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At least 19 recordsLinked to original sources

PubMed1999

A new type sandwich immunoassay for microcystin: production of monoclonal antibodies specific to the immune complex formed by microcystin and an anti-microcystin monoclonal antibody.

To develop an ultrasensitive immunoassay for microcystins (MCs), a group of heptapeptide hepatotoxins produced by cyanobacteria, we produced monoclonal antibodies (MAbs) which specifically recognize the immune complex (IC) formed by an anti-MC MAb (MC MAb) and MCs. The use of the anti-IC MAb (IC MAb) as the secondary antibody made it possible to develop a sandwich type immunoassay, which is theoretically superior to the widely used competitive immunoassay in sensitivity as well as accuracy. A MC MAb mixed with microcystin-LR (MCLR) to form the IC was immunized to mice. Three IC MAbs were obtained, all of which specifically reacted with the IC, but almost never reacted to MC MAb or MCLR in enzyme-linked immunosorbent assays (ELISAs). Binding kinetics study of one of the IC MAbs, 3F7, by a BIAcore biosensor technique revealed that 3F7 IC MAb could associate with free MC MAb as well as the IC, but the binding to free MC MAb was much more easily dissociated than that to the IC, thus resulting in about 300-fold higher affinity of 3F7 for the IC than for MC MAb alone (1.8 x 10(9) M(-1) and 4.6 x 10(6) M(-1) for the IC and MC MAb, respectively). Finally, 3F7 IC MAb was shown to react with the IC formed by the addition of MCLR to MC MAb-coated plates in a dose-dependent manner. Therefore, a new type sandwich immunoassay, anti-immune complex ELISA (IC ELISA) for MCs, was indeed established. The detection limit of the IC ELISA was 2 pg of MCLR ml(-1) (50 fg per assay), making it the most sensitive of all the methods for detecting MCs reported to date.

Animals↗

PubMed2001

High grazer toxicity of [D-Asp(3),(E)-Dhb(7)]microcystin-RR of Planktothrix rubescens as compared to different microcystins.

Planktothrix rubescens, the dominant cyanobacterium in Lake Zürich, is generally considered to be toxic to zooplankton. The major toxin was determined by NMR spectroscopy and chemical analysis to be [D-Asp(3),(E)-Dhb(7)]microcystin-RR. The compound was isolated in high purity, and its 24-h acute grazer toxicity was compared with microcystin-LR, microcystin-RR, microcystin-YR, and nodularin using a Thamnocephalus platyurus bioassay. Based on LC(50) values [D-Asp(3),(E)-Dhb(7)]microcystin-RR was the most toxic microcystin tested. Nodularin was slightly more toxic under the conditions of the assay. The large number of individuals available for the grazer bioassay allowed the determination of dose-response curves of the different microcystins. These curves showed marked differences in their steepness. Microcystin-RR, which had nearly the same LC(50) as microcystin-LR and microcystin-YR, exhibited a very flat dose-response curve. This flat curve indicates that, for some individuals, lower concentrations of this microcystin are much more toxic than are the other two microcystins. Mortality of 100% requires much higher concentrations of microcystin-RR, indicating the resistance of some animals to the toxin. The purified [D-Asp(3),(E)-Dhb(7)]microcystin-RR exhibited a higher molar absorption coefficient determined by quantitative amino acid analysis than the coefficients generally used for other microcystins. This observation has consequences for the risk assessment for microcystins and makes a structural determination of microcystins an absolute requirement. The presence of the dehydrobutyrine residue may be the reason for the higher specific toxicity of [D-Asp(3),(E)-Dhb(7)]microcystin-RR when compared to the N-methyldehydroalanine-containing microcystins.

Animals↗

PubMed2003

The abundance of microcystin-producing genotypes correlates positively with colony size in Microcystis sp. and determines its microcystin net production in Lake Wannsee.

