isoelectric point


Summary: The pH in solutions of proteins and related compounds at which the dipolar ions are at a maximum.

Top Publications

  1. Santiago P, Carvalho F, Domingues M, Carvalho J, Santos N, Tabak M. Isoelectric point determination for Glossoscolex paulistus extracellular hemoglobin: oligomeric stability in acidic pH and relevance to protein-surfactant interactions. Langmuir. 2010;26:9794-801 pubmed publisher
    ..Our focus is on the HbGp stability at acidic pH and also on the determination of the isoelectric point (pI) of the protein...
  2. Alendé N, Nielsen J, Shields D, Khaldi N. Evolution of the isoelectric point of mammalian proteins as a consequence of indels and adaptive evolution. Proteins. 2011;79:1635-48 pubmed publisher
    Although important shifts in the isoelectric point of prokaryotic proteins, mainly due to adaptation to environmental pH, have been widely reported, such studies have not covered mammalian proteins, where pH changes may relate to changes ..
  3. Pihlasalo S, Auranen L, Hanninen P, Harma H. Method for estimation of protein isoelectric point. Anal Chem. 2012;84:8253-8 pubmed publisher the basis of the developed noncompetitive and homogeneous method for the estimation of the protein isoelectric point (pI)...
  4. Grimsley G, Scholtz J, Pace C. A summary of the measured pK values of the ionizable groups in folded proteins. Protein Sci. 2009;18:247-51 pubmed publisher
    ..3 +/- 1.2 (20); Lys 10.5 +/- 1.1 (35); C-terminus 3.3 +/- 0.8 (22) and N-terminus 7.7 +/- 0.5 (16). We compare these results with the measured pK values of these groups in alanine pentapeptides, and comment on our overall findings. ..
  5. Igawa T, Tsunoda H, Tachibana T, Maeda A, Mimoto F, Moriyama C, et al. Reduced elimination of IgG antibodies by engineering the variable region. Protein Eng Des Sel. 2010;23:385-92 pubmed publisher
    ..identical constant regions but different variable region sequences, revealed that an antibody with a lower isoelectric point (pI) has a longer half-life...
  6. Cologna S, Russell W, Lim P, Vigh G, Russell D. Combining isoelectric point-based fractionation, liquid chromatography and mass spectrometry to improve peptide detection and protein identification. J Am Soc Mass Spectrom. 2010;21:1612-9 pubmed publisher a high capacity, high-throughput, mass spectrometry-compatible isoelectric trapping device that provides isoelectric point (pI)-based separations of complex mixtures of peptides...
  7. Muto T, Taniguchi H, Kushima R, Tsuda H, Yonemori H, Chen C, et al. Global expression study in colorectal cancer on proteins with alkaline isoelectric point by two-dimensional difference gel electrophoresis. J Proteomics. 2011;74:858-73 pubmed publisher
    ..IEF/western blotting confirmed the differences in protein expression between the normal and the tumor tissues. These results may provide an insight for biomarker development and drug target discovery in colorectal cancer. ..
  8. Tomita S, Yoshikawa H, Shiraki K. Arginine controls heat-induced cluster-cluster aggregation of lysozyme at around the isoelectric point. Biopolymers. 2011;95:695-701 pubmed publisher
    ..and transmission electron microscopy revealed that heat-induced aggregation of lysozyme at around the isoelectric point occurred in a two-step process: formation of start aggregates, followed by further growth mediated by their ..
  9. Perez Riverol Y, Audain E, Millan A, Ramos Y, Sanchez A, Vizcaino J, et al. Isoelectric point optimization using peptide descriptors and support vector machines. J Proteomics. 2012;75:2269-74 pubmed publisher
    ..Experimental isoelectric point (pI) values can improve peptide identifications in conjunction with MS/MS information...

More Information


  1. Elevi Bardavid R, Oren A. Acid-shifted isoelectric point profiles of the proteins in a hypersaline microbial mat: an adaptation to life at high salt concentrations?. Extremophiles. 2012;16:787-92 pubmed publisher
    ..We here reevaluate these data and conclusions by comparing the isoelectric point profiles of the Guerrero Negro microbial mats (average isoelectric point 6...
