Cell densities in the cyanobacteria cultures were estimated with previously determined linear regression models between the optical density (OD) and the number of cells (N mL−1) following a procedure according to Śliwińska-Wilczewska et al. [54 (link)] for Aphanizomenon sp. and Nostoc sp. and Barreiro Felpeto et al. [89 (link)] for N. spumigena. N was counted using a Bürker chamber [90 ]. OD was measured spectrophotometrically at 750 nm with a Multiskan GO UV-VIS spectrophotometer (Thermo Scientific, Waltham, MA, USA). Cyanobacterial cell densities were examined for control and experiments with aqueous extract and cell-free filtrate from U. intestinalis additions after 7 and 14 days of the experiment.
Multiskan go uv vis spectrophotometer
Manufactured by Thermo Fisher Scientific
Sourced in United States
The Multiskan GO UV/Vis spectrophotometer is a laboratory instrument designed to measure the absorbance of light by samples in the ultraviolet and visible light spectrum. It is capable of performing quantitative and qualitative analyses of various biological and chemical samples.
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Lab products found in correlation
Azocasein, by Merck Group (1 mentions)
Colorflex ez spectrophotometer, by HunterLab (1 mentions)
Folin s reagent, by Merck Group (1 mentions)
Gallic acid, by Merck Group (1 mentions)
7800 uv vis spectrophotometer, by Jasco (1 mentions)
Tnbs reagent, by Merck Group (1 mentions)
Glycine, by Merck Group (1 mentions)
Accumet ab150, by Thermo Fisher Scientific (1 mentions)
Avance 2 spectrometer, by Bruker (1 mentions)
13 protocols using multiskan go uv vis spectrophotometer
1
Estimating Cyanobacteria Cell Densities
2
Quantifying Bacterial Proteolytic Activity
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Proteolytic activity of bacterial strains was quantified using Azocasein (Sigma-Aldrich) as substrate. One hundred μL of a 3% (w/v) Azocasein stock solution were added to 100 μL of cell free supernatant fluid and 300 μL of 50 mM Na2HPO4 pH 7.5. The negative control was set up with 100 μL of not inoculated milk. The mixture was incubated at 37°C for 1 h and the reaction was stopped by adding 500 μL of 20% (w/v) trichloroacetic acid (TCA). The sample was centrifuged at 12,000 g for 10 min and absorbance of the supernatant was measured at 366 nm using Multiskan GO UV/Vis spectrophotometer (Thermo Fisher Scientific). Absorbance of the blank (500 μL not incubated sample plus 500 μL of TCA 20%), and of the negative control were subtracted from sample absorbance. The results are reported as OD366.
3
Determining Oil Color, β-Carotene, and Fatty Acid Properties
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The oil color (L, a* and b*) was determined by a ColorFlex EZ spectrophotometer (HunterLab, Reston, VA, USA), as described by Izuddin et al. [2 (link)]. The β-carotene was extracted from oil samples using acetone, as described by Biswas et al. [20 (link)], and the absorbance of β-carotene was measured at 449 nm using Multiskan™ Go UV/VIS spectrophotometer (Thermo Scientific, Waltham, MA, USA). Free fatty acid (FFA) and acid value (AV) were determined according to Japir et al. [21 (link)]. A total of 5 g of oil sample was mixed with 50 mL of pre-neutralized isopropanol (Merck, Darmstadt, Germany) in a 100 mL conical flask. The mixture was added to 500 µL of 1% (w/v) phenolphthalein indicator and heated to 40 °C. The mixture was titrated with 0.1 N sodium hydroxide (Merck, Darmstadt, Germany) until a pink color formed for at least 30 s. The FFA and AV were calculated according to the following formula:
where 25.6 is the formula for FFA determination and the equivalent factor for palmitic acid is as follows:
where 2.19 is the conversion factor for palmitic acid.
where 25.6 is the formula for FFA determination and the equivalent factor for palmitic acid is as follows:
where 2.19 is the conversion factor for palmitic acid.
