Click chemistry Now and Then

Click chemistry "now and then" by numbers

No intention to be exclusive or "scientific", this is to perform a simple "statistical" count on click chemistry application in different areas . A "historical" view is provided by comparing two periods, 1999-2007 for "then" and 2011 ( Jan 1 - June 12) for "now". The data for the first period was from Sharpless laboratory's compilation of click chemistry (937 articles). The data for the second period was from a Chemical Abstract search (525 articles). 

Published articles titles were searched by selected key words and the counts are recorded as a simplified reflection of research intensity or trend. The format is "key word / number from 1st period / number from 2nd period.   

click /415/308
click chemistry /262/178
poly- /389/371
polymer /173/253
dendrimer /37/15
material /17/52
dye /2/6
fluorescence & fluorescent / 12/14
cyclodextrin /4/12
drug /26/21
inhibitor /34/25
enzyme /16/6
screen /9/3
combinatorial /10/1
Sharpless /105/1
Huisgen /22/3
synthesis /315/150
cycloaddition /121/24
nano /51/71
epoxide /9/0
triazole /129/47
Diels-Alder /12/2
water /34/9
ligation /21/5
conjugate /49/46
bioconjugate /16/21
oligo /26/16
DNA /24/18
protein /48/29
peptide /51/32
glyco /64/53
sugar /7/7

The first period was roughly the rising and maturation of click chemistry over a few years (937) while the second is the application of click chemistry in many fields in merely half a year (525). Although to obvious dissatisfaction of statisticians it is safe to conclude that click chemistry is much more widely used now than then.  
                                                       

Cholesterol & protein studied by Click chemistry

Chemical Communications Received 31st October 2010, Accepted 21st December 2010 DOI: 10.1039/c0cc04710d

Tate and coworkers from Imperial College London reported the bioorthogonal click chemistry of a fluorescent alkyne probe with azido-modified post-translationally cholesterylated proteins - in living cells. The design is shown in the drawing. This enables rapid multiplexed fluorescence detection and affinity labelling of protein cholesterylation. This method, in comparison with the current radiolabeling, offers safety, speed, sensitivity, and flexibility. It may allow the observation of protein cholesterylation over space and time using fluorescence microscopy.

In more complex and challenging environment, click chemistry has found application and success, only due to its extremely high efficiency and orthogonality.
                                         

Enzyme-linked click chemistry assay for GOAT

cat-ELCCA, enzyme-linked click chemistry assay, was developed by Janda Group for high througput assay of GOAT, Ghrelin O-Acetyl transferase. The methodology is depicted in the drawing. The following chemistries are elegantly combined for the assay: biotin-straptavidin binding, CuAAC click chemistry, HRP catalysis, O-acetyltransferase catalysis, and fluorogenic reaction.

The method should accelerate identification of inhibitors for GOAT, which activates ghrelin by esterification with a C-8 fatty acid unit. It intimately relates to the effort of seeking agents that lower ghrelin levels as obesity or diabetes treatments.

Much like the cat-ELISA assays in immunology, cat-ELCCA, should find applications in other acyltransferases.

Angew. Chem. Int. Ed. 2010, 9630.
                                                     

Active Motif offers click chemistry reagents

Active Motif offers research kits, assays, and the TimeLogic® biocomputing systems. Now it has extended to click chemistry reagents such as Chromeo™ Dyes for bioorthogonal labeling.

Active Motif was founded in 1999 and is headquartered in Carlsbad, California, and has international offices in Tokyo, Japan and Brussels, Belgium.

A collection of vendors with similar offerings was compiled previously:
Click Chemistry: Reagent Vendors Matter (February 8, 2010)

                                         

Click chemistry in protein fatty acylation and prenylation

Nature Chemical Biology, Published online June 17, 2010 

The above and many other click chemistry reagents were chemically synthesized, metabolically or enzymatically introduced into target proteins to effect extremely sensitive detection, by western blotting or in-gel fluorescence. The applications of these probes are: identifying new lipid-modified proteins, analyzing the lipid content of cellular proteins, imaging lipid-modified proteins in cells, and tools for protein labeling in vitro. 

The success lies on the qualities of click chemistry: reaction efficiency, functional group and reaction condition tolerance,  small size of azido and alkenyl groups, etc.