The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Huiqi Zhang - One of the best experts on this subject based on the ideXlab platform.
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preparation of molecularly imprinted polymer microspheres via reversible addition fragmentation chain transfer precipitation polymerization
Polymer, 2009Co-Authors: Baiyi Zu, Ying Zhang, Chenxi Li, Huiqi ZhangAbstract:The first combined use of reversible addition–fragmentation chain transfer (RAFT) polymerization and precipitation polymerization in the molecular imprinting field is described. The new polymerization technique, namely RAFT precipitation polymerization (RAFTPP), provides MIP microspheres with obvious molecular imprinting effects towards the template, fast template binding process and an appreciable selectivity over structurally related compounds, while only irregular MIP aggregates were obtained via traditional radical precipitation polymerization (TRPP) under similar reaction conditions. The MIP microspheres prepared via RAFTPP have proven to show improved binding capacity, larger binding constant and apparent maximum number for high-affinity sites, and significantly higher high-affinity binding site density in comparison with the MIP prepared via TRPP.
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Preparation of molecularly imprinted polymer microspheres via atom transfer radical precipitation polymerization
Journal of Polymer Science Part A: Polymer Chemistry, 2009Co-Authors: Guoqing Pan, Xianzhi Guo, Ying Zhang, Huiqi ZhangAbstract:The first combined use of atom transfer radical polymerization (ATRP) and precipitation polymerization in the molecular imprinting field is described. The utilized polymerization technique, namely atom transfer radical precipitation poly- merization (ATRPP), provides MIP microspheres with obvious molecular imprinting effects towards the template, fast template binding kinetics and an appreciable selec- tivity over structurally related compounds. The living chain propagation mechanism in ATRPP results in MIP spherical particles with diameters (number-average diame- ter Dn � 3 lm) much larger than those prepared via traditional radical precipitation polymerization (TRPP). In addition, the MIP microspheres prepared via ATRPP have also proven to show significantly higher high-affinity binding site densities on their surfaces than the MIP generated via TRPP, while the binding association constants Ka and apparent maximum numbers Nmax of the high-affinity sites as well as the specific template bindings are almost the same in the two cases. V C 2009 Wiley
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Preparation of molecularly imprinted polymer microspheres via reversible addition–fragmentation chain transfer precipitation polymerization
Polymer, 2009Co-Authors: Guoqing Pan, Xianzhi Guo, Ying Zhang, Huiqi ZhangAbstract:The first combined use of reversible addition–fragmentation chain transfer (RAFT) polymerization and precipitation polymerization in the molecular imprinting field is described. The new polymerization technique, namely RAFT precipitation polymerization (RAFTPP), provides MIP microspheres with obvious molecular imprinting effects towards the template, fast template binding process and an appreciable selectivity over structurally related compounds, while only irregular MIP aggregates were obtained via traditional radical precipitation polymerization (TRPP) under similar reaction conditions. The MIP microspheres prepared via RAFTPP have proven to show improved binding capacity, larger binding constant and apparent maximum number for high-affinity sites, and significantly higher high-affinity binding site density in comparison with the MIP prepared via TRPP.
Patrick Delmas - One of the best experts on this subject based on the ideXlab platform.
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Polycystins: polymodal receptor/ion-channel cellular sensors
Pflügers Archiv, 2005Co-Authors: Patrick DelmasAbstract:Transient receptor potential (TRP) channel proteins are divided into seven subgroups that are currently designated as TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPN (NOMP-C, from no mechanoreceptor potential-C), TRPA (ankyrin-like with transmembrane domains 1) and TRPP (polycystin). TRPC, TRPV and TRPM are related to canonical TRP proteins whereas TRPN, TRPA and TRPP (polycystin) are more divergent. Most TRP channels are linked to sensory stimuli, including phototransduction, thermosensation and mechanosensation. The TRPP subfamily was named after its founding member, polycystin kidney disease-2 (PKD2), a gene product mutated in many cases of autosomal dominant polycystic kidney disease (ADPKD). ADPKD is a major inherited nephropathy, affecting over 1:1,000 of the worldwide population, characterized by the progressive development of fluid-filled cysts from the tubules and collecting ducts of affected kidneys. Loss-of-function mutations in either polycystin-2, a non-selective cation channel, or polycystin-1 (PKD1), a large plasma membrane integral protein, give rise to ADPKD. PKD1 and PKD2 are thought to function together as part of a multiprotein receptor/ion-channel complex or independently and may be involved in transducing Ca^2+-dependent mechanosensitive signals in response to cilia bending in renal epithelial cells and endodermally derived cells. Further information on the growing number and physiological properties of these TRP-polycystins is the basis of this review.
