The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
The requested identity is verified. In E. coli K-12, phoA encodes the classical precursor of alkaline phosphatase (PhoA; EC 3.1.3.1), a phosphate-starvation-induced, broad-specificity phosphomonoesterase that becomes active after export to the periplasm. A modern folding study explicitly used UniProt P00634 residue numbering, while organism-specific biochemical studies consistently identify the same protein as the periplasmic, zinc-containing alkaline phosphatase encoded by phoA. Its experimentally established catalytic fold and activity agree with the supplied Alkaline_phosphatase/PF00245 and InterPro domain assignments. No literature concerning a different organism’s similarly named gene was used to infer this annotation. (kamitani1992identificationandcharacterization pages 1-2, elfageih2020cotranslationalfoldingof pages 1-2)
| Annotation facet | Evidence-backed conclusion | Evidence type/strength |
|---|---|---|
| Identity | phoA / UniProt P00634 is the classical alkaline phosphatase of Escherichia coli K-12; a modern study explicitly uses P00634 residue numbering. (elfageih2020cotranslationalfoldingof pages 1-2) | Accession-linked primary evidence; strong |
| Molecular function/reaction | Hydrolase (EC 3.1.3.1) converting a phosphate monoester plus water to the corresponding alcohol and inorganic phosphate; catalysis proceeds through a covalent phosphoseryl intermediate and can support transphosphorylation. (zakataeva2021microbial5′nucleotidasestheir pages 7-9, boulanger2003characterizationofa pages 1-1) | Biochemical and mechanistic evidence; strong |
| Substrate scope | Broad, relatively nonspecific activity toward phosphate monoesters, including organophosphates and 5′-ribonucleotides and probably 5′-deoxyribonucleotides. (zakataeva2021microbial5′nucleotidasestheir pages 7-9, gardner2019controlofthe pages 4-5) | Enzymology and review synthesis; strong for broad scope, substrate-dependent for individual compounds |
| Localization/biogenesis | Synthesized with a 22-residue N-terminal export signal, translocated across the inner membrane, and matured in the periplasm by signal-peptide removal, metal incorporation, folding, and DsbA-dependent formation of two intramolecular disulfides per subunit. Cytoplasmically retained PhoA is inactive. (kamitani1992identificationandcharacterization pages 1-2, kamitani1992identificationandcharacterization pages 4-5) | Export, mutational, biochemical, and folding experiments; strong |
| Oligomer/cofactors | Active enzyme is a homodimer. Each active site contains two Zn²⁺ and one Mg²⁺; dimerization promotes metal binding, stability, and catalysis. (boulanger2003characterizationofa pages 1-1, kamitani1992identificationandcharacterization pages 4-5) | Structural and biochemical evidence; strong |
| Pathway regulation | A Pho-regulon effector: Pi limitation promotes PhoR autophosphorylation and phosphotransfer to PhoB; phospho-PhoB binds promoter Pho boxes and activates phoA. Under Pi sufficiency, PstSCAB–PhoU favors PhoR phosphatase signaling and repression. (gardner2019controlofthe pages 13-14, gardner2019controlofthe pages 4-5, gardner2019controlofthe pages 10-11) | Genetic, biochemical, and authoritative review evidence; strong, although the precise starvation signal remains under study |
| Physiological role | Periplasmic PhoA hydrolyzes externally available or nontransportable organophosphates, releasing Pi that can be imported during phosphorus limitation; it is an acquisition/scavenging enzyme rather than the primary phosphate sensor. (torriani1990fromcellmembrane pages 1-2, gardner2019controlofthe pages 4-5, wanner1993generegulationby pages 1-2) | Physiological and regulatory evidence; strong |
| Quantitative benchmarks | Pho regulon activation is reported below approximately 0.4 μM environmental Pi; intracellular Pi is typically 1–10 mM; some regulon genes are induced >100-fold. Wild-type PhoA showed kcat ≈ 65 s⁻¹ and Km ≈ 23 μM for pNPP under reported assay conditions. Monomerizing T59R reduced activity 10⁴-fold and lowered melting temperature from 97°C to 43°C. (gardner2019controlofthe pages 1-2, wanner1993generegulationby pages 1-2, gardner2019controlofthe pages 10-11, boulanger2003characterizationofa pages 1-1, muller2001improvingescherichiacoli pages 5-6) | Quantitative regulatory and enzymology studies; strong within stated experimental conditions |
| Recent 2023–2024 developments/applications | A 2023 review expanded the phosphate-starvation stress-network context without revising PhoA’s core annotation. In 2024, PhoA fusion activity remained in active use for experimentally mapping membrane-protein topology, including the periplasmic orientation of TrhA termini; established applications also include localization/topology reporters and phosphate-responsive expression systems. (melchionna2024trhaabacterial pages 16-18, gardner2019controlofthe pages 14-16) | Recent application and expert synthesis; strong for reporter use, no major 2023–2024 revision of native catalytic function identified |
Table: Compact evidence map for the identity, molecular function, localization, regulation, physiology, quantitative properties, and recent applications of E. coli K-12 PhoA (P00634).