4
Laccase Enzyme Activity Quantification
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Laccase activity was determined by following the oxidation of ABTS as the substrate for laccase according to Bourbonnais et al. (1998 (link)). The enzyme activity was assayed at 30 °C using 0.5 mM ABTS in 20 mM acetate buffer pH 3 and a suitable amount of enzyme. ABTS oxidation was followed by monitoring the changes in absorbance at 420 nm (ε = 3600 M−1 cm−1) against a blank with 20 mM acetate buffer pH 3 during 2 min of incubation. All assays were performed in triplicate in flat bottom 96 well microplates and the absorbance was measured using a Multiskan™ GO UV/Vis spectrophotometer (Thermo Scientific). One unit was defined as the amount of laccase that oxidized 1 μmol of ABTS substrate per minute.
5
Mangosteen Peel Extract Total Phenolic Content
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The
total phenolic content (TPC) of mangosteen extract was determined
according to the Folin–Ciocalteu colorimetric method, adapted
for a 96-well microplate procedure.17 (link) Briefly,
50 μL of mangosteen peel extract (100 μg mL–1) was mixed with 50 μL of Folin’s reagent
(Sigma-Aldrich); after 5 min, 200 μL of a sodium carbonate solution
(20%, w/w) was added to the wells to alkalize the medium and form
the blue phenolate anions. The absorbance was measured at 725 nm after
15 min in the dark, using a Thermo Scientific Multiskan GO UV–Vis
spectrophotometer. A hydroethanolic solution (60%, v/v) was used as
a blank, and gallic acid (Sigma-Aldrich) was used as standard (y = 0.019x – 0.065, R2 = 0.9997).
The analysis was carried out in triplicate, and the result of mangosteen
peel extract TPC was expressed in mg gallic acid equivalent (mg GAE)
g–1 extract.
total phenolic content (TPC) of mangosteen extract was determined
according to the Folin–Ciocalteu colorimetric method, adapted
for a 96-well microplate procedure.17 (link) Briefly,
50 μL of mangosteen peel extract (100 μg mL–1) was mixed with 50 μL of Folin’s reagent
(Sigma-Aldrich); after 5 min, 200 μL of a sodium carbonate solution
(20%, w/w) was added to the wells to alkalize the medium and form
the blue phenolate anions. The absorbance was measured at 725 nm after
15 min in the dark, using a Thermo Scientific Multiskan GO UV–Vis
spectrophotometer. A hydroethanolic solution (60%, v/v) was used as
a blank, and gallic acid (Sigma-Aldrich) was used as standard (y = 0.019x – 0.065, R2 = 0.9997).
The analysis was carried out in triplicate, and the result of mangosteen
peel extract TPC was expressed in mg gallic acid equivalent (mg GAE)
g–1 extract.
6
Quantifying Milk Protein Hydrolysis
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The experimental set-up made it possible to calculate the net proteolytic activity produced during 2 weeks of storage at 37°C after a heat treatment simulating UHT process and storage (as described in Marchand et al., 2008 , 2009a ). Hydrolysis of proteins was measured by the determination of the release of a-amino groups by the trinitrobenzenesulfonic acid (TNBS) method. The free amino groups react with the TNBS reagent (Sigma-Aldrich) at pH 9.2 in the dark. A yellow-orange colour develops and its intensity is determined by absorption measurements at 420 nm. The degree of proteolysis is calculated from the increase in absorption after 2 weeks of storage at 37°C and expressed as mmol of glycine equivalents mL-1 milk, using glycine (2.5, 2.25, 2, 1.75, 1.5, 1.25, 1, 0.75, 0.5, 0.25 e 0 mM; Sigma-Aldrich) to create a standard curve. The experiment was repeated twice, first in macro method (experiment A using a 7800 UV/VIS spectrophotometer; JASCO, Easton, MD, USA) and second time in micro method (experiment B using a Multiskan GO UV/Vis spectrophotometer (Thermo Fisher Scientific).