The working hypotheses tested on a natural population of Microcystis sp. in Lake Wannsee (Berlin, Germany) were that (i) the varying abundance of microcystin-producing genotypes versus non-microcystin-producing genotypes is a key factor for microcystin net production and (ii) the occurrence of a gene for microcystin net production is related to colony morphology, particularly colony size. To test these hypotheses, samples were fractionated by colony size with a sieving procedure during the summer of 2000. Each colony size class was analyzed for cell numbers, the proportion of microcystin-producing genotypes, and microcystin concentrations. The smallest size class of Microcystis colonies (<50 microm) showed the lowest proportion of microcystin-producing genotypes, the highest proportion of non-microcystin-producing cells, and the lowest microcystin cell quotas (sum of microcystins RR, YR, LR, and WR). In contrast, the larger size classes of Microcystis colonies (>100 microm) showed the highest proportion of microcystin-producing genotypes, the lowest proportion of non-microcystin-producing cells, and the highest microcystin cell quotas. The microcystin net production rate was nearly one to one positively related to the population growth rate for the larger colony size classes (>100 microm); however, no relationship could be found for the smaller size classes. It was concluded that the variations found in microcystin net production between colony size classes are chiefly due to differences in genotype composition and that the microcystin net production in the lake is mainly influenced by the abundance of the larger (>100- microm) microcystin-producing colonies.

Bacterial Proteins↗

PubMed1997

Bioaccumulation and clearance of microcystins from salt water mussels, Mytilus edulis, and in vivo evidence for covalently bound microcystins in mussel tissues.

Over a period of 3 days saltwater mussels, Mytilus edulis, were fed a cyanobacteria, Microcystis aeruginosa, that contained a high concentration of microcystins. The mussels were killed on a periodic basis over the course of 2 months. Mussels were also collected at two sites were high levels of microcystins in tissues had been noted. A strategy based on the chemically unique nature of the C20 beta-amino acid, (2S,3S,8S,9S)-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6- dienoic acid (Adda), portion of the microcystins was used in conjunction with a protein phosphatase (PPase) assay to analyse for both covalently bound microcystins and free microcystins in the mussel tissues. The mussel PPase assay results were compared with the Lemieux oxidation gas chromatography-mass spectrometry (GCMS) analysis. Less than 0.1% of the total microcystin burden in the mussel tissue was found to be extractable with MeOH. Thus, direct evidence was provided for the existence of covalently bound microcystins in mussel tissues in vivo. The mussels rapidly cleared the covalently bound microcystins when transferred to untreated seawater. Within 4 days the total microcystin burden dropped from a high of 336.9 (+/- 45.8) micrograms/g wet tissue to 11.3 (+/- 2.6) micrograms/g. After 4 days postexposure until completion of the experiment the total levels remained below the detection limits of the GCMS method. The levels of free microcystins, extracted with MeOH and detected by the PPase assay, fell from 204 ng/g wet tissue to a residual 14 ng/g over a 53 day postexposure period. Presumably the bound microcystin present in the mussel tissue exists as a covalent complex with the PP-1 and PP-2A enzymes. We conclude that in any shellfish monitoring program it is the total tissue microcystin burden that needs to be considered.

Animals↗

PubMed2002

Rapid isolation of a single-chain antibody against the cyanobacterial toxin microcystin-LR by phage display and its use in the immunoaffinity concentration of microcystins from water.

A naïve (unimmunized) human semisynthetic phage display library was employed to isolate recombinant antibody fragments against the cyanobacterial hepatotoxin microcystin-LR. Selected antibody scFv genes were cloned into a soluble expression vector and expressed in Escherichia coli for characterization against purified microcystin-LR by competition enzyme-linked immunosorbent assay (ELISA). The most sensitive single-chain antibody (scAb) isolated was capable of detecting microcystin-LR at levels below the World Health Organization limit in drinking water (1 microg liter(-1)) and cross-reacted with three other purified microcystin variants (microcystin-RR, -LW, and -LF) and the related cyanotoxin nodularin. Extracts of the cyanobacterium Microcystis aeruginosa were assayed by ELISA, and quantifications of microcystins in toxic samples showed good correlation with analysis by high-performance liquid chromatography. Immobilized scAb was also used to prepare immunoaffinity columns, which were assessed for the ability to concentrate microcystin-LR from water for subsequent analysis by high-performance liquid chromatography. Anti-microcystin-LR scAb was immobilized on columns via a hexahistidine tag, ensuring maximum exposure of antigen binding sites, and the performance of the columns was evaluated by directly applying 150 ml of distilled water spiked with 4 micro g of purified microcystin-LR. The procedure was simple, and a recovery rate of 94% was achieved following elution in 1 ml of 100% methanol. Large-scale, low-cost production of anti-microcystin-LR scAb in E. coli is an exciting prospect for the development of biosensors and on-line monitoring systems for microcystins and will also facilitate a range of immunoaffinity applications for the cleanup and concentration of these toxins from environmental samples.

