KOSEN 한인과학기술자네트워크

>DNS method 를 통해서 D-galactose 정량을 하고 있습니다. > >농도가 0.1mg/ml 이하에서는 값이 0으로 나오는데 > >DNS method 를 사용해서 정량할수 있는 최소값이 얼마인지 궁금합니다. > >그리고 관련논문도 필요합니다. > >좋은하루 보내세요... ============================================= Galactose의 정량에 관한 논문을 찾기가 쉽지 않네요. Effect of galactose feeding on the improved production of hirudin in fed-batch cultures of recombinant Saccharomyces cerevisiae Issue: Volume 19, Number 5 Date: November 1998 Pages: 385 - 388 를 찾아보시면 관련 참고 문헌이 나올 겁니다. 일단은 glucose assay와 관련된 방법을 올려 드립니다. 두 원리는 같기 때문에 sensitivity에 관해서도 크게 차이가 없을 것 같습니다. 단, somogyi-nelson method와 비슷하지만 sensitivity가 0.05~5mg glucose/ml로 somogyi-nelson method의 ~10~100ug/ml 보다 낮습니다. Method This method tests for the presence of free carbonyl group (C=O), the so-called reducing sugars. This involves the oxidation of the aldehyde functional group present in, for example, glucose and the ketone functional group in fructose. Simultaneously, 3,5-dinitrosalicylic acid (DNS) is reduced to 3-amino,5-nitrosalicylic acid under alkaline conditions: oxidation aldehyde group ----------> carboxyl group reduction 3,5-dinitrosalicylic acid ----------> 3-amino,5-nitrosalicylic acid Because dissolved oxygen can interfere with glucose oxidation, sulfite, which itself is not necessary for the color reaction, is added in the reagent to absorb the dissolved oxygen. The above reaction scheme shows that one mole of sugar will react with one mole of 3,5-dinitrosalicylic acid. However, it is suspected that there are many side reactions, and the actual reaction stoichiometry is more complicated than that previously described. The type of side reaction depends on the exact nature of the reducing sugars. Different reducing sugars generally yield different color intensities; thus, it is necessary to calibrate for each sugar. In addition to the oxidation of the carbonyl groups in the sugar, other side reactions such as the decomposition of sugar also competes for the availability of 3,5-dinitrosalicylic acid. As a consequence, carboxymethyl cellulose can affect the calibration curve by enhancing the intensity of the developed color. Although this is a convenient and relatively inexpensive method, due to the relatively low specificity, one must run blanks diligently if the colorimetric results are to be interpreted correctly and accurately. One can determine the background absorption on the original cellulose substrate solution by adding cellulase, immediately stopping the reaction, and measuring the absorbance, i.e. following exactly the same procedures for the actual samples. When the effects of extraneous compounds are not known, one can effectively include a so-called internal standard by first fully developing the color for the unknown sample; then, a known amount of sugar is added to this sample. The increase in the absorbance upon the second color development is equivalent to the incremental amount of sugar added. -------------------------------------------------------------------------------- List of Reagents and Instruments A. Equipment Test tubes Pipets Spectrophotometer B. Reagents Dinitrosalicylic Acid Reagent Solution, 1% Dinitrosalicylic acid: 10 g Phenol: 2 g (optional, see Note 1) Sodium sulfite: 0.5 g Sodium hydroxide: 10 g Add water to: 1 liter Potassium sodium tartrate solution, 40% -------------------------------------------------------------------------------- Procedures Add 3 ml of DNS reagent to 3 ml of glucose sample in a lightly capped test tube. (To avoid the loss of liquid due to evaporation, cover the test tube with a piece of paraffin film if a plain test tube is used.) Heat the mixture at 90º C for 5-15 minutes to develop the red-brown color. Add 1 ml of a 40% potassium sodium tartrate (Rochelle salt) solution to stabilize the color. After cooling to room temperature in a cold water bath, record the absorbance with a spectrophotometer at 575 nm. 3ml 1ml O.D. reagent --->----+ Rochelle soln --->----++-------> at 575nm | | | | || | +-+--+ +-++-+ | | heat | | | | --------> | | | | | | | | | | |____| |____| 3ml sample soln -------------------------------------------------------------------------------- Notes Phenol, up to 2g/l, intensifies the color density. It changes the slope of the calibration curve of absorbance versus glucose concentration but does not affect the linearity. The above procedure yields an absorbance of 1 for 1 g/l of glucose in the original sample in the absence of phenol in the reagent, as opposed to an absorbance of 2.5 for 1 g/l of glucose in 2 g/l of phenol. This property can be exploited to achieve the maximum sensitivity for dilute samples. -------------------------------------------------------------------------------- Questions How much time was needed for the complete color development? Justify your answer with a plot of color intensity as a function of time. Obtain an absorption spectrum over wavelengths in the visible range (i,e. 400-700 nm). Justify the use of 575 nm chosen in the Procedure. Find the procedures for at least two other methods commonly employed to measure sugar concentrations. List the advantages and disadvantages of these methods. -------------------------------------------------------------------------------- References Miller, G.L., Use of dinitrosalicylic acid reagent for determination of reducing sugar, Anal. Chem., 31, 426, 1959.

Standard curve 를 그릴 때 0.1 mg/ml ~ 1 mg/ml 사이에서 그렸던 것 같습니다. >DNS method 를 통해서 D-galactose 정량을 하고 있습니다. > >농도가 0.1mg/ml 이하에서는 값이 0으로 나오는데 > >DNS method 를 사용해서 정량할수 있는 최소값이 얼마인지 궁금합니다. > >그리고 관련논문도 필요합니다. > >좋은하루 보내세요...

