RNA–polypeptide complexes (RNPs), which play various roles in extant biological systems, have been suggested to have been important in the early stages of the molecular evolution of life. At a certain developmental stage of ancient RNPs, their RNA and polypeptide components have been proposed to evolve in a reciprocal manner to establish highly elaborate structures and functions. We have constructed a simple model system, from which a cooperative evolution system of RNA and polypeptide components could be developed. Based on the observation that several RNAs modestly accelerated the chemical ligation of the two basic peptides. We have designed an RNA molecule possessing two peptide binding sites that capture the two peptides. This designed RNA can also accelerate the peptide ligation. The resulting ligated peptide, which has two RNA-binding sites, can in turn function as a trans-acting factor that enhances the endonuclease activity catalyzed by the designed RNA.

Nowadays, coal production increases continuously due to an increase in mechanization in coal mining and demand in its related fields of application worldwide. Coal production in China is especially an increasing trend and a large amount of waste fine coal is produced. Waste fine coals usually contain large amounts of ash and inorganic sulfur due to non-selective coal mining of the coal. Therefore, waste fine coals are available as a resource and cause spontaneous combustion leading in turn to air pollution because of their coal contents and small particle sizes which increases the surface area liable to be wet and oxidized, and the disposal site of waste fine coals cause land occupation, soil pollution and water contamination.In this study, a vegetable oil agglomeration process was performed for coal recovery from Chongqing Nantong waste fine coals in China. The oil agglomeration process has been used to mineral oil of exhaustible resource. Therefore, in this study, several kinds of vegetable oils are selected as oil agglutinative agents because the vegetable oils which are renewable, available and less-pollutant energy resources. The effects of the parameters including particle sizes, agitation conditions, chemical structure and viscosity of vegetable oils were investigated based on the combustible matter recovery, ash reduction and efficiency index. It was concluded that particle sizes of waste fine coal, agitation rate and agitation time will influence on the recovery efficiency of combustible matter from its original waste coal by the colza oil agglomeration. Furthermore, a wide range of vegetable oil alteration grades including prepared waste vegetable oil samples and therefore, of oil properties, such as chemical structural changes and unsaturated carbonaceous functional groups by the oxidation processes in the used waste vegetable oils have to be achieved.

[reaction: see text] A set of mutually interconvertable inner-bridged-type porphyrinoids, imino-fused N-confused porphyrins (IF-NCPs), which possess a [5.7.5] tricyclic ring in the core, were synthesized from a condensation reaction of 21-amino-substituted NCP and an arylaldehyde, and the structures were characterized by X-ray single-crystal analysis.

BackgroundGenetic tools including constitutive and inducible promoters have been developed over the last few decades for strain engineering in Streptomyces. Inducible promoters are useful for controlling gene expression, however only a limited number are applicable to Streptomyces. The aim of this study is to develop a controllable protein expression system based on an inducible promoter using sugar inducer, which has not yet been widely applied in Streptomyces.ResultsTo determine a candidate promoter, inducible protein expression was first examined in Streptomyces avermitilis MA-4680 using various carbon sources. Xylose isomerase (xylA) promoter derived from xylose (xyl) operon was selected due to strong expression of xylose isomerase (XylA) in the presence of d-xylose. Next, a xylose-inducible protein expression system was constructed by investigating heterologous protein expression (chitobiase as a model protein) driven by the xylA promoter in Streptomyces lividans. Chitobiase activity was detected at high levels in S. lividans strain harboring an expression vector with xylA promoter (pXC), under both xylose-induced and non-induced conditions. Thus, S. avermitilis xylR gene, which encodes a putative repressor of xyl operon, was introduced into constructed vectors in order to control protein expression by d-xylose. Among strains constructed in the study, XCPR strain harboring pXCPR vector exhibited strict regulation of protein expression. Chitobiase activity in the XCPR strain was observed to be 24 times higher under xylose-induced conditions than that under non-induced conditions.ConclusionIn this study, a strictly regulated protein expression system was developed based on a xylose-induced system. As far as we could ascertain, this is the first report of engineered inducible protein expression in Streptomyces by means of a xylose-induced system. This system might be applicable for controllable expression of toxic products or in the field of synthetic biology using Streptomyces strains.Electronic supplementary materialThe online version of this article (10.1186/s12934-018-0991-y) contains supplementary material, which is available to authorized users.