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polycystins polymodal receptor ion channel cellular sensors
Pflügers Archiv: European Journal of Physiology, 2005Co-Authors: Patrick DelmasAbstract:Transient receptor potential (TRP) channel proteins are divided into seven subgroups that are currently designated as TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPN (NOMP-C, from no mechanoreceptor potential-C), TRPA (ankyrin-like with transmembrane domains 1) and TRPP (polycystin). TRPC, TRPV and TRPM are related to canonical TRP proteins whereas TRPN, TRPA and TRPP (polycystin) are more divergent. Most TRP channels are linked to sensory stimuli, including phototransduction, thermosensation and mechanosensation. The TRPP subfamily was named after its founding member, polycystin kidney disease-2 (PKD2), a gene product mutated in many cases of autosomal dominant polycystic kidney disease (ADPKD). ADPKD is a major inherited nephropathy, affecting over 1:1,000 of the worldwide population, characterized by the progressive development of fluid-filled cysts from the tubules and collecting ducts of affected kidneys. Loss-of-function mutations in either polycystin-2, a non-selective cation channel, or polycystin-1 (PKD1), a large plasma membrane integral protein, give rise to ADPKD. PKD1 and PKD2 are thought to function together as part of a multiprotein receptor/ion-channel complex or independently and may be involved in transducing Ca(2+)-dependent mechanosensitive signals in response to cilia bending in renal epithelial cells and endodermally derived cells. Further information on the growing number and physiological properties of these TRP-polycystins is the basis of this review.
Paul Babitzke - One of the best experts on this subject based on the ideXlab platform.
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Translation Control of trpG from Transcripts Originating from the Folate Operon Promoter of Bacillus subtilis Is Influenced by Translation-Mediated Displacement of Bound TRAP, While Translation Control of Transcripts Originating from a Newly Identifi
Journal of bacteriology, 2006Co-Authors: Helen Yakhnin, Alexander V Yakhnin, Paul BabitzkeAbstract:The trpEDCFBA operon of Bacillus subtilis carries six of the seven tryptophan biosynthetic genes and is contained within a larger aromatic amino acid supraoperon (Fig. (Fig.1A).1A). The seventh tryptophan biosynthetic gene, trpG (pabA), is present in a folic acid biosynthesis operon. Expression of the tryptophan biosynthetic genes is regulated in response to tryptophan by trp RNA-binding attenuation protein (TRAP) via transcription attenuation and translation control mechanisms (reviewed in references 3 and 13). TRAP also regulates translation of TRPP, a gene that encodes an apparent tryptophan transporter (22, 29), and ycbK, a gene that shares sequence homology to known efflux protein genes (23, 28). TRAP consists of 11 identical subunits arranged in a single ring (2). When activated by tryptophan, 11 KKR motifs on the perimeter of TRAP interact with multiple NAG trinucleotide repeats in target transcripts, with a preference for N of G ≈ U > A > C, thereby wrapping the RNA around TRAP's perimeter (1, 6, 32). Optimal spacing between triplet repeats is 2 nucleotides (nt) (5, 7), although 1-nt spacers and spacers as large as 14 nt have been observed in natural TRAP targets (Fig. (Fig.1B1B). FIG. 1. Organization of B. subtilis tryptophan metabolism genes and sequence comparison of the four known TRAP binding sites. (A) The six genes of the trp operon, which is part of the aromatic amino acid supraoperon, and trpG encode the tryptophan biosynthetic ... The trpEDCFBA operon leader transcript is capable of folding into mutually exclusive antiterminator and terminator structures that participate in the transcription attenuation mechanism. When activated by tryptophan, TRAP can bind to 11 triplet repeats present in the nascent trp leader transcript (Fig. (Fig.1B).1B). Bound TRAP prevents formation of the antiterminator structure because six of the triplet repeats are present within its stem. As a consequence, formation of the overlapping terminator hairpin causes RNA polymerase (RNAP) to terminate transcription in the leader region. In the absence of TRAP binding, formation of the antiterminator allows transcriptional readthrough into the trp operon structural genes (4, 6, 19). TRAP also regulates translation initiation of trpE (Fig. (Fig.1A).1A). TRAP binding to trp operon readthrough transcripts promotes formation of a trpE Shine-Dalgarno (S-D) sequence-sequestering hairpin. Formation of this RNA structure inhibits translation initiation by preventing ribosome binding (11, 18). A third TRAP-dependent