  2. Bendtsen J, Nielsen H, von Heijne G, Brunak S. Improved prediction of signal peptides: SignalP 3.0. J Mol Biol. 2004;340:783-95 pubmed publisher
    ..The new method has been benchmarked against other available methods. Predictions can be made at the publicly available web server..
  3. Weiller G, Caraux G, Sylvester N. The modal distribution of protein isoelectric points reflects amino acid properties rather than sequence evolution. Proteomics. 2004;4:943-9 pubmed
    ..a routine application in proteomics, separates proteins according to their molecular mass (M(r)) and isoelectric point (pI)...
  4. Kantardjieff K, Rupp B. Protein isoelectric point as a predictor for increased crystallization screening efficiency. Bioinformatics. 2004;20:2162-8 pubmed
    ..Because pH is one of the few consistently reported parameters in the Protein Data Bank (PDB), the isoelectric point (pI) of a protein has been explored as a useful indirect predictor for the optimal choice of range and ..
  5. Liu H, Zhang R, Yao X, Liu M, Hu Z, Fan B. Prediction of the isoelectric point of an amino acid based on GA-PLS and SVMs. J Chem Inf Comput Sci. 2004;44:161-7 pubmed
    ..for the first time, was used to develop a QSPR model that relates the structures of 35 amino acids to their isoelectric point. Molecular descriptors calculated from the structure alone were used to represent molecular structures...
  6. Uhde Holzem K, Fischer R, Commandeur U. Genetic stability of recombinant potato virus X virus vectors presenting foreign epitopes. Arch Virol. 2007;152:805-11 pubmed
    ..A comparison of the isoelectric point (pI) values and charges of the wild type and rCPs showed that the initial high rCP pI values had changed to ..
  7. Cargile B, Stephenson J. An alternative to tandem mass spectrometry: isoelectric point and accurate mass for the identification of peptides. Anal Chem. 2004;76:267-75 pubmed
    ..This methodology employs the use of accurate mass and peptide isoelectric point (pI) as identification criteria, and represents a change in focus from current tandem mass spectrometry-..
  8. Anderson J, Peck S. A simple and rapid technique for detecting protein phosphorylation using one-dimensional isoelectric focusing gels and immunoblot analysis. Plant J. 2008;55:881-5 pubmed publisher
    ..We demonstrate the application of this method for observing phosphorylation of an Arabidopsis thaliana protein in response to biotic stress. ..
  9. Righetti P. Determination of the isoelectric point of proteins by capillary isoelectric focusing. J Chromatogr A. 2004;1037:491-9 pubmed
    ..Pitfalls and common errors in pI determinations are reviewed here and guidelines given for minimizing such errors in pI estimation. ..
  10. Wang X, Yang H, Ruan L, Liu X, Li F, Xu X. Cloning and characterization of a thermostable superoxide dismutase from the thermophilic bacterium Rhodothermus sp. XMH10. J Ind Microbiol Biotechnol. 2008;35:133-9 pubmed
    ..It also showed much higher resistance to KCN, NaN(3) and H(2)O(2) as compared to other SODs...
  11. Nandi S, Mehra N, Lynn A, Bhattacharya A. Comparison of theoretical proteomes: identification of COGs with conserved and variable pI within the multimodal pI distribution. BMC Genomics. 2005;6:116 pubmed
    ..Orthologs identified that significantly vary between the major acidic and basic regions maybe used as representative of the variation of the entire proteome. ..
  12. Sahab Z, Suh Y, Sang Q. Isoelectric point-based prefractionation of proteins from crude biological samples prior to two-dimensional gel electrophoresis. J Proteome Res. 2005;4:2266-72 pubmed
    ..To take full advantage of IPG strips, the ideal sample should be composed primarily of proteins that have isoelectric point (pI) values within the pH range of the IPG strip...