Cross Reactions↗

PubMed2002

[ADMAdda5]-microcystins in Planktothrix agardhii strain PH-123 (cyanobacteria)--importance for monitoring of microcystins in the environment.

Two major and two minor microcystins (MCYST) were isolated from a hepatotoxic Danish strain of Planktothrix agardhii (Gomont) Anagnostidis et Komárek by reversed-phase high-performance liquid chromatography. The microcystins were characterized by UV spectroscopy, amino acid analysis, fast atom bombardment mass spectrometry (FABMS), and high-resolution FABMS. The major microcystins were further analysed by collisionally induced tandem electrospray ionization MS. The microcystins were found to be demethylated variants of MCYST-HtyR (homotyrosine-arginine) and MCYST-LR (leucine-arginine). The two major microcystins contained an acetyl-demethyl variant (ADMAdda) of 3-amino-9-acetoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid (Adda). This is the first report of [ADMAdda5]-microcystins in Planktothrix. The two [ADMAdda5]-microcystins inhibited protein phosphatase activity but showed low cross-reactivity with antibodies of an enzyme-linked immunosorbent assay (ELISA), emphasizing the potential underestimation of the toxicity of natural blooms dominated by Planktothrix when microcystin content is quantified using only an ELISA.

Chromatography, High Pressure Liquid↗

PubMed2002

An international intercomparison exercise for the determination of purified microcystin-LR and microcystins in cyanobacterial field material.

The comparability of current microcystin analysis methods has been evaluated in an international intercomparison exercise. The focus was on the analysis of microcystins by high-performance liquid chromatography coupled with ultraviolet or photodiode-array detection (HPLC-PDA/UV), currently the most widespread method for microcystin analysis, but the exercise was open for other methods such as enzyme-linked immunosorbent assay (ELISA), protein phosphatase inhibition assay (PPA) and high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS).Thirty-one laboratories from 13 countries participated in the study. For a microcystin-LR (MC-LR) standard solution (S1) of undisclosed quantity, and for a field sample (S3) from a natural cyanobacterial bloom, repeatabilities between 4 and 15% and reproducibilities between 24 and 49% were obtained. No significant differences between single methods were found for S1 and S3, except for a significantly higher repeatability value of ELISA for S1. However, the analysis of microcystins in the field sample (S3) by HPLC-PDA/UV was significantly more variable than for the standard solution (S1). Both the extraction and the analysis of the microcystins appeared to contribute to this variability. It is concluded that standard MC-LR (S1) can be measured with adequate precision by all participating laboratories independently of the method used. With respect to the different methods used the results for the field sample can also be regarded as satisfactory, but clearly showed the need for improvement by standardisation between laboratories. Furthermore, quantification with in-house standards compared to quantification using the supplied MC-LR standard indicated that routine microcystin analysis in laboratories may be also influenced by the variability of available standards, emphasising the need for the production of certified reference materials (CRM).

Chromatography, High Pressure Liquid↗

PubMed2001

[D-Leu(1)] microcystin-LR, a new microcystin isoplated from waterbloom in a Canadian prairie lake.

A previously undescribed cyclic heptapeptide hepatotoxin was isolated from a cyanobacteria waterbloom collected in Pakowki Lake, Alberta, Canada (49 degrees 20'N and 110 degrees 55'W). The compound was characterized by amino acid analysis, ESIMS/CID/MS, (1)H and (13)C NMR, and UV spectroscopy. Structure of the new microcystin was assigned as [D-Leu(1)]microcystin-LR (1). The amino acid composition is the same as microcystin-LR (2) except for D-Leu and L-Leu in 1 instead of D-Ala and L-Leu in 2. This is the first microcystin identified, among the 64 known microcystins, that has both a D- and L-Leu amino acid. Toxicity as measured by the protein phosphatase inhibition activity of 1 is similar to microcystin-LR. The presence of microcystins in waterblooms from this lake is discussed in relation to the almost yearly bird mortalities that have occurred there since 1995.

