1
|
Bioprocess performance analysis of novel methanol-independent promoters for recombinant protein production with Pichia pastoris. Microb Cell Fact 2021; 20:74. [PMID: 33757505 PMCID: PMC7986505 DOI: 10.1186/s12934-021-01564-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 03/12/2021] [Indexed: 11/30/2022] Open
Abstract
Background Pichia pastoris is a powerful and broadly used host for recombinant protein production (RPP), where past bioprocess performance has often been directed with the methanol regulated AOX1 promoter (PAOX1), and the constitutive GAP promoter (PGAP). Since promoters play a crucial role in an expression system and the bioprocess efficiency, innovative alternatives are constantly developed and implemented. Here, a thorough comparative kinetic characterization of two expression systems based on the commercial PDF and UPP promoters (PPDF, PUPP) was first conducted in chemostat cultures. Most promising conditions were subsequently tested in fed-batch cultivations. These new alternatives were compared with the classical strong promoter PGAP, using the Candida antarctica lipase B (CalB) as model protein for expression system performance. Results Both the PPDF and PUPP-based expression systems outperformed similar PGAP-based expression in chemostat cultivations, reaching ninefold higher specific production rates (qp). CALB transcription levels were drastically higher when employing the novel expression systems. This higher expression was also correlated with a marked upregulation of unfolded protein response (UPR) related genes, likely from an increased protein burden in the endoplasmic reticulum (ER). Based on the chemostat results obtained, best culture strategies for both PPDF and PUPP expression systems were also successfully implemented in 15 L fed-batch cultivations where qp and product to biomass yield (YP/X*) values were similar than those obtained in chemostat cultivations. Conclusions As an outcome of the macrokinetic characterization presented, the novel PPDF and PUPP were observed to offer much higher efficiency for CalB production than the widely used PGAP-based methanol-free alternative. Thus, both systems arise as highly productive alternatives for P. pastoris-based RPP bioprocesses. Furthermore, the different expression regulation patterns observed indicate the level of gene expression can be adjusted, or tuned, which is interesting when using Pichia pastoris as a cell factory for different products of interest. Supplementary Information The online version contains supplementary material available at 10.1186/s12934-021-01564-9.
Collapse
|
2
|
Samoudi M, Kuo CC, Robinson CM, Shams-Ud-Doha K, Schinn SM, Kol S, Weiss L, Petersen Bjorn S, Voldborg BG, Rosa Campos A, Lewis NE. In situ detection of protein interactions for recombinant therapeutic enzymes. Biotechnol Bioeng 2021; 118:890-904. [PMID: 33169829 PMCID: PMC7855575 DOI: 10.1002/bit.27621] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 10/20/2020] [Accepted: 10/25/2020] [Indexed: 12/13/2022]
Abstract
Despite their therapeutic potential, many protein drugs remain inaccessible to patients since they are difficult to secrete. Each recombinant protein has unique physicochemical properties and requires different machinery for proper folding, assembly, and posttranslational modifications (PTMs). Here we aimed to identify the machinery supporting recombinant protein secretion by measuring the protein-protein interaction (PPI) networks of four different recombinant proteins (SERPINA1, SERPINC1, SERPING1, and SeAP) with various PTMs and structural motifs using the proximity-dependent biotin identification (BioID) method. We identified PPIs associated with specific features of the secreted proteins using a Bayesian statistical model and found proteins involved in protein folding, disulfide bond formation, and N-glycosylation were positively correlated with the corresponding features of the four model proteins. Among others, oxidative folding enzymes showed the strongest association with disulfide bond formation, supporting their critical roles in proper folding and maintaining the ER stability. Knockdown of disulfide-isomerase PDIA4, a measured interactor with significance for SERPINC1 but not SERPINA1, led to the decreased secretion of SERPINC1, which relies on its extensive disulfide bonds, compared to SERPINA1, which has no disulfide bonds. Proximity-dependent labeling successfully identified the transient interactions supporting synthesis of secreted recombinant proteins and refined our understanding of key molecular mechanisms of the secretory pathway during recombinant protein production.
