Molecular stamping

This German stamp depicts a molecular model of urea and was issued in 1982 to commemorate the bun dredth anniversary of Woh ler s death The computer graphic that opened this in troductory chapter is also a model of urea... 

Gum arabic (gum acacia) is used as the lickable glue on stamps and envelopes, and as a flavor stabilizer (emulsifier) in soft drinks. It has components that bind to water, and components that bind to oils, making it an emulsifier but not a surfactant (because of the high molecular weight). 

Bottino, D., Penland, R.C., Stamps, A., Traebert, M., Dumotier, B., Georgiva, A., Helmlinger, G. and Lett, G.S. (2006) Preclinical cardiac safety assessment of pharmaceutical compounds using an integrated systems-based computer model of the heart. Progress in Biophysics and Molecular Biology, 90, 414-443. 

Depctrins, products of the partial hydrolysis of starch, are polysacchandes of lower molecular weight than starch. They are used in infant food because they are easier to digest than starches. Dextrins are sticky when wet and are used as mucilage on postage stamps and envelopes. 

Lord Rutherford (who was indeed a physicist, as the quote implies) would have been astonished to see this century s transformation of biology from stamp collecting into molecular biology, genomics, biochemistry and biophysics. This transformation occurred only because, time and time again, fundamental advances in theoretical physics drove the development of useful new tools for chemistry. Chemists in turn learned how to synthesize and characterize ever more complex molecules, and eventually created a quantitative framework for understanding biology and medicine. 

Microcontact printing (pCP) is a technique that uses an elastomeric stamp with relief on its surface to generate patterned SAMs on the surface of both planar and curved substrates [87,88]. SAMs are highly ordered molecular assemblies that form spontaneously by chemisorption of functionalized long-chain molecules on the surfaces of appropriate substrates [79,89]. Well-established systems of SAMs include alkanethiolates on coinage metals (Au, Ag, Cu) [90] alkyl-siloxanes on hydroxyl-terminated surfaces (Si/Si02, glass) [91] carboxylic and... 

Figure 11 Atomic Force Microscopy image of aligned PTAA coated insulin fibrils that have been transferred to a glass surface after molecular combing directly onto the surface of a PDMS stamp. The lines have been added to illustrate gaps within the PDMS stamp. The scale bar is 2 mm in length (Herland, Bjdrk et at, 2007). Copyright Wiley-VCH Verlag GmbH Co. KGaA. Reproduced with permission.

In order to improve the stamping resolution of the elasomeric stamp, there have been recent improvements in both the stamp and molecular inks e.g., alkylthiols, silanes). In particular, traditional PDMS exhibits a relatively high elasticity that limits possible relief linewidths on the other hand, small molecular weight inks exhibit diffusion during patterning. Hence, the following complementary strategies have been employed ... 

Fig. 3.8 The gradient approach of Geissler et al.55 A PDMS stamp is used to ink a mixture of MHA (white) and ODT (black) onto a 2D array of silica beads immobilized on a gold substrate (1). Molecules are moving from the stamp to the gold surface with different speed (2). By reaching the gold, the molecules assemble into molecular rings whose composition creates a gradient from the inside to the outside (3)...

Fig. 3.10 Molecular printing of gradients. Thiol diffuses from the PDMS stamp to the gold surface and creates a monolayer gradient. The length of the arrows correlates with the amount of soaked up thiol...

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