The literature supports all mandatory identity checks:
Annotation confidence is high for molecular function, periplasmic localization, oligomerization, metal dependence, maturation, and Pho-regulon membership.
PhoA is an alkaline phosphomonoesterase:
phosphate monoester + H₂O → alcohol + inorganic orthophosphate (Pi)
It hydrolyzes the P–O bond of phosphate monoesters and releases Pi. In appropriate reaction mixtures, it can instead transfer the phosphoryl group to an alcohol acceptor—transphosphorylation—rather than exclusively to water. (zakataeva2021microbial5′nucleotidasestheir pages 7-9, boulanger2003characterizationofa pages 1-1)
PhoA is best annotated as a broad-specificity or nonspecific phosphomonoesterase, not as an enzyme dedicated to one metabolite. Documented substrate classes include diverse organophosphate monoesters, 5′-ribonucleotides, and probably 5′-deoxyribonucleotides. The physiological commonality is the exposed phosphate monoester, rather than a narrowly recognized organic leaving group. (zakataeva2021microbial5′nucleotidasestheir pages 7-9, gardner2019controlofthe pages 4-5)
This broad scope explains why synthetic substrates such as p-nitrophenyl phosphate (pNPP) are useful assays but should not be mistaken for the unique physiological substrate. Likewise, PhoA activity toward nucleotides does not make it primarily a dedicated 5′-nucleotidase.
Active PhoA is a metalloenzyme. Each subunit’s active site binds two Zn²⁺ ions and one Mg²⁺ ion. Catalysis proceeds through a covalent phosphoseryl intermediate: the catalytic serine attacks phosphorus, the leaving-group alcohol departs, and the phosphoenzyme is subsequently hydrolyzed to release Pi and regenerate the enzyme. The three metals organize the phosphoryl group, activate catalytic groups/water, and stabilize charge during transfer. (zakataeva2021microbial5′nucleotidasestheir pages 7-9, boulanger2003characterizationofa pages 1-1, muller2001improvingescherichiacoli pages 5-6)
A reported wild-type pNPP turnover number was approximately 65 s⁻¹ under the study’s optimized conditions. Because alkaline-phosphatase kinetics vary strongly with pH, metals, ionic strength, substrate, and product phosphate, this value is an assay benchmark rather than an invariant physiological rate. The source’s extracted reporting of the corresponding Michaelis constant is internally inconsistent in its unit transcription, so that value is not relied upon here. (muller2001improvingescherichiacoli pages 5-6, muller2001improvingescherichiacoli pages 6-7)
PhoA carries out its native function in the periplasm, between the inner and outer membranes. This location places the enzyme where it can hydrolyze organophosphates that reach the periplasm but cannot themselves cross the inner membrane, releasing Pi for uptake. Thus, PhoA is an extracellular-facing nutrient-scavenging enzyme in physiological terms, but it is not normally a freely secreted extracellular enzyme. (torriani1990fromcellmembrane pages 1-2, gardner2019controlofthe pages 4-5)
PhoA is synthesized as a precursor with an N-terminal 22-residue signal peptide. Its maturation includes translocation across the cytoplasmic membrane, removal of the signal peptide, oxidative folding, metal incorporation, and dimerization. Cytoplasmically retained PhoA is inactive and protease-sensitive, demonstrating that the oxidizing periplasmic environment and export pathway are integral to functional activation rather than merely determining address. (kamitani1992identificationandcharacterization pages 1-2)