Chromatography, High Pressure Liquid↗

PubMed1993

Isolation and identification of eight microcystins from thirteen Oscillatoria agardhii strains and structure of a new microcystin.

Microcystins (cyclic heptapeptide hepatotoxins), isolated from 13 freshwater Oscillatoria agardhii strains from eight different Finnish lakes by high-performance liquid chromatography, were characterized by amino acid analysis, fast atom bombardment mass spectrometry (FABMS), and tandem FABMS (FABMS/collisionary-induced dissociation/MS). All strains produced two to five different microcystins. In total, eight different compounds, of which five were known microcystins, were isolated. The known compounds identified were [D-Asp3]MCYST (microcystin)-LR, [Dha7]MCYST-LR, [D-Asp3]MCYST-RR, [Dha7]MCYST-RR, and [D-Asp3,Dha7]MCYST-RR. This is the first time that isolation of these toxins from Oscillatoria spp., with the exception of [D-Asp3]MCYST-RR, has been reported. Three of the strains produced a new microcystin, and the structure was assigned as [D-Asp3,Mser7]MCYST-RR. The structures of two new microcystins, produced as minor components by one Oscillatoria strain, could not be determined because of the small amounts isolated from the cells. Four strains produced [Dha7]MCYST-RR as the main toxin, but [D-Asp3]MCYST-RR was clearly the most abundant and most frequently occurring toxin among these isolates of O. agardhii.

Amino Acid Sequence↗

PubMed2003

Life-history characteristics of Daphnia exposed to dissolved microcystin-LR and to the cyanobacterium Microcystis aeruginosa with and without microcystins.

In the current study, the role of microcystin(MC)-LR in inhibiting Daphnia growth was examined. Somatic growth, time to first reproduction, number of newborns, mortality, and population growth were measured in Daphnia fed mixtures of the cyanobacterium Microcystis aeruginosa (with and without microcystin) with a high quality green algal food (Scenedesmus obliquus) to avoid nutritional deficiency. Microcystin-LR-containing cells caused a dramatic reduction in growth and resulted in death of the animals, but the addition of purified toxin (microcystin-LR) had no effect on Daphnia growth. In contrast with the nutritional inadequacy hypothesis, growth on a mixture of Scenedesmus and the microcystin-free food was significantly reduced. This observation could not be explained from morphological characteristics of the strains that were uni- and bicellular. Clearance rates of Daphnia fed mixtures of Microcystis and Scenedesmus were significantly lower than rates of animals fed solely Scenedesmus. The results of an additional life-history experiment with different quantities of Scenedesmus could not reject the hypothesis that reduced feeding may be the causal factor in explaining reduced Daphnia growth on the food mixture with microcystin-free Microcystis. Thus, feeding inhibition should be considered in explaining the food quality of Microcystis and other cyanobacteria, as it could affect the total food intake and consequently Daphnia growth.

Analysis of Variance↗

PubMed1998

The solution NMR structure of a blue-green algae hepatotoxin, microcystin-RR--a comparison with the structure of microcystin-LR.

The microcystin-RR structures are compared with the structures of microcystin-LR in solution as well as in the crystal structure of the complex with protein phosphatase. The gross structures of the two peptides are similar, but with a more accentuated and compact saddle structure for microcystin-RR. The structural differences affect the hydrogen-bond pattern in the peptides and the location of the side chain of N-methyldehydroalanine, both of which are important for the ability of the peptide to form a tight complex with protein phosphatase. These structural differences may contribute to the observed differences in toxicity of microcystin-RR and microcystin-LR.

Cyanobacteria↗

PubMed2003

Effects of microcystin-free and microcystin-containing strains of the cyanobacterium Microcystis aeruginosa on growth of the grazer Daphnia magna.

