Two dilutions of each of the dipeptides Gly-Met, Gly-Phe, and Gly-Leu (Sigma) were prepared in the Biolog proprietary concentration range used in the Biolog PM 6–8 plates, using the medium recommended by Biolog. 100 μL of each dilution was added to duplicate wells of 96-well microtiter plates, along with 100 μL of each of the cells, prepared according to the instructions of Biolog. The microtiter plates were incubated at 37°C for 24–48 h and the optical density (A750) was measured by spectrophotometer. Control wells contained media without dipeptides.
Leu gly
Manufactured by Merck Group
Sourced in United States
Leu-Gly is a lab equipment product manufactured by Merck Group. It is a dipeptide compound consisting of the amino acids leucine and glycine. Leu-Gly is used as a standard in analytical techniques to identify and quantify the presence of these amino acids in various samples.
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Lab products found in correlation
Uv 160a, by Shimadzu (2 mentions)
Bradykinin fragment 1 7, by Merck Group (1 mentions)
Superdex peptide 10 300 column, by GE Healthcare (1 mentions)
Ninhydrin, by Merck Group (1 mentions)
M17 broth, by Merck Group (1 mentions)
Phe ala, by Merck Group (1 mentions)
Ultrafiltration membrane, by Merck Group (1 mentions)
5 protocols using leu gly
1
Growth Kinetics of Dipeptide Substrates
2
Peptide Molecular Weight Characterization
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The MWD of the peptides after hydrolysis was characterized using GPC. Hydrolysate samples were dissolved in 5 mg/mL HPLC-eluent, and undissolved particles were removed by centrifugation (5 min at 13,000× g) if required, followed by filtration (0.45 μm cellulose acetate filter). Size exclusion chromatography was performed with a Superdex Peptide 10/300 column (GE Healthcare) at 30 °C, with a flow rate of 0.9 mL/minute using an injection of 20 μL of a 5 mg/mL HPLC-eluent (7.4 g trifluoro acetic acid and 1173 g acetonitrile in 3500 g H2O) solution. The column was calibrated with 10 peptide standards: cytochrome C (M = 12,327), aprotinin (M = 6500), adrenocorticotropic hormone from porcine pituitary gland (M = 4567), insulin A-chain oxidized ammonium salt from bovine pancreas (M = 2532), angiotensinogen 1–14 renin substrate porcine (M = 1759), bradykinin salt (M = 1060), bradykinin fragment 1–7 (M = 757), bradykinin fragment 1–5 (M = 573), Ala-Ala-Ala-Ala-Ala (M = 373), and Gly-Leu (M = 188), all of which were from Sigma Aldrich, St. Louis, MO, USA. The eluate was monitored at 200 nm.
3
Analysis of Dairy Starter Bacteria and Dipeptides
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Dairy starter in the form of multi-strain cultures containing the following bacteria: Lactococcus lactis ssp. cremoris, Leuconostoc mesenteroides ssp. cremoris, and Lactococcus lactis ssp. lactis biovar diacetylactis was analyzed in the study (CHN-19 Chr. Hansen company).
The following eight dipeptides were used in the study: Ala-Ala, Ala-Phe, Phe-Ala, Leu-Gly, Lys-Leu, Tyr-Leu, Tyr-Phe and Ala-Pro (Sigma-Aldrich, Poland) and the following microbiological media were applied: M17 broth (acc. to TERZAGHI, Merck, Poland), phosphate buffer pH 7.0 (Fluka, Poland), and finally, the reagents as follows: ninhydrin (Sigma-Aldrich, Poland), trichloroacetic acid-TCA (POCH, Poland) and ethanol (POCH, Poland).
The following eight dipeptides were used in the study: Ala-Ala, Ala-Phe, Phe-Ala, Leu-Gly, Lys-Leu, Tyr-Leu, Tyr-Phe and Ala-Pro (Sigma-Aldrich, Poland) and the following microbiological media were applied: M17 broth (acc. to TERZAGHI, Merck, Poland), phosphate buffer pH 7.0 (Fluka, Poland), and finally, the reagents as follows: ninhydrin (Sigma-Aldrich, Poland), trichloroacetic acid-TCA (POCH, Poland) and ethanol (POCH, Poland).
4
Peptide Content Quantification Protocol
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A slightly modified procedure, developed by Church et al. [20 (link),42 (link)], was used to measure the sample peptide content. A hydrolysate solution with a concentration of 30 mg/mL was passed through a 0.22-μm membrane before ultra-filtration at 5-kDa MW cut-off (MWCO). Fifty milliliter was mixed with 2.0 mL of o-phthaldialdehyde at room temperature and allowed to stand for 2 min. A Shimadzu UV-160A (Kyoto, Japan) was used to measure absorbance at 340 nm. The peptide content was quantified using Leu-Gly (Sigma, St. Louis, MO, USA) as a standard.
5
Peptide Content Quantification Protocol
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The peptide content of the samples was measured by an ortho-phthaldialdehyde reagent with dipeptide (Leu-Gly) (Sigma, St. Louis, MO, USA) as a standard according to a modification of the method of Church et al. [34 (link)]. Prior to the measurement, the sample solution (30 mg/mL) was filtered through a 0.22-μm membrane, and the filtrate was passed through an ultrafiltration membrane (Millipore, Bedford, MA, USA) with an MW cut-off (MWCO) of 5000 Da. Then, 50 μL of the resulting permeate was mixed with 2 mL of the ortho-phthaldialdehyde reagent and incubated at ambient temperature for 2 min. The absorbance of the reaction mixture was subsequently determined using a spectrophotometer (UV-160A, Shimadzu, Taipei, Taiwan), which measured it as 340 nm.
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