Each mature subunit contains two intramolecular disulfide bonds. DsbA—originally characterized in this context as PpfA—is required for efficient cysteine oxidation and correct PhoA folding. Disrupting this pathway causes accumulation of reduced, unfolded, protease-sensitive PhoA; one such mutant retained only about 30% of wild-type PhoA activity. (kamitani1992identificationandcharacterization pages 1-2, kamitani1992identificationandcharacterization pages 4-5, kamitani1992identificationandcharacterization pages 3-4)
Modern force-profile experiments further indicate that PhoA begins folding cotranslationally in the periplasm through at least two disulfide-stabilized intermediates, arising when approximately 330 and 360 mature-protein residues have emerged. Folding-generated force was transmitted roughly 160 Å back to the ribosomal catalytic center. These results refine PhoA biogenesis without changing its established function. Protein Science, August 2020, DOI: https://doi.org/10.1002/pro.3927. (elfageih2020cotranslationalfoldingof pages 1-2)
Mature PhoA is an active homodimer. The two active sites lie approximately 32 Šapart. The dimer interface involves about 86 residues, approximately 20% of the protein, buries roughly 2,900 Ų, and contains 26 hydrogen-bonding interactions. (boulanger2003characterizationofa pages 1-1)
Dimerization is functionally important. A T59R substitution produced a largely metal-depleted monomer with approximately 10⁴-fold lower activity and a melting temperature of 43°C, compared with 97°C for wild-type dimeric PhoA. The mutant retained broadly similar secondary structure, indicating that dimer formation specifically stabilizes the active, metal-binding conformation rather than merely preventing wholesale unfolding. Journal of Biological Chemistry, June 2003, DOI: https://doi.org/10.1074/jbc.M301105200. (boulanger2003characterizationofa pages 1-1)
PhoA is an effector enzyme of the Pho phosphate-starvation regulon. It does not itself sense phosphate. The central control machinery comprises:
Under phosphorus limitation, PhoR kinase activity increases, PhoR transfers phosphoryl groups to PhoB, and phospho-PhoB binds promoter Pho boxes to recruit RNA polymerase and induce phosphate-acquisition genes. phoA is described as a relatively later regulon output, after early induction of the PstSCAB–PhoU uptake/homeostasis machinery. (gardner2019controlofthe pages 13-14, gardner2019controlofthe pages 4-5)
Under phosphate sufficiency, PstSCAB–PhoU favors PhoR’s phospho-PhoB phosphatase state, repressing the regulon. Loss of PstSCAB regulation can therefore produce constitutive Pho-regulon expression even in phosphate-rich medium; complete phoU loss can cause uncontrolled phosphate accumulation and severe growth defects. (gardner2019controlofthe pages 4-5, gardner2019controlofthe pages 10-11)
PhoA expands the phosphorus sources available to the cell. It cleaves periplasmically accessible, poorly transportable organophosphates to produce free Pi, which can then be imported by phosphate transport systems. Its precise role is therefore phosphorus scavenging during limitation, complementary to uptake systems and pathways for alternative phosphorus compounds such as glycerol phosphates and phosphonates. (torriani1990fromcellmembrane pages 1-2, gardner2019controlofthe pages 4-5, wanner1993generegulationby pages 1-2)
Quantitative regulatory context includes:
These figures are condition- and study-dependent and should not be treated as universal switching constants.