Harmful effects of the common bloom-forming cyanobacterium Microcystis aeruginosa on the grazer Daphnia have been explained from morphological features, nutritional insufficiency, and the production of toxins called microcystins. The effects of four M. aeruginosa strains, including one free of microcystins, on the growth of Daphnia magna were examined. Population growth was measured in Daphnia fed each M. aeruginosa strain alone and fed mixtures of each strain with the green alga Scenedesmus obliquus to avoid nutritional deficiency. The presence of Microcystis in the food resulted in decreased Daphnia population growth rates. A significant correlation (P < 0.001) was found between the amount of microcystins (MC) in the food and the population growth rate, but growth inhibition in Daphnia fed with the MC-free strain could not be explained by the toxicity of the microcystins. Inasmuch as there was greater reduction in growth of the Daphnia fed mixtures of the MC-free strain with Scenedesmus than of the Daphnia fed only the same amount of Scenedesmus as in the mixtures, other factors associated with this Microcystis strain must have inhibited growth. However, morphology and nutritional insufficiency could be excluded as causal factors. The strong relationship between Daphnia feeding activity and population growth suggests that feeding inhibition may have caused the observed detrimental effects on the animals.

Animals↗

PubMed2003

Natural variation in the microcystin synthetase operon mcyABC and impact on microcystin production in Microcystis strains.

Toxic Microcystis strains often produce several isoforms of the cyclic hepatotoxin microcystin, and more than 65 isoforms are known. This has been attributed to relaxed substrate specificity of the adenylation domain. Our results show that in addition to this, variability is also caused by genetic variation in the microcystin synthetase genes. Genetic characterization of a region of the adenylation domain in module mcyB1 resulted in identification of two groups of genetic variants in closely related Microcystis strains. Sequence analyses suggested that the genetic variation is due to recombination events between mcyB1 and the corresponding domains in mcyC. Each variant could be correlated to a particular microcystin isoform profile, as identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry. Among the Microcystis species studied, we found 11 strains containing different variants of the mcyABC gene cluster and 7 strains lacking the genes. Furthermore, there is no concordance between the phylogenies generated with mcyB1, 16S ribosomal DNA, and DNA fingerprinting. Collectively, these results suggest that recombination between imperfect repeats, gene loss, and horizontal gene transfer can explain the distribution and variation within the mcyABC operon.

Amino Acid Sequence↗

PubMed1997

14C-labeled microcystin-LR administered to Atlantic salmon via intraperitoneal injection provides in vivo evidence for covalent binding of microcystin-LR in salmon livers.

The tissue distribution and clearance of radiolabeled microcystin-LR administered to Atlantic salmon via i.p. injection has been re-examined using uniformly 14C-labeled toxin. Significant differences were found to exist between these results and those obtained when fish received an i.p. injection of tritium-labeled dihydromicrocystin-LR. In addition, MeOH liver extracts were assayed by both phosphatase assay and 14C counts and the results compared with the total levels of incorporation determined by digestion and subsequent 14C counting of the same live tissues. An attempt to investigate the metabolism and to document the putative products was also undertaken. It was found that microcystin-LR was extensively metabolized to compounds that are more polar than the parent compound.

Animals↗

PubMedDate not supplied

Immunohistochemical localization of microcystin-LR in the liver of mice: a study on the pathogenesis of microcystin-LR-induced hepatotoxicity.

The relationship between the intralobular sites of hepatotoxic injury and the distribution of microcystin-LR (MCLR), an inhibitor of protein phosphatases 1 (PP1) and 2A (PP2A), was examined using an immunohistochemical method with a monoclonal antibody specific to MCLR on the livers of mice receiving a single i.p. injection of the MCLR. Immunoblotting and high-performance liquid chromatography analyses of liver extracts were also performed to determine the binding form of MCLR to PP1 and PP2A (MCLR-PP1/PP2A adducts) and free MCLR. Immunohistochemistry revealed a discernible intensity of staining in the centrilobular regions where hemorrhage and apoptosis occurred. In these regions, immunopositivity was evident in the cytoplasm and nuclei of the hepatocytes; some apoptotic cells were also immunopositive. In contrast, coagulative necrosis, which was mainly evident in the midlobular regions, was completely negative. Analysis of liver extracts demonstrated MCLR-PP1/PP2A adducts, but free MCLR was below detection limit. These results suggest that the immunohistochemical localization of MCLR in centrilobular hepatocytes is closely associated with the onset of hemorrhage and apoptosis and is related to adduct formation. The occurrence of coagulative necrosis however might also be related to other factors such as ischemia/hypoxia.

Animals↗

PubMed2001

Effects of cell-bound microcystins on survival and feeding of Daphnia spp.

