Symmetry in Protein Quaternary Structure and Polyominoes 2) Upon random mutations these symmetric phenotypes are much more likely to arise as potential variation ( 12, 13), so that a strong bias toward symmetry may emerge even without natural selection for symmetry. This higher compressibility reduces constraints on genotypes, implying that more genotypes will map to simpler, more symmetric phenotypes than to more complex asymmetric ones ( 2, 3). An intuitive explanation for this algorithmic bias toward symmetry proceeds in two steps: 1) Symmetric phenotypes typically need less information to encode algorithmically, due to repetition of subunits. High symmetry can, in turn, be linked to low K( p) ( 6, 9– 11). Instead, highly general (but rather abstract) arguments based on the coding theorem of algorithmic information theory (AIT) ( 7) predict that the P( p) of many GP maps should be highly biased toward phenotypes with low Kolmogorov complexity K( p) ( 8). This does not, however, mean that the probability P( p) that a GP map produces a phenotype p upon random sampling of genotypes will be anything like a uniformly random distribution. Genetic mutations are random in the sense that they occur independently of the phenotypic variation they produce. Lower descriptional complexity also correlates with higher mutational robustness, which may aid the evolution of complex modular assemblies of multiple components. ![]() We test these predictions with extensive biological data, showing that protein complexes, RNA secondary structures, and a model gene regulatory network all exhibit the expected exponential bias toward simpler (and more symmetric) phenotypes. A preference for symmetry is a special case of this bias toward compressible descriptions. Arguments from algorithmic information theory can formalize this intuition, leading to the prediction that many genotype–phenotype maps are exponentially biased toward phenotypes with low descriptional complexity. ![]() It suggests that symmetric structures preferentially arise not just due to natural selection but also because they require less specific information to encode and are therefore much more likely to appear as phenotypic variation through random mutations. Here we introduce an alternative nonadaptive hypothesis based on an algorithmic picture of evolution. However, evolution, unlike engineers, cannot plan ahead, and so these traits must also afford some immediate selective advantage which is hard to reconcile with the breadth of systems where symmetry is observed. It can be tempting to assume-by analogy to engineering design-that symmetry and modularity arise from natural selection. Biological structures also frequently exhibit modularity and symmetry, but the origin of such trends is much less well understood. Those products will contain an inset specifying the limits of use.Engineers routinely design systems to be modular and symmetric in order to increase robustness to perturbations and to facilitate alterations at a later date. Some PTFE membrane containing products may be limited to specific applications. Sample Filtration Prior to UHPLC, HPLC and Mass Spec Filtration of Hard-to-Filter Samples Membrane options include low-protein binding Durapore® PVDF, high throughput Express PES, and nylon. ![]() Millex Filters from Samplicity ® G2 incorporate a simple adapter funnel to 33mm Millex filters enabling easy, vacuum-driven filtration. The Samplicity® G2 system allows processing of samples as small as 300µl. The Samplicity ® G2 system requires virtually no manual force for filtration, which reduces the stress and strain associated with manual filtration through syringe filters or other pressure-driven devices - especially with high viscosity samples.īecause the Samplicity ® G2 Filtration System is powered by vacuum, you can expect more of your sample to be retrieved after filtration. ![]() This accelerates your sample filtration by as much as 35%. The Samplicity ® G2 Filtration System simultaneously filters between 1 and 8 samples. Just attach a vacuum pump, load samples with a standard pipettor, and flip the lever to recover particulate-free samples-even those with high viscosity or particulates-in seconds. The easy to use Samplicity ® G2 system is the first vacuum-driven system with the designed in flexibility to filter 1 to 8 samples directly into standard HPLC vials. The Samplicity ® G2 Filtration System is an innovative new technology that provides a convenient, high throughput alternative to syringe-tip filters when preparing samples for chromatography.
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