regulatory mechanism is responsible for controlling translation initiation of trpG, ycbK, and TRPP, with bound TRAP directly blocking ribosome binding (12, 18, 22, 23, 28, 29, 31). TrpG functions as a common glutamine amidotransferase subunit in the biosynthesis of both tryptophan and folic acid. TRAP binds to nine triplet repeats that overlap the trpG S-D sequence (Fig. (Fig.1B).1B). The TRAP binding site in the TRPP transcript also contains nine triplet repeats that overlap its S-D sequence (Fig. (Fig.1B).1B). One distinction between TRPP and trpG translation control is that the TRAP binding site in TRPP mRNA extends into the TRPP coding sequence, whereas the TRAP binding site in trpG ends just prior to the coding sequence. TRAP also inhibits translation initiation of ycbK by a similar mechanism; however, in this case, all nine triplet repeats are downstream from the S-D sequence and extend further into the ycbK coding sequence than is the case for TRPP (Fig. (Fig.1B).1B). In addition, expression of a dipeptide-encoding minigene that utilizes the ycbK S-D sequence has a small inhibitory effect on YcbK synthesis (Fig. (Fig.1B)1B) (28). In the present study, we compared the extents of TRAP-mediated translation inhibition of trpG, ycbK, and TRPP. Our results led to the hypothesis that the pabB and trpG gene arrangement might contribute to the low level of TRAP-dependent regulation of trpG. Our data suggest that ribosomes that translate pabB are capable of displacing bound TRAP from the trpG S-D sequence. A new trpG promoter was also identified that is not subject to translation-mediated displacement of bound TRAP.
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the trp rna binding attenuation protein of bacillus subtilis regulates translation of the tryptophan transport gene TRPP yhag by blocking ribosome binding
Journal of Bacteriology, 2004Co-Authors: Helen Yakhnin, Hong Zhang, Alexander V Yakhnin, Paul BabitzkeAbstract:Expression of the Bacillus subtilis tryptophan biosynthetic genes (trpEDCFBA and pabA [trpG]) is regulated in response to tryptophan by TRAP, the trp RNA-binding attenuation protein. TRAP-mediated regulation of the tryptophan biosynthetic genes includes a transcription attenuation and two distinct translation control mechanisms. TRAP also regulates translation of TRPP (yhaG), a single-gene operon that encodes a putative tryptophan transporter. Its translation initiation region contains triplet repeats typical of TRAP-regulated mRNAs. We found that regulation of TRPP and pabA is unaltered in a rho mutant strain. Results from filter binding and gel mobility shift assays demonstrated that TRAP binds specifically to a segment of the TRPP transcript that includes the untranslated leader and translation initiation region. While the affinities of TRAP for the TRPP and pabA transcripts are similar, TRAP-mediated translation control of TRPP is much more extensive than for pabA. RNA footprinting revealed that the TRPP TRAP binding site consists of nine triplet repeats (five GAG, three UAG, and one AAG) that surround and overlap the TRPP Shine-Dalgarno (S-D) sequence and translation start codon. Results from toeprint and RNA-directed cell-free translation experiments indicated that tryptophan-activated TRAP inhibits TRPP synthesis by preventing binding of a 30S ribosomal subunit. Taken together, our results establish that TRAP regulates translation of TRPP by blocking ribosome binding. Thus, TRAP coordinately regulates tryptophan synthesis and transport by three distinct mechanisms: attenuation transcription of the trpEDCFBA operon, promoting formation of the trpE S-D blocking hairpin, and blocking ribosome binding to the pabA and TRPP transcripts.
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Regulation of transcription attenuation and translation initiation by allosteric control of an RNA-binding protein: the Bacillus subtilis TRAP protein.
Current opinion in microbiology, 2004Co-Authors: Paul BabitzkeAbstract:Tryptophan allosterically controls the 11-subunit trp RNA-binding attenuation protein (TRAP) of Bacillus subtilis. When activated by tryptophan, TRAP binds to multiple trinucleotide repeats in target transcripts. TRAP is responsible for the decision to terminate transcription in the leader region of the trpEDCFBA operon or to allow transcription to proceed into the structural genes. TRAP also regulates translation of trpE by promoting formation of an RNA structure that prevents ribosome binding. In addition, bound TRAP regulates translation initiation of pabA, TRPP and ycbK by directly blocking ribosome binding. The anti-TRAP protein inhibits TRAP activity by competing with RNA for the RNA binding surface of TRAP.