Collapse
Affiliation(s)
- Mojtaba Samoudi
- Dept of Pediatrics, University of California, San Diego
- Novo Nordisk Foundation Center for Biosustainability at UC San Diego
| | - Chih-Chung Kuo
- Novo Nordisk Foundation Center for Biosustainability at UC San Diego
- Dept of Bioengineering, University of California, San Diego
| | - Caressa M. Robinson
- Novo Nordisk Foundation Center for Biosustainability at UC San Diego
- Dept of Bioengineering, University of California, San Diego
| | | | - Song-Min Schinn
- Dept of Pediatrics, University of California, San Diego
- Novo Nordisk Foundation Center for Biosustainability at UC San Diego
| | - Stefan Kol
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark
| | - Linus Weiss
- Dept of Biochemistry, Eberhard Karls University of Tübingen, Germany
| | - Sara Petersen Bjorn
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark
| | - Bjorn G. Voldborg
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark
| | | | - Nathan E. Lewis
- Dept of Pediatrics, University of California, San Diego
- Novo Nordisk Foundation Center for Biosustainability at UC San Diego
- Dept of Bioengineering, University of California, San Diego
| |
Collapse
|
3
|
Jain AR, Britton ZT, Markwalter CE, Robinson AS. Improved ligand-binding- and signaling-competent human NK2R yields in yeast using a chimera with the rat NK2R C-terminus enable NK2R-G protein signaling platform. Protein Eng Des Sel 2020; 32:459-469. [PMID: 32400863 DOI: 10.1093/protein/gzaa009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Revised: 03/09/2020] [Accepted: 04/16/2020] [Indexed: 02/07/2023] Open
Abstract
The tachykinin 2 receptor (NK2R) plays critical roles in gastrointestinal, respiratory and mental disorders and is a well-recognized target for therapeutic intervention. To date, therapeutics targeting NK2R have failed to meet regulatory agency approval due in large part to the limited characterization of the receptor-ligand interaction and downstream signaling. Herein, we report a protein engineering strategy to improve ligand-binding- and signaling-competent human NK2R that enables a yeast-based NK2R signaling platform by creating chimeras utilizing sequences from rat NK2R. We demonstrate that NK2R chimeras incorporating the rat NK2R C-terminus exhibited improved ligand-binding yields and downstream signaling in engineered yeast strains and mammalian cells, where observed yields were better than 4-fold over wild type. This work builds on our previous studies that suggest exchanging the C-termini of related and well-expressed family members may be a general protein engineering strategy to overcome limitations to ligand-binding and signaling-competent G protein-coupled receptor yields in yeast. We expect these efforts to result in NK2R drug candidates with better characterized signaling properties.
Collapse
Affiliation(s)
- Abhinav R Jain
- Department of Chemical and Biomolecular Engineering, Tulane University, 6823 St Charles Ave, New Orleans, LA, 70118, USA
| | - Zachary T Britton
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy St, Newark, DE, 19716, USA.,AstraZeneca, Antibody Discovery and Protein Engineering, Gaithersburg, MD 20878, USA
| | - Chester E Markwalter
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy St, Newark, DE, 19716, USA.,Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Anne S Robinson
- Department of Chemical and Biomolecular Engineering, Tulane University, 6823 St Charles Ave, New Orleans, LA, 70118, USA.,Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy St, Newark, DE, 19716, USA.,Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| |
Collapse
|
4
|
Jain AR, Robinson AS. Functional Expression of Adenosine A 3 Receptor in Yeast Utilizing a Chimera with the A 2AR C-Terminus. Int J Mol Sci 2020; 21:E4547. [PMID: 32604732 PMCID: PMC7352405 DOI: 10.3390/ijms21124547] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Revised: 06/21/2020] [Accepted: 06/24/2020] [Indexed: 11/26/2022] Open
Abstract
The adenosine A3 receptor (A3R) is the only adenosine receptor subtype to be overexpressed in inflammatory and cancer cells and therefore is considered a novel and promising therapeutic target for inflammatory diseases and cancer. Heterologous expression of A3R at levels to allow biophysical characterization is a major bottleneck in structure-guided drug discovery efforts. Here, we apply protein engineering using chimeric receptors to improve expression and activity in yeast. Previously we had reported improved expression and trafficking of the chimeric A1R variant using a similar approach. In this report, we constructed chimeric A3/A2AR comprising the N-terminus and transmembrane domains from A3R (residues 1-284) and the cytoplasmic C-terminus of the A2AR (residues 291-412). The chimeric receptor showed approximately 2-fold improved expression with a 2-fold decreased unfolded protein response when compared to wild type A3R. Moreover, by varying culture conditions such as initial cell density and induction temperature a further 1.7-fold increase in total receptor yields was obtained. We observed native-like coupling of the chimeric receptor to Gai-Gpa1 in engineered yeast strains, activating the downstream, modified MAPK pathway. This strategy of utilizing chimeric receptor variants in yeast thus provides an exciting opportunity to improve expression and activity of "difficult-to-express" receptors, expanding the opportunity for utilizing yeast in drug discovery.
