A Reconciled Estimate of Ice-Sheet Mass Balance

the assembly. However, in practice, low yields were already observed for larger designs (up to 24,576 nucleotides attempted thus far). Solving this challenge may require improvements in structure and sequence design, enzymatic synthesis for higher-quality strands, optimized thermal or isothermal (44) annealing conditions, and a detailed understanding and perhaps explicit engineering of the kinetic assembly pathways (8, 14, 44) of DNA brick structures. The DNA brick structure, with its modular architecture, sophisticated geometry control, and synthetic nature, will further expand the range of applications and challenges that nucleic acid nanotechnology has already started to address for example, to arrange technologically relevant guest molecules into functional devices (6, 25 , 32-34); to serve as programmable molecular probes and instruments for biological studies (33, 34, 36), to render spatial control for biosynthesis of usefill products (25), to function as smart drug delivery particles (37), and to enable high-throughput nanofabrication of complex inorganic materials for electronics or photonics applications (6, 32). The modularity of the brick structure may facilitate rapid prototyping of diverse functional nanodevices. Its sophisticated and refined geometrical control may enable applications that require highprecision arrangements of guest molecules. Because the brick structure is composed entirely of short synthetic strands (no biologically derived scaffold), it is conceivable to make bricks by using synthetic informational polymers other than the natural form of DNA. Such polymers may include L-DNA (26), DNA with chemically modified backbones or artificial bases, or chemically synthesized or in vitro (or even in vivo) transcribed RNA. This material diversity may potentially produce nanostructures with not only prescribed shapes but also designer chemical (or biochemical) properties (such as nuclease resistance or reduced immunogenicity) that would be useful for diverse applications requiring the structure to function robustly in complex environments, such as in living cells or organisms.