The authoritative 2019 EcoSal Plus synthesis treats PhoR/PhoB with PstSCAB–PhoU as the core E. coli phosphate-homeostasis circuit but emphasizes that the exact signal transmitted to PhoR remains incompletely resolved. Transporter conformation, transport activity, PhoU-mediated interactions, and intracellular phosphorus sufficiency may all contribute. DOI: https://doi.org/10.1128/ecosalplus.ESP-0006-2019. (gardner2019controlofthe pages 13-14, gardner2019controlofthe pages 10-11)
A 2023 review of phosphate-starved E. coli K-12 focused on the interaction between phosphate limitation and broader stress programs. The established PhoA annotation remains unchanged: PhoA is still the periplasmic phosphomonoesterase effector, whereas ppGpp, DksA, σS, small RNAs, and related regulators explain wider stationary-phase and stress consequences. Moreau, Microbiology, March 2023, DOI: https://doi.org/10.1099/mic.0.001312. Related E. coli evidence connects Pi limitation to SpoT-dependent ppGpp accumulation, DksA-mediated transcriptional reprogramming, and σS stabilization. (gardner2019controlofthe pages 14-16)
A 2024 Salmonella enterica study concluded that PhoBR responds principally to intracellular phosphorus insufficiency, because Pi-free medium did not activate the system when alternative phosphorus sources maintained intracellular supply. This is mechanistically relevant to closely related enteric bacteria and supports a cytoplasmic-sufficiency model, but it is comparative evidence, not direct proof that every detail applies identically to E. coli P00634 regulation. mBio, September 2024, DOI: https://doi.org/10.1128/mbio.01642-24. (bruna2024anintracellularphosphorusstarvation pages 1-3)
Overall, 2023–2024 work refined the network and sensing context; it did not reveal a new native substrate, cellular location, or primary catalytic function for E. coli PhoA.
PhoA is highly active only after export to an oxidizing extracytoplasmic compartment. Consequently, PhoA fusions are widely used to determine whether a fusion point in a membrane protein faces the periplasm. High fusion activity supports periplasmic exposure; low activity is consistent with cytoplasmic placement, subject to controls for expression and folding.
This remains a current experimental application. A January 2024 Journal of Bacteriology study used C-terminal TrhA–PhoA constructs, including multiple site-directed variants, to assess TrhA membrane orientation; qualitative reporter experiments were repeated at least three times. DOI: https://doi.org/10.1128/jb.00397-23. (melchionna2024trhaabacterial pages 16-18)
PhoA is a standard experimental substrate for studying Sec-dependent export, signal-peptide function, periplasmic disulfide formation, DsbA activity, cotranslational folding, and envelope proteostasis. Its strong compartment dependence makes loss or gain of activity a convenient functional readout of these processes. (kamitani1992identificationandcharacterization pages 1-2, kamitani1992identificationandcharacterization pages 4-5, elfageih2020cotranslationalfoldingof pages 1-2)
The phoA promoter has been used to drive heterologous expression after phosphate depletion, enabling growth and production phases to be separated without adding an expensive chemical inducer. This is attractive in fermentation because phosphate exhaustion can provide process-linked induction, although phosphate limitation also changes central metabolism and growth and therefore requires careful optimization. (shimizu2013metabolicregulationof pages 19-20)
PhoA’s robust colorimetric/chemiluminescent activity supports immunoenzymatic fusion and detection systems. Protein engineering has greatly increased catalytic output: a D153G/D330N enzyme reached a reported kcat of 3,202 ± 75 s⁻¹, approximately 40–50 times wild-type activity under the study conditions, while retaining much of the bacterial enzyme’s thermostability. ChemBioChem, August 2001, DOI: https://doi.org/10.1002/1439-7633(20010803)2:7/8%3C517::AID-CBIC517%3E3.0.CO;2-H. (muller2001improvingescherichiacoli pages 5-6, muller2001improvingescherichiacoli pages 6-7)
These applications exploit PhoA’s chemistry or compartment-dependent maturation; they do not imply additional native functions in K-12.
Recommended annotation: phoA encodes a Sec-exported precursor of a periplasmic, disulfide-containing homodimeric alkaline phosphatase. Each active site uses two Zn²⁺ and one Mg²⁺ to hydrolyze a broad range of phosphate monoesters through a covalent phosphoseryl intermediate, releasing inorganic phosphate and the corresponding alcohol; transphosphorylation can also occur. Expression is activated by phospho-PhoB during phosphorus limitation and repressed through the PhoR–PstSCAB–PhoU homeostasis system during phosphate sufficiency. Its principal physiological role is to liberate Pi from periplasmically accessible organophosphates for cellular uptake. (zakataeva2021microbial5′nucleotidasestheir pages 7-9, gardner2019controlofthe pages 4-5, boulanger2003characterizationofa pages 1-1)
The evidence for this annotation is direct and strong: classical genetics, purified-enzyme biochemistry, metal and quaternary-structure studies, mutagenesis, periplasmic-folding experiments, and modern cotranslational-folding measurements all converge on the same function and localization.
