apatite

Source:
http://upload.wikimedia.org/wikipedia/commons/c/cb/Fluorapatite-3D-vdW.png

Why?

it is an amazing structure. This solid phase is present in vertebrates' bones and teeth, accomodate many different ions and can be used to stabilize hazardous  elements in environment. Fluorapatite is particularly stable and structure is shown.—Clara Magalhaes

Sean Depner’s favorite structure is:

Tetragonal ZrO2 (space group: P42/nmc)

Why?

This crystal structure leads to many applications like high-K gate dielectrics leading to the future of computers, smart phones and other electronics. Also, there is potential in super elasticity, ferroelasticity, and shape memory.  If pressure is applied, a martensitic phase transformation to the monoclinic structure occurs.  If the pressure continues, defect twin plan wall movement may occur, and finally, with even more increased pressure is applied, elastic deformation results. Remarkably, if the elastic deformation is not too severe, once the pressure is released the tetragonal phase and original shape is restored!

The possibilities for this crystal structure is limitless at the nanoscale!—Sean Depner

Mitch’s favorite structure is:

one showing the rearrangement of a trans-fenestrane

Why?

Following the failure of a Swiss group to synthesize a trans, cis cis cis [5.5.5.5] fenestrane, they published a paper purporting to ‘prove’ that the synthesis of a [5.5.5.5] fenestrane with a trans bond was theoretically impossible. The crystal structure clearly showed that, in fact, the Stanford group had, indeed synthesized one.—Mitch

Kayla Green’s favorite structure is:

photosynthetic reaction center structure in membrane

Why?

I had the great pleasure of getting to know Dr. Johann Deisenhofer during my post-doc at UTSW.  He was awarded the 1988 Nobel prize determining the structure of an intermembrane protein and I enjoyed hearing about his early career.  Although I am a small molecule crystallographer, this structure reminds me of the wonderful man and scientist that I unexpectedly had the pleasure of getting to know at UTSW.  —Kayla Green

Byron Delabarre’s favorite structure is:

Carbonic Anhydrase

CA-rasmol

Source: http://www.rcsb.org/pdb/education_discussion/molecule_of_the_month/images/CA-rasmol.gif

Why?

Maybe not so sexy compared to DNA, ribosome & GPCR structures we see touted as the major achievements of structural biology, but carbonic anhydrase was the first protein structure I ever studied in detail.  I had just started a
graduate course in bioinorganic chemistry where I had decided to cover proteins using Zinc at the active site.  I had never taken a biology or biochemistry course prior to this, thinking myself strictly a synthetic organic chemist. I was hooked immediately by the language, the images and of course the amazing science.  That particular protein structure started me on a path of structural biology understanding that has served me for nearly 20 years now. Even cooler that it came from the lab of T. Alwyn Jones, whose program ‘O’ was a source of frustration (seriously, who names a command after a hobbit? ‘sam_atom_in’!), but mostly delight as a companion when I started solving my own structures.—Byron Delabarre

Alexandre Giguere’s favorite structure is:

1QD7

Source: Nature

Why?

Bacterial resistance to antibiotic compounds is a growing problem the world will have to face in the next century. The knowledge of how some antibiotics affect the ribosome is and will be of primordial importance in the fight against resistant bacteria. Several other structures of antibiotics bounded ribosome have been produced by Ramakrishnan et al. during that time.
Nature, VOL 400, 26., p. 833—Alexandre Giguere

Jes Sherman’s favorite structure is:

Pentacene

ink

Source: Mine, and I have a higher-resolution image of the design if that’s preferred.

Why?

Pentacene is one of the lab rats of organic electronics. It has been widely studied in the solid state, grown into thin films, and derivatized for improved solubility or different packing or more interesting electronic properties. The structure that is tattooed on my back is not surprising, crystallographically—there are plenty of organic compounds that crystallize in triclinic space groups and exhibit herringbone packing motifs. It is not even the only crystal structure reported for this molecule.  Like many compounds, pentacene exhibits several polymorphs; this one is observed in single crystals.

This structure is not my favorite because of the molecule itself, but because of all the research it has enabled—including my own PhD investigations. Crystal structures provide great insight into the physical properties of organic semiconductors. We can use the information in a .cif file to calculate electronic structure or predict crystal habit. Beyond single crystal structure determination, diffraction data are useful in exploring interesting physical properties such as negative thermal expansion (which pentacene exhibits along its a axis) and determining how well ordered thin films are. In the right hands, a crystal structure is a very useful tool.—Jes Sherman


Terry Bigioni’s favorite structure is:

Na4Ag44(pMBA)30

Na4Ag44(pMBA)30 favorite crystal structure copy

Source: Nature Materials

Why?