Collapse
Affiliation(s)
- Abhinav R. Jain
- Department of Chemical and Biomolecular Engineering, Tulane University, 6823 St Charles Ave, New Orleans, LA 70118, USA;
| | - Anne S. Robinson
- Department of Chemical and Biomolecular Engineering, Tulane University, 6823 St Charles Ave, New Orleans, LA 70118, USA;
- Department of Chemical Engineering, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15213, USA
| |
Collapse
|
5
|
Jain AR, Stradley SH, Robinson AS. The A2aR C-terminus provides improved total and active expression yields for adenosine receptor chimeras. AIChE J 2018. [DOI: 10.1002/aic.16398] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Abhinav R. Jain
- Dept. of Chemical and Biomolecular Engineering; Tulane University; New Orleans LA 70118
| | - Steven H. Stradley
- Dept. of Chemical and Biomolecular Engineering; Tulane University; New Orleans LA 70118
| | - Anne S. Robinson
- Dept. of Chemical and Biomolecular Engineering; Tulane University; New Orleans LA 70118
| |
Collapse
|
6
|
O'Brien CJ, Calero‐Rubio C, Razinkov VI, Robinson AS, Roberts CJ. Biophysical characterization and molecular simulation of electrostatically driven self-association of a single-chain antibody. Protein Sci 2018; 27:1275-1285. [PMID: 29637646 PMCID: PMC6032362 DOI: 10.1002/pro.3415] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 03/25/2018] [Accepted: 03/26/2018] [Indexed: 12/30/2022]
Abstract
Colloidal protein-protein interactions (PPI) are often expected to impact key behaviors of proteins in solution, such as aggregation rates and mechanisms, aggregate structure, protein solubility, and solution viscosity. PPI of an anti-fluorescein single chain antibody variable fragment (scFv) were characterized experimentally at low to intermediate ionic strength using a combination of static light scattering and sedimentation equilibrium ultracentrifugation. Surprisingly, the results indicated that interactions were strongly net-attractive and electrostatics promoted self-association. Only repulsive interactions were expected based on prior work and calculations based a homology model of a related scFv crystal structure. However, the crystal structure lacks the charged, net-neutral linker sequence. PyRosetta was used to generate a set of scFv structures with different linker conformations, and coarse-grained Monte Carlo simulations were used to evaluate the effect of different linker configurations via second osmotic virial coefficient (B22 ) simulations. The results show that the configuration of the linker has a significant effect on the calculated B22 values, and can result in strong electrostatic attractions between oppositely charged residues on the protein surface. This is particularly relevant for development of non-natural antibody products, where charged linkers and other loop regions may be prevalent. The results also provide a preliminary computational framework to evaluate the effect of unstructured linkers on experimental protein-protein interaction parameters such as B22 .
Collapse
Affiliation(s)
- Christopher J. O'Brien
- Department of Chemical and Biomolecular EngineeringUniversity of DelawareNewarkDelaware19716
| | - Cesar Calero‐Rubio
- Department of Chemical and Biomolecular EngineeringUniversity of DelawareNewarkDelaware19716
| | | | - Anne S. Robinson
- Department of Chemical and Biomolecular EngineeringUniversity of DelawareNewarkDelaware19716
- Department of Chemical and Biomolecular EngineeringTulane UniversityNew OrleansLos Angeles70118
| | - Christopher J. Roberts
- Department of Chemical and Biomolecular EngineeringUniversity of DelawareNewarkDelaware19716
| |
Collapse
|
7
|
Wang XD, Jiang T, Yu XW, Xu Y. Effects of UPR and ERAD pathway on the prolyl endopeptidase production in Pichia pastoris by controlling of nitrogen source. ACTA ACUST UNITED AC 2017; 44:1053-1063. [DOI: 10.1007/s10295-017-1938-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 02/22/2017] [Indexed: 01/12/2023]
Abstract
Abstract
Prolyl endopeptidase (PEP) is very useful in various industries, while the high cost of enzyme production remains a major obstacle for its industrial applications. Pichia pastoris has been used for the PEP production; however, the fermentation process has not be investigated and little is known about the impact of excessive PEP production on the host cell physiology. Here, we optimized the nitrogen source to improve the PEP expression level and further evaluated the cellular response including UPR and ERAD. During methanol induction phase the PEP activity (1583 U/L) was increased by 1.48-fold under the optimized nitrogen concentration of NH4+ (300 mmol/L) and casamino acids [1.0% (w/v)] in a 3-L bioreactor. Evaluated by RT-PCR the UPR and ERAD pathways were confirmed to be activated. Furthermore, a strong decrease of ERAD-related gene transcription was observed with the addition of nitrogen source, which contributed to a higher PEP expression level.
