Crystal macromolecular

Another important sub-case, of disorder in macromolecular crystals, corresponds to the statistical occurrence of two specific orientations only, at well defined positions in a 3-D lattice, of a group of macromolecules or of each single macromolecule. 

Krejchi, M. T., Atkins, E. D., Waddon, A. J., Fournier, M. J., Mason, T. L., and Tirrell, D. A. (1994). Chemical sequence control of beta-sheet assembly in macromolecular crystals of periodic polypeptides. Science 265, 1427-1432. 

The recommendations embodied in this document are concerned with the terminology relating to the structure of crystalline polymers and the process of macromolecular crystallization. The document is limited to systems exhibiting crystallinity in the classical sense of three-dimensionally periodic regularity. The recommendations deal primarily with crystal structures that are comprised of essentially rectilinear, parallel-packed polymer chains, and secondarily, with those composed of so-called globular macromolecules. Since the latter are biological in nature, they are not covered in detail here. In general, macromolecular systems with mesophases are also omitted, but crystalline polymers with conformational disorder are included. 

Figure 3.2 Dispensing of a microbatch trial under oil. The dashed circle represents the initial position of the crystallization drop at the time of dispensing. The grey circle represents the final position of the drop after it had made its way to the bottom of the well (due to its higher density compared to that of the oil). Modified from Chayen (1997). The role of oil in macromolecular crystallization. Structure 5, 1259-1274, Copyright Elsevier.

Transfer of macromolecular crystals into cryostabilization buffer... 

Table 4.1 Antifreeze agents used in the shock cooling of macromolecular crystals...

Preparation of a shock-cooled macromolecular crystal involves the rapid introduction of a loop-mounted sample into a cryogen. Introduction into the cryogen must be rapid in order to ensure that aqueous solvent within the crystal cools as a vitreous... 

Figure 4.1 demonstrates the procedure for moimt-ing a macromolecular crystal in a free-standing fQm, which is supported by a thin fibre loop (Fig. 4.2). 

Figure 4.2 Examples of loop-mounted macromolecular crystals.

Table 44 The 65 space groups that are possible for macromolecular crystals...

Kwong, P. D. and Liu, Y. (1999). Use of cryoprotectants in combination with immiscible oils for flash cooling macromolecular crystals. J. Appl. Cryst. 32,102-105. 

Macromolecular crystals grow in an equilibrium state with their mother liquor. Disrupting this equilibrium can often destroy the crystals or their ability to diffract X-rays. This situation can be exacerbated by the transfer of the crystal to a solution containing a heavy atom. Therefore, it is important, once crystals are removed from their sealed environment, to first transfer them to a stabilizing solution and let them re-equilibrate before further transfer to the heavy atom solution. Usually, a stabilizing solution is identical to the mother liquor in which the crystal was grown, but with a higher concentration of precipitant. 

Murray, J. W, Garman, E. and RavelU, R. (2004). X-ray absorption by macromolecular crystals the effects of wavelength and crystal composition on absorbed dose. /. Appl. Crystallogr. 37, 513-522. 

Nave, C. and Garman, E. F. (2005). Towards an understanding of radiation damage in cryocooled macromolecular crystals. /. Synchrotron Rad. 12,257-260. 

Yao, M., Yasutake, Y. and Tanaka, I. (2004). Hashcooling of macromolecular crystals in a capillary to overcome increased mosaidty. Acta Crystallogr. D 60, 39 5. 

---