Crystals of the molecular silver nanoparticle Na4Ag44(pMBA)30 are the first molecular framework materials made from nanoparticles, which is a new class of materials. Approximately 50% of the volume of the crystal is void space. When compressed, the crystal becomes a molecular machine with concerted mechanical motion of its building blocks. This surprising and dramatic collective motion leads to a negative Poisson ratio. Auxetic materials such as this are very rare and can have very different properties than conventional materials. A mechanical study of this material appears in the August 2014 issue of Nature Materials.

The crystal structure of individual Na4Ag44(pMBA)30 molecular nanoparticles is also very important as it gives the first detailed view of the Ag-S interface, which is extremely important for understanding the nature and chemistry of thiolated silver nanoparticles. It also happens that this nanoparticle is the first to be produced on a massive scale in pure form, with a 140 gram batch demonstrated. Further, this nanoparticle is anomalously stable, more stable than even gold nanoparticles of the same class. This was reported in the September 19, 2013 issue of Nature.

The Na4Ag44(pMBA)30 crystal structure is my favorite for what it is and for what it can DO.—Terry Bigioni


Claire Tessier’s favorite structure is:

[Cr(CO)5(PPh2(CH2)4OAl(CH2SiMe3)2]2

OM-83-1128-[Cr(CO)5(PPh2(CH2)4OAl(CH2SiMe3)2]2

Source: I generated the picture from the CIF file in the Cambridge Crystallographic Database that is associted with the reference: Organometallics 1983,2, 1128-1138.

Why?

This crystal structure is important to me for several reasons:
1) It was pivotal for understanding the THF cleavage that was occurring in my PhD research project. The structure shows an opened THF molecule in between the Al and P atoms.
2) It was the first published collaborative work between my husband (Wiley Youngs) and me. He was the crystallographer and at the time was also a grad student.  We have been collaborating ever since (~86 publications).
3) It was the first published collaborative work between my husband’s (Churchill) and my (Beachley) research advisors.  They went on to publish a total of ~33 papers together.
The crystal structure was published in C. Tessier-Youngs, Wiley J. Youngs, 0. T. Beachley, Jr., and Melvyn Rowen Churchill Organometallics 1983,2, 1128-1138. —Claire Tessier


Divneet Kaur’s favorite structure is:

methyl α-(5,6-dimethoxycarbonyl-2,3-dimethoxyazepin-7-ylidene)-α-[5-methoxycarbonyl-2,3-dimethoxypyrid-6-yl)acetate

Viswamayene

Source: Eswaran et al, J. Het. Chem., 1996, 33(4), 1333

Why?

The compound is also called as ‘Viswamayene’. The crystal is one of its kind of a small organic molecule with M.Wt= 534. It is a highly unusual compound in its formation and structure and is formed from a ‘long lived’ singlet nitrene species generated from a tetra substituted aryl azide. The compound is formed via a concomitant ring expansion and ring extrusion reaction, thereby leading to a formation of a pyridyl carbene species from a nitrene. The unusual and un-precedented reaction finds no alternative in literature and forms the basis of another set of rather similar unusual compounds reported from my laboratory which is also a part of my Ph.D thesis work. I feel, that X-ray played a crucial role in determining the exact structure of the compound as NMR techniques were not too sophisticated at that time. The compound gives a rare evidence for the formation of a pyridyl group from a benzene molecule by a series of rearrangements. I, thus feel that this highly unusual molecule has no precedence in literature and hence should be highlighted and recognised for its rare mechanism of formation. —Divneet Kaur


Isaac Yonemoto’s favorite structure is:

Insulin Hexamer (1ai0)

Insulin Hexamer (1ai0)

Source: Selfmade, using PyMol

Why?

I’ve loved this structure for over 8 years (I made the similar one, derived from an NMR structure, featured on insulin wikipedia page since ’06). Despite extreme effort to obtain beautiful crystals – some were even grown on the space shuttle – EM diffraction shows no evidence that insulin is crystalline in higher therians. The b-chain strands are in an antiparallel beta sheet, tantalizingly wrong for understanding parallel beta-sheet amyloid assembly of insulin, which occurs via these residues. A hyperconserved lysine (except, oddly, in rodent insulin 1) is very likely salt bridging in ‘real insulin’ but is seen in an artefactual cystallographic interactions in this structure. A calcium ion, believed to reside in biological formulations, is missing, because the inclusion of calcium ions leads to uncontrollable precipitation. In short, these structures, discovered relatively early and continously refined, are symbolic of the human tendency to seek beauty over reality, and for that reason I love it, C3- and pseudo-C2 symmetries and all. But beauty may not necessarily be useless: These structures have been instrumental in guiding the design of the bestiary of reformulated insulins over the decades. —Isaac Yonemoto


Kate Stafford’s favorite structure is:

Ribonuclease H1 (2QK9)

Ribonuclease H1 (2QK9)

Source: Kate Stafford

Why?

