Methyl Red Indicator
Methyl Red Indicator - Related Videos
02:39
Indicators
0 Views •
2020
Certain organic substances change color in dilute solution when the hydronium ion concentration reaches a particular value. For example, phenolphthalein is a colorless substance in any aqueous solution with a hydronium ion concentration greater than 5.0 × 10−9 M (pH < 8.3). In more basic solutions where the hydronium ion concentration is less than 5.0 × 10−9 M (pH > 8.3), it is red or pink. Substances such as phenolphthalein, which can be used to determine the pH of a solution, are called...
08:17
Water Quality Analysis via Indicator Organisms
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2023
Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba -The University of Arizona Demonstrating Author: Luisa Ikner Water quality analysis monitors anthropogenic influences such as pollutants, nutrients, pathogens, and any other constituent that can impact the water’s integrity as a resource. Fecal contamination contributes microbial pathogens that threaten plant, animal, and human health with disease or illness. Increasing water demands and strict quality standards require that water...
08:47
DNA Methylation Analysis
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Methylation at CpG dinucleotides is a chemical modification of DNA hypothesized to play important roles in regulating gene expression. In particular, the methylation of clusters of methylation sites, called “CpG islands”, near promoters and other gene regulatory elements may contribute to the stable silencing of genes, for example, during epigenetic processes such as genomic imprinting and X-chromosome inactivation. At the same time, aberrant CpG methylation has been shown to be associated with...
12:34
DNA Methylation: Bisulphite Modification and Analysis
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Cited by 75 •
2011
The gold standard for DNA methylation analysis is genomic sequencing of bisulphite converted DNA. This method takes advantage of the increased sensitivity of cytosine compared with 5-methylcytosine (5-MeC) to bisulphite deamination under acidic conditions. Unmethylated cytosines can be distinguished from methylated cytosines after PCR amplification of the target genomic DNA.
21:24
Methylated DNA Immunoprecipitation
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Cited by 43 •
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This video demonstrates the protocol for methylated DNA immunoprecipitation (MeDIP). MeDIP is a two day procedure that selectively extracts methylated DNA fragments from a genomic DNA sample using antibodies with specificity for 5 -methylcytosine (anti-5 mC).
FAQs
Methyl red behaves as a weak acid whose molecular structure changes when it gains or loses a proton. Those protonation-dependent structural forms interact differently with visible light, producing the observed color shift. Consequently, the indicator does not respond simply as a binary signal; its color reflects the balance between protonated and deprotonated forms in the solution.
Orange appears when both protonated and deprotonated forms are present in appreciable amounts during the indicator’s transition. This mixed state occurs between the strongly acidic red region below approximately pH 4.4 and the yellow region above about pH 6.2. The intermediate color therefore signals a changing acidity rather than a single sharply defined pH.
The transition range shows that methyl red is most informative when the solution’s pH moves through approximately 4.4 to 6.2. Red indicates conditions below this interval, yellow indicates conditions above it, and orange suggests an intermediate value. Interpreting the color as a range helps avoid treating the indicator as an exact pH measurement.
In an acid-base titration, the indicator is used to reveal when the solution enters its characteristic color-transition interval. Observing the change from red through orange toward yellow helps identify an endpoint range associated with changing acidity. This visual response is useful when the titration’s relevant endpoint falls within the indicator’s approximately pH 4.4 to 6.2 transition range.
The methyl red test uses the indicator to detect stable mixed-acid fermentation. A result showing the relevant acidic condition provides evidence that a bacterial culture followed this metabolic pathway. Because different bacteria can use different fermentation pathways, the test helps distinguish organisms according to the metabolic products and acidity associated with their growth.
Its microbiological application is especially useful when the goal is to distinguish bacterial metabolic pathways rather than merely observe a solution’s acidity. In that setting, the indicator contributes to a methyl red test for stable mixed-acid fermentation. In chemistry, the same color response instead supports acid-base observations, including transition and endpoint-range monitoring.