The influence of cell-bound microcystins on the survival time and feeding rates of six Daphnia clones belonging to five common species was studied. To do this, the effects of the microcystin-producing Microcystis strain PCC7806 and its mutant, which has been genetically engineered to knock out microcystin synthesis, were compared. Additionally, the relationship between microcystin ingestion rate by the Daphnia clones and Daphnia survival time was analyzed. Microcystins ingested with Microcystis cells were poisonous to all Daphnia clones tested. The median survival time of the animals was closely correlated to their microcystin ingestion rate. It was therefore suggested that differences in survival among Daphnia clones were due to variations in microcystin intake rather than due to differences in susceptibility to the toxins. The correlation between median survival time and microcystin ingestion rate could be described by a reciprocal power function. Feeding experiments showed that, independent of the occurrence of microcystins, cells of wild-type PCC7806 and its mutant are able to inhibit the feeding activity of Daphnia. Both variants of PCC7806 were thus ingested at low rates. In summary, our findings strongly suggest that (i) sensitivity to the toxic effect of cell-bound microcystins is typical for Daphnia spp., (ii) Daphnia spp. and clones may have a comparable sensitivity to microcystins ingested with food particles, (iii) Daphnia spp. may be unable to distinguish between microcystin-producing and -lacking cells, and (iv) the strength of the toxic effect can be predicted from the microcystin ingestion rate of the animals.

Animals↗

PubMed1995

Isolation and characterization of microcystins from laboratory cultures and environmental samples of Microcystis aeruginosa and from an associated animal toxicosis.

Six microcystins were identified in a laboratory culture of the cyanobacterium (blue-green alga) Microcystis aeruginosa PCC 7813 using high-performance liquid chromatography coupled with diode array detection (HPLC-DAD) and mass spectrometry (LC-MS). The toxins were purified and further characterized by amino acid analysis and tandem mass spectrometry (MS-MS). The presence of the previously reported microcystin-LR and microcystin-LY was confirmed. Two further microcystins were characterized as microcystin-LW and microcystin-LF. Another two toxins were partially characterized and are believed to be an analog of microcystin-LR (molecular weight 1008) and microcystin-LM (molecular weight 969). Natural bloom material of M. aeruginosa collected from 2 reservoirs was found to have similar microcystin profiles using HPLC-DAD and LC-MS, indicating the widespread occurrence of these microcystin variants. In addition, the presence of 5 of the microcystins was confirmed in the rumen contents of a lamb by LC-MS and LC-MS-MS, providing the first report of microcystins identified in an animal suspected of being poisoned by cyanobacterial hepatotoxins.

Amino Acid Sequence↗

PubMed2001

Diversity of microcystin genes within a population of the toxic cyanobacterium Microcystis spp. in Lake Wannsee (Berlin, Germany).

In order to find out how many genotypes determine microcystin production of Microcystis spp. in field populations, single colonies (clones) were sampled from Lake Wannsee (Berlin, Germany), characterized morphologically, and subsequently analyzed by PCR for a region within the mcyB gene encoding the activation of one amino acid during microcystin biosynthesis. The different morphospecies varied considerably in the proportion of microcystin-producing genotypes. Most colonies (73%) of M. aeruginosa contained this gene whereas only 16% of the colonies assigned to M. ichthyoblabe and no colonies of M. wesenbergii gave a PCR product of the mcyB gene. Restriction fragment length polymorphism revealed seven restriction profiles showing low variability in nucleotide sequence within each restriction type (0.4-4%) and a low to high variability (1.6-38%) between restriction types. In addition, the sequences of amino acids within the mcyB gene were analyzed to compare the specificity of the amino acid activation during microcystin biosynthesis between restriction types and with the occurrence of amino acids in microcystin variants as detected by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Most of the microcystin-producing colonies showed high similarity in the sequence of amino acids and contained microcystin-LR (LR refers to leucine and arginine in the variable positions of the heptapeptide), microcystin-RR, and microcystin-YR, as well as other variants in minor concentrations. It is concluded that the gene product found for most of the microcystin-producing colonies in the lake is rather unspecific and the diversity of microcystin variants in the lake results from activation of various amino acids during microcystin biosynthesis in the same genotypes.

Amino Acid Sequence↗