Application Notes

DNA Concentration Measurement at 260 nm Using Photopette® Bio

The objective of this application note is to demonstrate how Photopette Bio can be used for direct DNA concentration measurement and DNA purity for unknown samples. Furthermore, it acts as a handy guide to get you started with Photopette, and outlines application-specific parameters for reference.

DNA (deoxyribonucleic acid) concentration measurement is a commonly performed procedure in life science and biomedical research laboratories. A spectrophotometer is able to determine DNA concentration as well as its purity [1]. It is based on the principles that nucleic acids absorb ultraviolet (UV) light at a specific wavelength. For pure DNA samples, the maximum absorbance occurs over a broad peak at around 260 nm; at 280 nm it only absorbs about half as much UV light compared to 260 nm [2]. DNA absorbs UV light due to heterocyclic rings of the nucleotides, its sugar-phosphate backbone does not contribute to this absorption [3]. Factors such as pH and ionic strength can further affect the absorbance spectrum.

Measuring pH using Photopette® Cell

Growth of the cyanobacteria Spirulina (Arthrospira) Platensis occurs at an optimum pH of 9 – 10 [1]. Due to the very high salinity of the culture medium, conventional pH meters do not provide accurate results. During the cultivation process, the production of primary and secondary metabolites in the culture give rise to a pH change in the medium and drive the process to a sub-optimal pH range. In order to achieve an optimal growth, the pH of the cultivation medium needs to be frequently monitored and adjusted to fall within the optimum pH range. An ideal pH indicator for monitoring the pH of the medium must have a response in the range of pH 9 – 11. Thymolphthalein has been chosen as the pH indicator for the current experiment because its response range lies between pH 9.3 to 10.5. The colour transition occurs from colourless (below pH 9.3) to blue (above 10.5). The molar extinction co-efficient for the blue thymolphthalein dianion is 38,000 M−1 cm−1 at 595 nm [2].

Direct Turbidity Measurement Using Photopette®

Determining Turbidity of an aqueous solution is a frequently used procedure to estimate the quality of water, or even concentration of suspended particles such as cells, bacteria, and mud.

Turbidity can be defined as a decreased in the transparency of a solution due to the presence of suspended and some dissolved substances, which causes incident light to be scattered, reflected and attenuated rather than transmitted in straight lines; the higher the intensity of the scattered or attenuated light, the higher the value of turbidity [1].

Nephelometric turbidity units (NTU) are often used to express turbidity. NTU can be defined as the intensity of light at a specified wavelength scattered or attenuated by suspended particles or absorbed at a method-specific angle (90 degrees), from the path of the incident light compared to a synthetic chemically prepared standard [1].

Following the USEPA method and ISO 7027 method, the turbidity is measured at wavelengths of 570 nm and 850 nm respectively. This application note highlights the measurements of OD at these two wavelengths using the Photopette®.

Determination of Lactate Concentration Using Photopette® Cell

This application note provides an easy and fast enzymatic assay to quantify lactate in biological samples such as serum, plasma, urine, cell culture/fermentation media or in food & beverage products using Photopette®.

During anaerobic glycolysis, energy is produced. In this process, lactate dehydrogenase (LDH) catalyses the oxidation of lactate to pyruvate and an equimolar amount of nicotinamide adenine dinucleotide (NAD+) is reduced to its reduced form NADH. The amount of NADH produced is directly proportional to the lactate concentration in the sample [1]. The produced NADH is measured by its absorbance at 340 nm.

Determination of Ethanol In Alcoholic Beverages Using Photopette® Cell

The objective of this application note is to demonstrate how Photopette® Cell can be used to quantify the amount of ethanol in beverages on the example of wine.

Hela Cell Counting by Optical Density Measurements with Photopette®

This application note is to demonstrate how Photopette® can be used for measurement of cell number by optical density. Advantageously, Photopette® enables cell number measurements directly in the cell culture hood. This application note demonstrated cell number measurements of HeLa cell lines, how to prepare a calibration curve and to determine the biomass in the cell suspension. Furthermore, it acts as a handy guide to get you started with Photopette®, and outlines application-specific parameters for reference.

Measuring Cell-Viability by Resazurin (Alamarblue) Assay using Photopette® Cell

This application note is to demonstrate how Photopette Cell can be used to measure cell-viability of eukaryotic cells using a Resazurin Assay. Furthermore, it acts as a handy guide to get you started with Photopette Cell, and outlines application-specific parameters for reference.

Protein Measurement using Bradford Assay and Photopette®

This application note is to demonstrate how Photopette® can be used for measurement of an unknown protein sample using a standard Bradford assay kit. Furthermore, it acts as a handy guide to get you started with Photopette® and outlines application-specific parameters for reference.

Measuring Protein Concentration Directly using Photopette® Bio

This application note is to demonstrate how the Photopette® Bio device can directly measure protein concentrations in an unknown sample. Furthermore, it acts as a handy guide to get you started with Photopette® Bio and outlines application-specific parameters for reference.

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