It’s my PhD protein! RNase H is an enzyme that cleaves DNA-RNA hybrids that is found in all domains of life. RNases H from mesophilic and thermophilic bacteria were among the first homologous structures solved from organisms adapted to different temperatures and are structurally very similar despite large differences in enzymatic activity. My work used molecular dynamics simulations to interpret NMR measurements of these proteins’ internal dynamics to better understand the relationship between motion, function, and thermal adaptation.

The PDB code cited above (2QK9) is that of the human RNase H homolog, which was solved in the presence of a hybrid substrate.

RNase H is essential in higher eukaryotes, so everyone reading this has a functional one. It is also essential for the proliferation of retroviruses, making selective inhibitors of the retroviral RNase H domain a potential drug target for novel HIV treatments.

The attached photo is the human RNase H 3D printed with Shapeways. —Kate Stafford


Ashutosh Jogalekar’s favorite structure is:

Alpha hemolysin

Alpha hemolysin

Source: Wikipedia (PDB code 7ahl)

Why?

Alpha hemolysin is one of the very few protein structures that’s not only breathtakingly pretty and intricate but which is also the epicenter of a true technological breakthrough.

The entire structure resembles a flower and traverses a membrane. Beta sheets run along each other to form a 14-strand beta barrel ‘stem’ while other beta sheets line up next to each other at the rim to form the ‘petals’. Both these substructures enclose a remarkable, 100 A long solvent-filled channel. And most impressively, all these subunits self-assemble.

The practical reason why alpha hemolysin is so fascinating is because it is the linchpin of next generation DNA sequencing technology. By utilizing the solvent-filled channel as a nanopore, researchers are threading DNA strands through it and sequencing individual nucleotide bases by looking at minute changes in electrical current across the pore. The technology has already been commercialized and promises to reduce both the cost and time of sequencing.

Alpha hemolysin is thus one of the most perfect examples of combining elegant form with breakthrough technological function. It’s as good an example as I know of nature’s unsurpassed ability to create both beauty and utility in one fell swoop. —Ashutosh Jogalekar


Pennarun’s favorite structure is:

Snowflakes hexagonal struture

Snowflakes hexagonal struture

Source: http://en.wikipedia.org/wiki/X-ray_crystallography#mediaviewer/File:Snowflake8.png

Why?

Water is one of the simplest molecule on earth and essential to life. Well known molecule, it is in the same time a molecule that still not completely known when grouped with other water molecule. Snowflakes show broad number of structures, from which mechanical behavior will depend. Macroscopic mechanical behavior of snow, especially in montains, depends then only of the weak very small hydrogen bonds. In the same time not so weak as USA think to use it with wood fibers to build armor for warships as strong as metallic ones during the WWII. —Pennarun


Marc Armbrster’s favorite structure is:

CuAl2

CuAl2

Source: My PhD thesis :-)

Why?

The intermetallic compound CuAl2 helped to reveal that the chemical bonding depends on the elements in a series of isostructural compounds and not on the crystal struture. Besides, it is one of the best examples that simple metals like copper and aluminum can form beautiful crystal structures upon compound formation! —Marc Armbrster


Xin Su’s favorite structure is:

Insulin/4-hydroxybenzamide on space mission STS-60

Insulin/4-hydroxybenzamide on space mission STS-60

Source: PDB

Why?

Despite many insulin crystal structures you may find in the Protein Data Bank, this one is extraterrestrially exotic. In addition to its exquisite beauty, grown under microgravity aboard the Space Shuttle Discovery, the high-quality crystal enabled scientists to reveal the fine details about drug-insulin interactions, which would have been impossible with earth-grown ones. —Xin Su


Kelly Tyrrell’s favorite structure is:

MreB

Evolution of the cytoskeleton JCB

Source: The Journal of Cell Biology

Why?

Prior to the advent of x-ray crystallography, one of the defining characteristics of prokaryotes was “lacks a cytoskeleton.” However, when the crystal structure of bacterial MreB was found, scientists discovered that MreB and eukaryotic actin “look” nearly identical. It turned that notion completely upside down, rewriting textbooks, and scientists have been studying these homologs – and the evolutionary origins of these proteins – ever since. —Kelly Tyrrell