  13. Sillero A, Maldonado A. Isoelectric point determination of proteins and other macromolecules: oscillating method. Comput Biol Med. 2006;36:157-66 pubmed
    A program written in Visual Basic has been developed to calculate the isoelectric point of proteins and other macromolecules bearing acid-basic residues. The pI value can be theoretically calculated with the precision required...
  14. Valnickova Z, Christensen T, Skottrup P, Thøgersen I, Højrup P, Enghild J. Post-translational modifications of human thrombin-activatable fibrinolysis inhibitor (TAFI): evidence for a large shift in the isoelectric point and reduced solubility upon activation. Biochemistry. 2006;45:1525-35 pubmed
    ..During this study, we observed that (i) the isoelectric point (pI) of TAFI shifts dramatically from pH 5 toward pH 8 upon activation and (ii) TAFIa is significantly less ..
  15. Kiraga J, Mackiewicz P, Mackiewicz D, Kowalczuk M, Biecek P, Polak N, et al. The relationships between the isoelectric point and: length of proteins, taxonomy and ecology of organisms. BMC Genomics. 2007;8:163 pubmed
    The distribution of isoelectric point (pI) of proteins in a proteome is universal for all organisms. It is bimodal dividing the proteome into two sets of acidic and basic proteins...
  16. Liu E, Moriyama H, Abiru N, Paronen J, Devendra D, Finkelman F, et al. Preventing peptide-induced anaphylaxis: addition of C-terminal amino acids to produce a neutral isoelectric point. J Allergy Clin Immunol. 2004;114:607-13 pubmed
    ..We sought to prevent anaphylaxis from B:9-23 peptide by altering the isoelectric point (pI) to neutral, thereby decreasing solubility and rate of absorption after subcutaneous injection...
  17. Guerrero G, Peralta H, Aguilar A, Diaz R, Villalobos M, Medrano Soto A, et al. Evolutionary, structural and functional relationships revealed by comparative analysis of syntenic genes in Rhizobiales. BMC Evol Biol. 2005;5:55 pubmed
    ..In Rhizobiales and Enterobacteriales, syntenic genes encode a high proportion of essential cell functions and presented a high level of functional relationships. ..
  18. Yun Y, Lee Y. Purification and some properties of superoxide dismutase from Deinococcus radiophilus, the UV-resistant bacterium. Extremophiles. 2004;8:237-42 pubmed
    ..The N-terminal peptide sequence of D. radiophilus Mn/FeSOD (MAFELPQLPYAYDALEPHIDA(> D) is strikingly similar to those of D. radiodurans MnSOD and Aerobacter aerogenes FeSOD. ..
  19. Goo Y, Roach J, Glusman G, Baliga N, Deutsch K, Pan M, et al. Low-pass sequencing for microbial comparative genomics. BMC Genomics. 2004;5:3 pubmed
    ..NRC-1 genome as a reference. Low-pass shotgun sequencing is a simple, inexpensive, and rapid approach that can readily be performed on any cultured microbe...
  20. Aslan F, Yu Y, Vajda S, Mohr S, Cantor C. Engineering a novel, stable dimeric streptavidin with lower isoelectric point. J Biotechnol. 2007;128:213-25 pubmed
  21. Danel C, Duval C, Azaroual N, Vaccher C, Bonte J, Bailly C, et al. Complexation of triptolide and its succinate derivative with cyclodextrins: affinity capillary electrophoresis, isothermal titration calorimetry and 1H NMR studies. J Chromatogr A. 2011;1218:8708-14 pubmed publisher
    ..Altogether, the data provide strong evidences that the two triptolide compounds can be efficiently complexed with CD. ..
  22. Gao H, Li C, Ma F, Wang K, Xu J, Chen H, et al. A nanochannel array based device for determination of the isoelectric point of confined proteins. Phys Chem Chem Phys. 2012;14:9460-7 pubmed publisher
    ..charge properties of the immobilized proteins in nanochannel confined conditions, leading us to obtain the isoelectric point (pI) of the proteins confined in nanochannels...