Collapse
Affiliation(s)
- Xiao-Dong Wang
- 0000 0001 0708 1323 grid.258151.a The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology Jiangnan University 214122 Wuxi People’s Republic of China
- 0000 0001 0708 1323 grid.258151.a State Key Laboratory of Food Science and Technology Jiangnan University 214122 Wuxi People’s Republic of China
| | - Ting Jiang
- 0000 0001 0708 1323 grid.258151.a The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology Jiangnan University 214122 Wuxi People’s Republic of China
- 0000 0001 0708 1323 grid.258151.a State Key Laboratory of Food Science and Technology Jiangnan University 214122 Wuxi People’s Republic of China
| | - Xiao-Wei Yu
- 0000 0001 0708 1323 grid.258151.a The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology Jiangnan University 214122 Wuxi People’s Republic of China
- 0000 0001 0708 1323 grid.258151.a State Key Laboratory of Food Science and Technology Jiangnan University 214122 Wuxi People’s Republic of China
| | - Yan Xu
- 0000 0001 0708 1323 grid.258151.a The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology Jiangnan University 214122 Wuxi People’s Republic of China
- 0000 0001 0708 1323 grid.258151.a State Key Laboratory of Food Science and Technology Jiangnan University 214122 Wuxi People’s Republic of China
| |
Collapse
|
8
|
Yadav DK, Yadav N, Yadav S, Haque S, Tuteja N. An insight into fusion technology aiding efficient recombinant protein production for functional proteomics. Arch Biochem Biophys 2016; 612:57-77. [DOI: 10.1016/j.abb.2016.10.012] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 10/15/2016] [Accepted: 10/18/2016] [Indexed: 11/27/2022]
|
9
|
Blocker KM, Britton ZT, Naranjo AN, McNeely PM, Young CL, Robinson AS. Recombinant G Protein-Coupled Receptor Expression in Saccharomyces cerevisiae for Protein Characterization. Methods Enzymol 2015; 556:165-83. [DOI: 10.1016/bs.mie.2014.12.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
10
|
Delic M, Göngrich R, Mattanovich D, Gasser B. Engineering of protein folding and secretion-strategies to overcome bottlenecks for efficient production of recombinant proteins. Antioxid Redox Signal 2014; 21:414-37. [PMID: 24483278 DOI: 10.1089/ars.2014.5844] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
SIGNIFICANCE Recombinant protein production has developed into a huge market with enormous positive implications for human health and for the future direction of a biobased economy. Limitations in the economic and technical feasibility of production processes are often related to bottlenecks of in vivo protein folding. RECENT ADVANCES Based on cell biological knowledge, some major bottlenecks have been overcome by the overexpression of molecular chaperones and other folding related proteins, or by the deletion of deleterious pathways that may lead to misfolding, mistargeting, or degradation. CRITICAL ISSUES While important success could be achieved by this strategy, the list of reported unsuccessful cases is disappointingly long and obviously dependent on the recombinant protein to be produced. Singular engineering of protein folding steps may not lead to desired results if the pathway suffers from several limitations. In particular, the connection between folding quality control and proteolytic degradation needs further attention. FUTURE DIRECTIONS Based on recent understanding that multiple steps in the folding and secretion pathways limit productivity, synergistic combinations of the cell engineering approaches mentioned earlier need to be explored. In addition, systems biology-based whole cell analysis that also takes energy and redox metabolism into consideration will broaden the knowledge base for future rational engineering strategies.