>>DNS method 를 통해서 D-galactose 정량을 하고 있습니다. >> >>농도가 0.1mg/ml 이하에서는 값이 0으로 나오는데 >> >>DNS method 를 사용해서 정량할수 있는 최소값이 얼마인지 궁금합니다. >> >>그리고 관련논문도 필요합니다. >> >>좋은하루 보내세요... >============================================= >Galactose의 정량에 관한 논문을 찾기가 쉽지 않네요. > >Effect of galactose feeding on the improved production of hirudin in fed-batch cultures of recombinant Saccharomyces cerevisiae >Issue: Volume 19, Number 5 >Date: November 1998 >Pages: 385 - 388 >를 찾아보시면 관련 참고 문헌이 나올 겁니다. > >일단은 glucose assay와 관련된 방법을 올려 드립니다. >두 원리는 같기 때문에 sensitivity에 관해서도 크게 차이가 없을 것 같습니다. > >단, somogyi-nelson method와 비슷하지만 >sensitivity가 0.05~5mg glucose/ml로 somogyi-nelson method의 >~10~100ug/ml 보다 낮습니다. > > >Method >This method tests for the presence of free carbonyl group (C=O), the so-called reducing sugars. This involves the oxidation of the aldehyde functional group present in, for example, glucose and the ketone functional group in fructose. Simultaneously, 3,5-dinitrosalicylic acid (DNS) is reduced to 3-amino,5-nitrosalicylic acid under alkaline conditions: > oxidation >aldehyde group ----------> carboxyl group > > reduction >3,5-dinitrosalicylic acid ----------> 3-amino,5-nitrosalicylic acid > >Because dissolved oxygen can interfere with glucose oxidation, sulfite, which i>tself is not necessary for the color reaction, is added in the reagent to absorb the dissolved oxygen. >The above reaction scheme shows that one mole of sugar will react with one mole of 3,5-dinitrosalicylic acid. However, it is suspected that there are many side reactions, and the actual reaction stoichiometry is more complicated than that previously described. The type of side reaction depends on the exact nature of the reducing sugars. Different reducing sugars generally yield different color intensities; thus, it is necessary to calibrate for each sugar. In addition to the oxidation of the carbonyl groups in the sugar, other side reactions such as the decomposition of sugar also competes for the availability of 3,5-dinitrosalicylic acid. As a consequence, carboxymethyl cellulose can affect the calibration curve by enhancing the intensity of the developed color. > >Although this is a convenient and relatively inexpensive method, due to the relatively low specificity, one must run blanks diligently if the colorimetric results are to be interpreted correctly and accurately. One can determine the background absorption on the original cellulose substrate solution by adding cellulase, immediately stopping the reaction, and measuring the absorbance, i.e. following exactly the same procedures for the actual samples. When the effects of extraneous compounds are not known, one can effectively include a so-called internal standard by first fully developing the color for the unknow>n sample; then, a known amount of sugar is added to this sample. The increase in the absorbance upon the second color development is equivalent to the incremental amount of sugar added. > > > >-------------------------------------------------------------------------------- > >List of Reagents and Instruments >A. Equipment >Test tubes >Pipets >Spectrophotometer >B. Reagents >Dinitrosalicylic Acid Reagent Solution, 1% >Dinitrosalicylic acid: 10 g >Phenol: 2 g (optional, see Note 1) >Sodium sulfite: 0.5 g >Sodium hydroxide: 10 g >Add water to: 1 liter >Potassium sodium tartrate solution, 40% > > >-------------------------------------------------------------------------------- > >Procedures >Add 3 ml of DNS reagent to 3 ml of glucose sample in a lightly capped test tube. (To avoid the loss of liquid due to evaporation, cover the test tube with a piece of paraffin film if a plain test tube is used.) >Heat the mixture at 90º C for 5-15 minutes to develop the red-brown color. >Add 1 ml of a 40% potassium sodium tartrate (Rochelle salt) solution to stabilize the color. >After cooling to room temperature in a cold water bath, record the absorbance with a spectrophotometer at 575 nm. > 3ml 1ml O.D. > reagent --->----+ Rochelle soln --->----++-------> at 575nm > | | | | || | > +-+--+ +-++-+ > | | > heat | | > | | --------> | | > | | | | > | | | | > |____| |____| > 3ml sample soln > > > >-------------------------------------------------------------------------------- > >Notes >Phenol, up to 2g/l, intensifies the color density. It changes the slope of the calibration curve of absorbance versus glucose concentration but does not affect the linearity. The above procedure yields an absorbance of 1 for 1 g/l of glucose in the original sample in the absence of phenol in the reagent, as opposed to an absorbance of 2.5 for 1 g/l of glucose in 2 g/l of phenol. This property can be exploited to achieve the maximum sensitivity for dilute samples. > > >-------------------------------------------------------------------------------- > >Questions >How much time was needed for the complete color development? Justify your answer with a plot of color intensity as a function of time. >Obtain an absorption spectrum over wavelengths in the visible range (i,e. 400-700 nm). Justify the use of 575 nm chosen in the Procedure. >Find the procedures for at least two other methods commonly employed to measure sugar concentrations. List the advantages and disadvantages of these methods. > > >-------------------------------------------------------------------------------- > >Refe>rences >Miller, G.L., Use of dinitrosalicylic acid reagent for determination of reducing sugar, Anal. Chem., 31, 426, 1959. >