  23. Arroyo Maya I, Rodiles López J, Cornejo Mazón M, Gutiérrez López G, Hernandez Arana A, Toledo Núñez C, et al. Effect of different treatments on the ability of ?-lactalbumin to form nanoparticles. J Dairy Sci. 2012;95:6204-14 pubmed publisher
    ..These nanoparticles, with an isoelectric point of 3.61, are very stable at pH values >4...
  24. Ackermann D, Wang W, Streipert B, Geib B, Grün L, König S. Comparative fluorescence two-dimensional gel electrophoresis using a gel strip sandwich assembly for the simultaneous on-gel generation of a reference protein spot grid. Electrophoresis. 2012;33:1406-10 pubmed publisher
    ..This is an important advancement for projects involving comparison of 2DE-gels produced over several years and in different laboratories. ..
  25. Fung K, Cursaro C, Lewanowitsch T, Cosgrove L, Hoffmann P. A combined free flow electrophoresis and DIGE approach to compare proteins in complex biological samples. Methods Mol Biol. 2012;869:135-46 pubmed publisher
    ..Here we describe an approach combining fluorescent CyDye technology (DIGE) with FFE to simultaneously separate and identify differentially expressed proteins in a model cell system. ..
  26. Adamczyk Z, Bratek Skicki A, Dabrowska P, Nattich Rak M. Mechanisms of fibrinogen adsorption on latex particles determined by zeta potential and AFM measurements. Langmuir. 2012;28:474-85 pubmed publisher
    ..8 (isolectric point) and negative otherwise. However, the latex particles did not show any isoelectric point, remaining strongly negative for this pH range...
  27. Ye M, Chen Z, Zhang T, Shao W. Effect of calcination temperature on the catalytic activity of nanosized TiO(2) for ozonation of trace 4-chloronitrobenzene. Water Sci Technol. 2012;66:479-86 pubmed publisher
    ..However, the isoelectric point (IEP) first increased, and then decreased...
  28. Kim H, Han G, Kim D, Choi J, Kim S. Comparative analysis of two types of methanol dehydrogenase from Methylophaga aminisulfidivorans MPT grown on methanol. J Basic Microbiol. 2012;52:141-9 pubmed publisher
    ..During purification, the lysozyme and freeze-thawing cell disruption method significantly increased the amount of type II MDH in the soluble fraction compared with strong physical disruption methods such as sonication and French Press. ..
  29. Shirley J, Mandale S, Williams P. Amino acid rejection behaviour as a function of concentration. Adv Colloid Interface Sci. 2011;164:118-25 pubmed publisher
    ..At its isoelectric point, lysine was effectively neutral and its behaviour was well described by the model incorporating a steric ..
  30. Sakamoto Y, Nakade K, Sato T. Characterization of the post-harvest changes in gene transcription in the gill of the Lentinula edodes fruiting body. Curr Genet. 2009;55:409-23 pubmed publisher
    ..Transcription of L. edodes exp1 increased post-harvest, which suggests that its target genes are up-regulated after harvesting. These enzymes and the transcription factor may be involved in L. edodes fruiting body senescence. ..
  31. Chi Z, Wang X, Geng Q, Chi Z. Role of a GATA-type transcriptional repressor Sre1 in regulation of siderophore biosynthesis in the marine-derived Aureobasidium pullulans HN6.2. Biometals. 2013;26:955-67 pubmed publisher
    ..An open reading frame (ORF) of 1,002 bp encoding a 334 amino acid protein (a calculated isoelectric point: 8.6) with a calculated molecular weight of 35.1 kDa was characterized...
  32. Ly L, Wasinger V. Mass and charge selective protein fractionation for the differential analysis of T-cell and CD34+ stem cell proteins from cord blood. J Proteomics. 2010;73:571-8 pubmed publisher
  33. Miller I, Eberini I, Gianazza E. Other than IPG-DALT: 2-DE variants. Proteomics. 2010;10:586-610 pubmed publisher
    ..Electrophoresis is then performed either in first dimension or in both first dimension and second dimension under non-denaturing (native) and/or non-reducing conditions. ..