References
(kamitani1992identificationandcharacterization pages 1-2): S. Kamitani, Y. Akiyama, and Koreaki Ito. Identification and characterization of an escherichia coli gene required for the formation of correctly folded alkaline phosphatase, a periplasmic enzyme. The EMBO Journal, 11:57-62, Jan 1992. URL: https://doi.org/10.1002/j.1460-2075.1992.tb05027.x, doi:10.1002/j.1460-2075.1992.tb05027.x. This article has 366 citations.
(elfageih2020cotranslationalfoldingof pages 1-2): Rageia Elfageih, Alexandros Karyolaimos, Grant Kemp, Jan‐Willem de Gier, Gunnar von Heijne, and Renuka Kudva. Cotranslational folding of alkaline phosphatase in the periplasm of
(zakataeva2021microbial5′nucleotidasestheir pages 7-9): Natalia P. Zakataeva. Microbial 5′-nucleotidases: their characteristics, roles in cellular metabolism, and possible practical applications. Applied Microbiology and Biotechnology, 105:7661-7681, Sep 2021. URL: https://doi.org/10.1007/s00253-021-11547-w, doi:10.1007/s00253-021-11547-w. This article has 52 citations and is from a domain leading peer-reviewed journal.
(boulanger2003characterizationofa pages 1-1): Robert R. Boulanger and Evan R. Kantrowitz. Characterization of a monomeric escherichia coli alkaline phosphatase formed upon a single amino acid substitution*. Journal of Biological Chemistry, 278:23497-23501, Jun 2003. URL: https://doi.org/10.1074/jbc.m301105200, doi:10.1074/jbc.m301105200. This article has 107 citations and is from a domain leading peer-reviewed journal.
(gardner2019controlofthe pages 4-5): Stewart G. Gardner and William R. McCleary. Control of the phobr regulon in escherichia coli. Dec 2019. URL: https://doi.org/10.1128/ecosalplus.esp-0006-2019, doi:10.1128/ecosalplus.esp-0006-2019. This article has 83 citations.
(kamitani1992identificationandcharacterization pages 4-5): S. Kamitani, Y. Akiyama, and Koreaki Ito. Identification and characterization of an escherichia coli gene required for the formation of correctly folded alkaline phosphatase, a periplasmic enzyme. The EMBO Journal, 11:57-62, Jan 1992. URL: https://doi.org/10.1002/j.1460-2075.1992.tb05027.x, doi:10.1002/j.1460-2075.1992.tb05027.x. This article has 366 citations.
(gardner2019controlofthe pages 13-14): Stewart G. Gardner and William R. McCleary. Control of the phobr regulon in escherichia coli. Dec 2019. URL: https://doi.org/10.1128/ecosalplus.esp-0006-2019, doi:10.1128/ecosalplus.esp-0006-2019. This article has 83 citations.
(gardner2019controlofthe pages 10-11): Stewart G. Gardner and William R. McCleary. Control of the phobr regulon in escherichia coli. Dec 2019. URL: https://doi.org/10.1128/ecosalplus.esp-0006-2019, doi:10.1128/ecosalplus.esp-0006-2019. This article has 83 citations.
(torriani1990fromcellmembrane pages 1-2): Annamaria Torriani. From cell membrane to nucleotides: the phosphate regulon in escherichia coli. BioEssays, 12:371-376, Aug 1990. URL: https://doi.org/10.1002/bies.950120804, doi:10.1002/bies.950120804. This article has 153 citations and is from a peer-reviewed journal.
(wanner1993generegulationby pages 1-2): B. L. Wanner. Gene regulation by phosphate in enteric bacteria. Journal of Cellular Biochemistry, 51:47-54, Jan 1993. URL: https://doi.org/10.1002/jcb.240510110, doi:10.1002/jcb.240510110. This article has 599 citations and is from a peer-reviewed journal.