Collapse
Affiliation(s)
- Marizela Delic
- 1 Department of Biotechnology, University of Natural Resources and Life Sciences (BOKU) , Vienna, Austria
| | | | | | | |
Collapse
|
11
|
Young CL, Raden DL, Robinson AS. Analysis of ER resident proteins in Saccharomyces cerevisiae: implementation of H/KDEL retrieval sequences. Traffic 2013; 14:365-81. [PMID: 23324027 DOI: 10.1111/tra.12041] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Revised: 01/07/2013] [Accepted: 01/16/2013] [Indexed: 01/20/2023]
Abstract
An elaborate quality control system regulates endoplasmic reticulum (ER) homeostasis by ensuring the fidelity of protein synthesis and maturation. In budding yeast, genomic analyses and high-throughput proteomic studies have identified ER resident proteins that restore homeostasis following local perturbations. Yet, how these folding factors modulate stress has been largely unexplored. In this study, we designed a series of polymerase chain reaction (PCR)-based modules including codon-optimized epitopes and fluorescent protein (FP) variants complete with C-terminal H/KDEL retrieval motifs. These conserved sequences are inherent to most soluble ER resident proteins. To monitor multiple proteins simultaneously, H/KDEL cassettes are available with six different selection markers, providing optimal flexibility for live-cell imaging and multicolor labeling in vivo. A single pair of PCR primers can be used for the amplification of these 26 modules, enabling numerous combinations of tags and selection markers. The versatility of pCY H/KDEL cassettes was demonstrated by labeling BiP/Kar2p, Pdi1p and Scj1p with all novel tags, thus providing a direct comparison among FP variants. Furthermore, to advance in vitro studies of yeast ER proteins, Strep-tag II was engineered with a C-terminal retrieval sequence. Here, an efficient purification strategy was established for BiP under physiological conditions.
Collapse
Affiliation(s)
- Carissa L Young
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716, USA
| | | | | |
Collapse
|
12
|
Young CL, Raden DL, Caplan JL, Czymmek KJ, Robinson AS. Cassette series designed for live-cell imaging of proteins and high-resolution techniques in yeast. Yeast 2012; 29:119-36. [PMID: 22473760 DOI: 10.1002/yea.2895] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Accepted: 02/27/2012] [Indexed: 12/22/2022] Open
Abstract
During the past decade, it has become clear that protein function and regulation are highly dependent upon intracellular localization. Although fluorescent protein variants are ubiquitously used to monitor protein dynamics, localization and abundance; fluorescent light microscopy techniques often lack the resolution to explore protein heterogeneity and cellular ultrastructure. Several approaches have been developed to identify, characterize and monitor the spatial localization of proteins and complexes at the suborganelle level, yet many of these techniques have not been applied to yeast. Thus, we have constructed a series of cassettes containing codon-optimized epitope tags, fluorescent protein variants that cover the full spectrum of visible light, a TetCys motif used for fluorescein arsenical hairpin (FlAsH)-based localization, and the first evaluation in yeast of a photoswitchable variant, mEos2, to monitor discrete subpopulations of proteins via confocal microscopy. This series of modules, complete with six different selection markers, provides the optimal flexibility during live-cell imaging and multicolour labelling in vivo. Furthermore, high-resolution imaging techniques include the yeast-enhanced TetCys motif, which is compatible with diaminobenzidine photo-oxidation used for protein localization by electron microscopy, and mEos2, which is ideal for super-resolution microscopy. We have examined the utility of our cassettes by analysing all probes fused to the C-terminus of Sec61, a polytopic membrane protein of the endoplasmic reticulum of moderate protein concentration, in order to directly compare fluorescent probes, their utility and technical applications. Our series of cassettes expand the repertoire of molecular tools available to advance targeted spatiotemporal investigations using multiple live-cell, super-resolution or electron microscopy imaging techniques.
Collapse
Affiliation(s)
- Carissa L Young
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE, USA
| | | | | | | | | |
Collapse
|
13
|
Young CL, Britton ZT, Robinson AS. Recombinant protein expression and purification: A comprehensive review of affinity tags and microbial applications. Biotechnol J 2012; 7:620-34. [DOI: 10.1002/biot.201100155] [Citation(s) in RCA: 312] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Revised: 11/23/2011] [Accepted: 11/29/2011] [Indexed: 12/27/2022]
|