  34. Takakura Y, Oka N, Kajiwara H, Tsunashima M. Engineering of novel tamavidin 2 muteins with lowered isoelectric points and lowered non-specific binding properties. J Biosci Bioeng. 2012;114:485-9 pubmed publisher
    ..The isoelectric point of tamavidin 2 is 7.4-7.5, lower than avidin (10.0), and slightly higher than that of streptavidin (6.0-7.5)...
  35. Xu M, Zhao Y, Feng M. Polyaspartamide derivative nanoparticles with tunable surface charge achieve highly efficient cellular uptake and low cytotoxicity. Langmuir. 2012;28:11310-8 pubmed publisher
    ..Therefore, the zwitterionic PASP-pg-TEPA nanoparticles could overcome limitations of cationic nanocarriers and achieve efficient intracellular delivery with low cytotoxicity. ..
  36. Schmidt G, Krings U, Nimtz M, Berger R. A surfactant tolerant laccase of Meripilus giganteus. World J Microbiol Biotechnol. 2012;28:1623-32 pubmed publisher
    ..The enzyme possessed an isoelectric point of 3...
  37. Wang N, Yan X, Gao X, Niu H, Kang Z, Huang L. Purification and characterization of a potential antifungal protein from Bacillus subtilis E1R-J against Valsa mali. World J Microbiol Biotechnol. 2016;32:63 pubmed publisher
    ..44 kDa and isoelectric point of 9.94...
  38. Li C, Mezzenga R. Functionalization of multiwalled carbon nanotubes and their pH-responsive hydrogels with amyloid fibrils. Langmuir. 2012;28:10142-6 pubmed publisher
    ..The presence of the isoelectric point of amyloid fibrils allows a reversible gelling behavior through ionic interactions with functionalized MWNTs. ..
  39. Lu Y, Kong H, Wen F, Zhang S, Zhang X. Lab-on-graphene: graphene oxide as a triple-channel sensing device for protein discrimination. Chem Commun (Camb). 2013;49:81-3 pubmed publisher
    ..Based on the phenomenon, a triple-channel optical sensor has been proposed in the present communication for protein discrimination with GO as a single sensing element. ..
  40. Hwang S, Kim H, Choo J, Seong G, Hien T, Lee E. Effects of operating parameters on the efficiency of liposomal encapsulation of enzymes. Colloids Surf B Biointerfaces. 2012;94:296-303 pubmed publisher
    ..This approach can be used to optimize the liposomal encapsulation of clinically significant proteins. ..
  41. Liu H, Surawanvijit S, Rallo R, Orkoulas G, Cohen Y. Analysis of nanoparticle agglomeration in aqueous suspensions via constant-number Monte Carlo simulation. Environ Sci Technol. 2011;45:9284-92 pubmed publisher
    ..that nanoparticle agglomerate size increased both with ionic strength and as the solution pH approached the isoelectric point (IEP)...
  42. Bansch P, Nelson A, Ohlsson T, Bentzer P. Effect of charge on microvascular permeability in early experimental sepsis in the rat. Microvasc Res. 2011;82:339-45 pubmed publisher
    ..escape rate (TER) and initial distribution volume for (125)I-labeled bovine serum albumin (BSA, isoelectric point pH 4.6) and for (131)I-labeled charge modified BSA (cBSA, average isoelectric point, pH 7...
  43. Normand J, Ralet M, Thibault J, Rogniaux H, Delavault P, Bonnin E. Purification, characterization, and mode of action of a rhamnogalacturonan hydrolase from Irpex lacteus, tolerant to an acetylated substrate. Appl Microbiol Biotechnol. 2010;86:577-88 pubmed publisher
    ..Oligomers esterified by an acetyl group on the reducing galacturonic acid residue or fully acetylated were detected in the hydrolysate showing that the novel enzyme is able to bind acetylated galacturonic acid in its active site...