Alexis Hofherr - One of the best experts on this subject based on the ideXlab platform.
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The TRPP subfamily and polycystin-1 proteins.
Handbook of experimental pharmacology, 2014Co-Authors: Mariam Semmo, Michael Köttgen, Alexis HofherrAbstract:It has been exciting times since the identification of polycystic kidney disease 1 (PKD1) and PKD2 as the genes mutated in autosomal dominant polycystic kidney disease (ADPKD). Biological roles of the encoded proteins polycystin-1 and TRPP2 have been deduced from phenotypes in ADPKD patients, but recent insights from vertebrate and invertebrate model organisms have significantly expanded our understanding of the physiological functions of these proteins. The identification of additional TRPP (TRPP3 and TRPP5) and polycystin-1-like proteins (PKD1L1, PKD1L2, PKD1L3, and PKDREJ) has added yet another layer of complexity to these fascinating cellular signalling units. TRPP proteins assemble with polycystin-1 family members to form receptor–channel complexes. These protein modules have important biological roles ranging from tubular morphogenesis to determination of left–right asymmetry. The founding members of the polycystin family, TRPP2 and polycystin-1, are a prime example of how studying human disease genes can provide insights into fundamental biological mechanisms using a so-called “reverse translational” approach (from bedside to bench). Here, we discuss the current literature on TRPP ion channels and polycystin-1 family proteins including expression, structure, physical interactions, physiology, and lessons from animal model systems and human disease.
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TRPP Channels and Polycystins
Advances in experimental medicine and biology, 2010Co-Authors: Alexis Hofherr, Michael KöttgenAbstract:The founding member of the TRPP family, TRPP2, was identified as one of the disease genes causing autosomal dominant polycystic kidney disease (ADPKD). ADPKD is the most prevalent, potentially lethal, monogenic disorder in humans, with an average incidence of one in 400 to one in 1,000 individuals worldwide. Here we give an overview of TRPP ion channels and Polycystin-1 receptor proteins focusing on more recent studies. We include the Polycystin-1 family since these proteins are functionally linked to TRPP channels.
Michael Köttgen - One of the best experts on this subject based on the ideXlab platform.
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The TRPP subfamily and polycystin-1 proteins.
Handbook of experimental pharmacology, 2014Co-Authors: Mariam Semmo, Michael Köttgen, Alexis HofherrAbstract:It has been exciting times since the identification of polycystic kidney disease 1 (PKD1) and PKD2 as the genes mutated in autosomal dominant polycystic kidney disease (ADPKD). Biological roles of the encoded proteins polycystin-1 and TRPP2 have been deduced from phenotypes in ADPKD patients, but recent insights from vertebrate and invertebrate model organisms have significantly expanded our understanding of the physiological functions of these proteins. The identification of additional TRPP (TRPP3 and TRPP5) and polycystin-1-like proteins (PKD1L1, PKD1L2, PKD1L3, and PKDREJ) has added yet another layer of complexity to these fascinating cellular signalling units. TRPP proteins assemble with polycystin-1 family members to form receptor–channel complexes. These protein modules have important biological roles ranging from tubular morphogenesis to determination of left–right asymmetry. The founding members of the polycystin family, TRPP2 and polycystin-1, are a prime example of how studying human disease genes can provide insights into fundamental biological mechanisms using a so-called “reverse translational” approach (from bedside to bench). Here, we discuss the current literature on TRPP ion channels and polycystin-1 family proteins including expression, structure, physical interactions, physiology, and lessons from animal model systems and human disease.
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TRPP Channels and Polycystins
Advances in experimental medicine and biology, 2010Co-Authors: Alexis Hofherr, Michael KöttgenAbstract:The founding member of the TRPP family, TRPP2, was identified as one of the disease genes causing autosomal dominant polycystic kidney disease (ADPKD). ADPKD is the most prevalent, potentially lethal, monogenic disorder in humans, with an average incidence of one in 400 to one in 1,000 individuals worldwide. Here we give an overview of TRPP ion channels and Polycystin-1 receptor proteins focusing on more recent studies. We include the Polycystin-1 family since these proteins are functionally linked to TRPP channels.