7
Mouthwash Stability Study: Organoleptic and Anti-Biofilm Analysis
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Samples were stored at 25 or 40 °C for six months with eight sampling points (0, 3, 7, 14, 21, 30, 90, and 180 days) in 7 mL sample vials made of neutral glass (Type IB) and closed with polypropylene screw caps (Fisher Scientific, Loughborough, UK). Organoleptic properties such as color, odor, and appearance were monitored. Color intensity was measured by UV spectroscopy (Multiskan Go UV–VIS spectrophotometer, Thermo Fisher Scientific, Paisley, UK) at wavelengths ranging from 300 to 700 nm. Odor was subjectively assessed by the investigator. The pH was measured with a digital pH meter (Accumet AB150, Fisher Scientific, Loughborough, UK). For each sample, three independent measurements were performed, and data were reported as the mean of the replicates. pH values from the stability data were analyzed using a two-way analysis of variance (ANOVA) with Tukey’s and Sidak post-test with an a priori level significance of 0.05 to detect statistically significant differences between the time and temperature from the mouthwash formulations and control. Sedimentation was visually assessed after centrifuging 1 mL of each sample at 5000 rpm for 5 min [44 (link)] at room temperature using a Jouan B4i Centrifuge (Hemel Hampstead, UK). In vitro anti-biofilm activity was tested as described above, at all time-points of the stability study.
8
Determination of Total Phenolic Content
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The TPC was determined by the Folin–Ciocalteau method, as described previously [20 (link)]. In brief, the phenolic extracts (60 µL) were mixed with 750 µL of 10% Folin–Ciocalteau reagents (v/v) for 5 min. Then, 600 µL of 7.5% Na2CO3 (w/v) solution was added, and the mixture was incubated at 25 °C in the dark for 2 h. The absorbance of the mixture was measured at 765 nm by a Multiskan GO UV-Vis spectrophotometer (Thermo Scientific, Vantaa, Finland). Gallic acid was used as the standard (0 to 0.400 mg/mL), and the results were expressed as mg gallic acid equivalents (GAE)/g sorghum sample dry basis (db).
9
Quantifying Extractable Color in Red Pepper
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The extractable color was measured according to ASTA 20.0 method. An amount of 1 g of dried red pepper powder was transferred in acetone added 100 mL volumetric flask and shaken in the dark condition for 16 h. The absorbance of the extract was measured at 460 nm using a Thermo Scientific Multiskan GO UV/VIS spectrophotometer.
I f is a correction factor that is calculated by the absorbance of a standard solution of potassium dichromate, ammonium sulfate and cobalt sulfate (ASTA [18] ).
I f is a correction factor that is calculated by the absorbance of a standard solution of potassium dichromate, ammonium sulfate and cobalt sulfate (ASTA [18] ).
10
Analyzing Protein Aggregation by UV-Vis Spectroscopy
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UV-Vis spectroscopy of the samples was performed by using a Multiskan GO UV/Vis spectrophotometer (Thermo Fisher Scientific, Waltham, MA, USA). 200 µL of samples were loaded onto a 96 wellplate. The spectra were recorded from 280 to 360 nm and were corrected for the suitable buffers. The optical density (OD) at 350 nm was used as in indication of turbidity. The aggregation index (AI) was calculated using the OD of the sample at 280 nm and 350 nm (equation ( 1)). AI is a parameter that is a measure of aggregate content, though it does not provide any details of particle size distribution. The stressed samples were centrifuged at 8000 rpm for 10 min, followed by careful separation of pellet and the supernatant. The amount of protein in the supernatant was analyzed as protein loss (%), which was calculated using equation (2) , where 'Initial A 280 ′ is the absorbance of sample at 280 nm before subjecting it to stress and 'Final A 280 ′ is the absorbance of supernatant at 280 nm after the sample has been subjected to stress.
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