Host strains or in vitro expression conditions by in-cell, in-gel and immunological detection as well as protein purification by affinity chromatography. Additionally, the marker proteins can be cleaved off by treatment with Tobacco Etch Virus protease recognizing a cognate TEV cleavage site included in all proteins. With the vectors generated here we observed 100% cloning efficiency in almost all experiments, i.e. virtually all LIC-inserted PCR fragments were present in correct orientation after restriction analysis and were free of sequencing Sorafenib errors and out-of-frame fusions after sequencing. Additionally, IFP-labelled fusion proteins were detected in all cases, eight in vitro, eleven in E. coli, five in K. lactis, four in P. pastoris and seven in L. tarentolae. Four IFP fusion proteins expressed in E. coli were used for functionality analysis, resulting in successful purification by 6xHis affinity chromatography and time-dependent TEV protease cleavage of the 6xHis and IFP reporter proteins. Our platform, which requires minimal effort for designing appropriate cloning strategies, allows for simple screening of optimal expression systems and provides a fertile tool for proteomics research. As examples we demonstrate that IFP fusion proteins can be employed for in vitro protein-protein interaction studies as well as for the analysis of DNA-transcription factor interactions, making IFP fusions amenable to highthroughput screening processes. IFP fusion proteins are conveniently detected by infrared imaging in microtiter plates, or after SDS-polyacrylamide gel electrophoresis in cast protein gels. After pull-down, IFP fusion proteins can thus be directly visualized by infrared imaging making additional experimental steps such as western blotting or autoradiography of radioactively labelled proteins frequently used in such studies obsolete. Finally, we demonstrated enzymatic activity of two selected IFP fusion proteins. Our IFP fusion protein tool box offers an easy-to-handle platform for protein expression and facilitates the analysis of protein-protein and protein-DNA interactions. Although modern proteins usually consist of 20 different amino acids, it has been proposed that amino acid members in primitive proteins varied during the early stage of protein evolution. It has been inferred that the primordial genetic code was composed of a smaller set of amino acids because prebiotic synthesis on the primitive earth is thought to have been inadequate for 20 different amino acids. In the coevolution hypothesis, it is proposed that the genetic code coevolved with the amino acid biosynthetic pathways, and additional amino acids were introduced after production through their synthetic pathways. Comparative genome sequence analysis of orthologous proteins in the genomes of bacteria, archaea and eukaryota revealed that the frequencies of Gly.