Acids have a pH from 0-7, while bases have a pH from 7-14. A pH of exactly 7.0 is neutral, indicating that a substance is neither acidic nor basic. Although plants tolerate a small range of soil pH quite well, extremely acidic or alkaline soils need to be adjusted for good plant health. Apr 19, 2019 The term âalkalineâ refers to waterâs pH level. Itâs measured in a range from 0 to 14. The only difference between this type of water and regular tap water is the pH level.
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(Redirected from Biuret reagent)
The characteristic color of a positive biuret test
The biuret test, also known as Piotrowski's test, is a chemical test used for detecting the presence of peptide bonds. In the presence of peptides, a copper(II) ion forms mauve-colored coordination complexes in an alkaline solution.[1] Several variants on the test have been developed, such as the BCA test and the Modified Lowry test.[2]
The biuret reaction can be used to assess the concentration of proteins because peptide bonds occur with the same frequency per amino acid in the peptide. The intensity of the color, and hence the absorption at 540 nm, is directly proportional to the protein concentration, according to the BeerâLambert law.
How to fix overflow coolant on dmg machine tool. A better test would be to check for combustion gasses in the cooling system. You need a test kit like this: Thanks for the link, I did not know this existed, should have done this before I took the oil cooler apart. Normally if it's an injector cup you will get fuel in the coolant.Pressure testing the cooling system would be helpful.
Despite its name, the reagent does not in fact contain biuret ((H2N-CO-)2NH). The test is named so because it also gives a positive reaction to the peptide-like bonds in the biuret molecule.
In this assay, the copper(II) binds with nitrogens present in the peptides of proteins. In a secondary reaction, the copper(II) is reduced to copper(I). Buffers, such as Tris and ammonia interfere with this assay, therefore rendering this assay inappropriate for protein samples purified from ammonium sulfate precipitation. Due to its insensitivity and little interference by free amino acids, this assay is most useful for whole tissue samples and other sources with high protein concentration.[3]
Procedure[edit]
An aqueous sample is treated with an equal volume of 1% strong base (sodium or potassium hydroxide) followed by a few drops of aqueous copper(II) sulfate. If the solution turns purple, it contains protein. 5â160 mg/mL can be determined. Peptides with the correct length of at least 3 amino acids are necessary for a significant, measurable colour shift with these reagents.[4]
Biuret reagent[edit]
The Biuret reagent is made of sodium hydroxide (NaOH) and hydrated copper(II) sulfate, together with potassium sodium tartrate,[5] the latter of which is added to chelate and thus stabilize the cupric ions. The reaction of the cupric ions with the nitrogen atoms involved in peptide bonds leads to the displacement of the peptide hydrogen atoms under the alkaline conditions. A tri- or tetra-dentate chelation with the peptide nitrogen produces the characteristic color.This is found with dipeptides (Datta, S.P., Leberman, R., and Rabin, B.R., Trans.Farad.Soc. (1959), 55, 2141).
The reagent is commonly used in the biuret proteinassay, a colorimetric test used to determine protein concentration by UV/VIS spectroscopy at wavelength 540 nm.
![]() High sensitivity variants of the biuret test[edit]
Two major modifications of the biuret test are commonly applied in modern colorimetric analysis of peptides: the bicinchoninic acid (BCA) assay and the Lowry assay. In these tests, the Cu+ formed during the biuret reaction reacts further with other reagents, leading to a deeper color.
In the BCA test, Cu+ forms a deep purple complex with bicinchoninic acid (BCA),[6] which absorbs around 562 nm, producing the signature mauve color. The water-soluble BCA/copper complex absorbs much more strongly than the peptide/copper complex, increasing the sensitivity of the biuret test by a factor of around 100: the BCA assay allows to detect proteins in the range of 0.0005 to 2 mg/mL). Additionally, the BCA protein assay gives the important benefit of compatibility with substances such as up to 5% surfactants in protein samples.
In the Lowry protein assay Cu+ is oxidized back to Cu2+ by MoVI in the FolinâCiocalteu reagent, which forms molybdenum blue (MoIV). Tyrosine residues in the protein also form molybdenum blue under these circumstances. In this way, proteins can be detected in concentrations between 0.005 and 2 mg/mL.[7] Molybdenum blue in turn can bind certain organic dyes such as malachite green and Auramine O, resulting in further amplification of the signal.[8]
In Poland, the biuret test is more commonly known as the Piotrowski test, in honor of the Polish toxological chemist, Jerzy Kazimierz Piotrowski (b. 1926) of Lodz.[9]
References[edit]
External links and notes[edit]
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Biuret_test&oldid=941934942#Biuret_reagent'
Water is alkaline when it has its pH level adjusted so that it is around 8 or 9, making it a base. Many of its proponents believe this improves your body's health because the body tends to gravitate towards being acidic, which can weaken your immune system, making you more susceptible to illness. There are expensive water ionizers that will release chemicals and supplements into the water to turn it alkaline. These are fine options, but you can also create your own alkaline water.
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Step 1
Fill a glass with about 8 ounces of water. Don't use straight tap water, since this usually has chemicals added during the purification process. Use distilled or filtered water, or water purified through reverse osmosis.
Step 2
Add 0.4 grams of sea calcium to the mixture. While this might seem like an insignificant amount, pH levels are sensitive, and this amount will make a big difference.
Step 3
Place half a capsule of magnesium complex into the water. Mix the water with a spoon or stirring stick. This method combats potential calcium or magnesium deficiencies in addition to making alkaline water, according to alkalinehealth.net.
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Consider purchasing a water ionizer and a water distiller to speed the process of making alkaline water. This is a good option for those who will drink multiple glasses a day.
Step 5
Use pH drops, which use highly-concentrated alkaline minerals to 'dramatically increase the alkalinity of the liquid, according to energiseforlife.com. This method is advantageous because pH drops can be packed in a purse or bag and added to any water drank throughout the day.
Step 6
Add lemon or lime juice to your water. This is the cheapest option, according to energiseforlife.com. Even though lemons and limes are acidic fruits, they have minerals in them that have an alkaline effect on your body, although they are better used as a quick fix than a permanent solution since this option's health benefits don't stand up to other alternatives in the long run.
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