(gardner2019controlofthe pages 1-2): Stewart G. Gardner and William R. McCleary. Control of the phobr regulon in escherichia coli. Dec 2019. URL: https://doi.org/10.1128/ecosalplus.esp-0006-2019, doi:10.1128/ecosalplus.esp-0006-2019. This article has 83 citations.
(muller2001improvingescherichiacoli pages 5-6): Bruno H. Muller, Claire Lamoure, Marie-Hélène Le Du, Laurence Cattolico, Evelyne Lajeunesse, Fabrice Lemaître, Arween Pearson, Frédéric Ducancel, André Ménez, and Jean-Claude Boulain. Improving escherichia coli alkaline phosphatase efficacy by additional mutations inside and outside the catalytic pocket. ChemBioChem, 2:517-523, Aug 2001. URL: https://doi.org/10.1002/1439-7633(20010803)2:7/8<517::aid-cbic517>3.0.co;2-h, doi:10.1002/1439-7633(20010803)2:7/8<517::aid-cbic517>3.0.co;2-h. This article has 89 citations and is from a peer-reviewed journal.
(melchionna2024trhaabacterial pages 16-18): Maddison Melchionna, Elena E. Ganusova, Neyland Harmon, and Gladys Alexandre. Trha, a bacterial progestin and adiponectin receptor homolog, couples membrane energetics homeostasis and unsaturated fatty acid metabolism. Jan 2024. URL: https://doi.org/10.1128/jb.00397-23, doi:10.1128/jb.00397-23. This article has 2 citations and is from a peer-reviewed journal.
(gardner2019controlofthe pages 14-16): Stewart G. Gardner and William R. McCleary. Control of the phobr regulon in escherichia coli. Dec 2019. URL: https://doi.org/10.1128/ecosalplus.esp-0006-2019, doi:10.1128/ecosalplus.esp-0006-2019. This article has 83 citations.
(torriani1990fromcellmembrane pages 2-3): Annamaria Torriani. From cell membrane to nucleotides: the phosphate regulon in escherichia coli. BioEssays, 12:371-376, Aug 1990. URL: https://doi.org/10.1002/bies.950120804, doi:10.1002/bies.950120804. This article has 153 citations and is from a peer-reviewed journal.
(muller2001improvingescherichiacoli pages 6-7): Bruno H. Muller, Claire Lamoure, Marie-Hélène Le Du, Laurence Cattolico, Evelyne Lajeunesse, Fabrice Lemaître, Arween Pearson, Frédéric Ducancel, André Ménez, and Jean-Claude Boulain. Improving escherichia coli alkaline phosphatase efficacy by additional mutations inside and outside the catalytic pocket. ChemBioChem, 2:517-523, Aug 2001. URL: https://doi.org/10.1002/1439-7633(20010803)2:7/8<517::aid-cbic517>3.0.co;2-h, doi:10.1002/1439-7633(20010803)2:7/8<517::aid-cbic517>3.0.co;2-h. This article has 89 citations and is from a peer-reviewed journal.
(kamitani1992identificationandcharacterization pages 3-4): S. Kamitani, Y. Akiyama, and Koreaki Ito. Identification and characterization of an escherichia coli gene required for the formation of correctly folded alkaline phosphatase, a periplasmic enzyme. The EMBO Journal, 11:57-62, Jan 1992. URL: https://doi.org/10.1002/j.1460-2075.1992.tb05027.x, doi:10.1002/j.1460-2075.1992.tb05027.x. This article has 366 citations.
(bruna2024anintracellularphosphorusstarvation pages 1-3): Roberto E. Bruna, Christopher G. Kendra, and Mauricio H. Pontes. An intracellular phosphorus-starvation signal activates the phob/phor two-component system in salmonella enterica. Sep 2024. URL: https://doi.org/10.1128/mbio.01642-24, doi:10.1128/mbio.01642-24. This article has 33 citations and is from a domain leading peer-reviewed journal.
(shimizu2013metabolicregulationof pages 19-20): Kazuyuki Shimizu. Metabolic regulation of a bacterial cell system with emphasis on escherichia coli metabolism. ISRN Biochemistry, 2013:1-47, Feb 2013. URL: https://doi.org/10.1155/2013/645983, doi:10.1155/2013/645983. This article has 173 citations.