  44. Zhang X, Zhang M, Zheng C, Liu J, Hu H. Identification of two hsp90 genes from the marine crab, Portunus trituberculatus and their specific expression profiles under different environmental conditions. Comp Biochem Physiol C Toxicol Pharmacol. 2009;150:465-73 pubmed publisher
    ..These results suggested there were at least two Hsp90s in P. trituberculatus, which played differing roles in physiological and stressful conditions. ..
  45. Manconi B, Messana I, Maggiani F, Olianas A, Pellegrini M, Crnjar R, et al. Structural and functional characterization of Delphinus delphis hemoglobin system. J Comp Physiol B. 2009;179:971-83 pubmed publisher
    ..Regarding the particularly lowered cooperativity of HbII, it is interesting to observe that the variant human HbA, characterized by the substitution Lysbeta65 --> Gln (HbJ-Cairo) has a decreased cooperativity with respect to HbA(0). ..
  46. Yuan G, Wang Y, Gluhak Heinrich J, Yang G, Chen L, Li T, et al. Tissue-specific expression of dentin sialophosphoprotein (DSPP) and its polymorphisms in mouse tissues. Cell Biol Int. 2009;33:816-29 pubmed publisher
    ..The predicted secondary structure of DPP domain of this DSPP showed differences from the previously published mouse DPPs, implying that they play different roles during tooth development and formation. ..
  47. Santos M, Gangoiti J, Keul H, Möller M, Serra J, Llama M. Polyester hydrolytic and synthetic activity catalyzed by the medium-chain-length poly(3-hydroxyalkanoate) depolymerase from Streptomyces venezuelae SO1. Appl Microbiol Biotechnol. 2013;97:211-22 pubmed publisher
  48. Dixit N, Maloney K, Kalonia D. Application of quartz crystal microbalance to study the impact of pH and ionic strength on protein-silicone oil interactions. Int J Pharm. 2011;412:20-7 pubmed publisher
    ..0 to 9.0, and at ionic strengths of 10 mM and 150 mM. At low ionic strength (10mM) and pH 5.0 (close to the isoelectric point of the protein), maximum adsorption of protein to the silicone oil surface was observed...
  49. Sakthivel M, Geraldine P, Thomas P. Alterations in the lenticular protein profile in experimental selenite-induced cataractogenesis and prevention by ellagic acid. Graefes Arch Clin Exp Ophthalmol. 2011;249:1201-10 pubmed publisher
    ..This study aimed to evaluate whether ellagic acid, a natural polyphenol with antioxidant properties, prevents alterations in the lenticular protein profile in an experimental model of selenite cataract...
  50. Zochowska M. [Possibility of practical application of U-Tube and D-Tube for proteins concentration]. Postepy Biochem. 2010;56:95-7 pubmed
    ..Therefore, they are effective tools for proteins concentration, especially these proteins that tend to bind to the membrane. ..
  51. Zhang Y, Zheng T, Wang Y, Guo Y, Ding F, Fei M, et al. Production of biologically active recombinant annexin B1 with enhanced stability via a tagging system. Appl Microbiol Biotechnol. 2010;85:605-14 pubmed publisher
  52. Wang X, Liu L, Luo Y, Shi H, Li J, Zhao H. Comb-shaped glycopolymer/peptide bioconjugates by combination of RAFT polymerization and thiol-ene "click" chemistry. Macromol Biosci. 2012;12:1575-82 pubmed publisher
    ..The size of micelles decreases with increasing pH, demonstrating pH-responsive character. The isoelectric point (IEP) of the PMAGlc/GSH bioconjugate is estimated to be 3.43...
  53. Deiber J, Piaggio M, Peirotti M. Determination of electrokinetic and hydrodynamic parameters of proteins by modeling their electrophoretic mobilities through the electrically charged spherical soft particle. Electrophoresis. 2013;34:708-15 pubmed publisher
    ..the protein charge regulation phenomenon and the SSP particle core are included to study BSA having isoelectric point pI ? 5.71, within a wide range of bulk pH values...