The protein homology-based methods are limited however, since some functional regions involve large contact areas that may only be apparent from 3D protein structures and are not obvious from primary sequence alignments [8].
Several studies describe the spatial arrangement for hundreds or thousands of electrosensory pores in different elasmobranch species [33] [39] but most functional analyses are limited to assessment of dorsal and ventral surface pore distributions in relation mainly to their feeding ecology.
These chemical methods are limited because after this treatment the protein is no longer functional.
"Though there are only limited functional data, it appears that the gene is highly expressed in the brain," says Dr. Lu Qi, an assistant professor in the department of nutrition at the Harvard School of Public Health and one of the dozens of scientists who agreed to re-examine his past data for this new analysis.
Studying the function of membrane proteins at the single-molecule level remains a formidable challenge, and to date there is limited number of available functional assays.
While there is anatomical evidence for indirect anatomical pathways linking early visual areas to the hippocampus (Kravitz et al. 2011), there is limited evidence for the functional connections which would be employed during scene perception, and we were interested to test for similarities and differences in connectivity between scene perception and scene construction.
The observation that pulse pressure is of limited functional importance (compared with flow) has allowed the development of miniaturized continuous-flow devices for long-term use.
Only the TGF-β1 gene bound MLL1 in activated HSCs, albeit at a low level, suggesting that there may be some limited functional redundancy between ASH1 and MLL1 in these cells.
Technically, working with non-model organisms means there is limited access to high-throughput functional assays.
Nonetheless, precise knowledge about the neural circuitry involved in tic generation is limited by difficulties de-correlating functional (neuroimaging) activity prior to and during tics (Bohlhalter et al., 2006).
