Agilent Manuals

Effect of pH on Protein Size Exclusion Chromatography Application Note Introduction Determination of protein structure is key to understanding the function of many proteins. Molecule size is an indicator of structure and provides information on the quaternary structure of the protein. Many proteins undergo profound conformational changes in different solution conditions, with the most extreme being denaturation. Similar structural modifications may occur as a function of ionic strength, pH, temperature and changes in various other solution conditions. Proteins comprise amino acids, some of which have polar side chains or contain acidic or basic groups. At the isoelectric point, the protein is uncharged and charge repulsions of similar functional groups will be at a minimum, allowing aggregation to take place. Many proteins precipitate under these conditions, and even for proteins that remain in solution at their isoelectric point this is the pH of minimum solubility. At physiological pH most proteins are above their isoelectric point and have a net negative charge. A pH lower than the isoelectric point causes protonation of acidic groups and a net positive charge on the protein. In each case, the like- charges formed repel each other, reducing the likelihood of protein aggregation. However, in areas of larger charge density the intramolecular repulsion can lead to destabilization of the protein tertiary structure and subsequent unfolding. In some cases, this unfolding may lea...

This document describes the use of tetracyclines and the USP method1 for the analysis of the compound

This application note describes a trial of the purity and stability of stored L-ascorbic acid powder samples from four different manufacturers, and assesses degradation compounds and/or precursors from the production process.

This application note introduces the analysis of polysiloxane using GPC/SEC with RI and ELS detection on Agilent PLgel 5 µm MIXED-E column. Polysiloxanes are important commercial polymers used in applications such as lubricating oils, defoaming agents, and sealants. Analyzing these materials by gel permeation chromatography (GPC) is an important part of process and quality control procedures. Although polysiloxane is soluble in tetrahydrofuran (THF), it has the same refractive index as this solvent. Therefore, refractive index (RI) detection cannot be used with THF.

This document introduces the method of using Agilent PLgel columns for GPC to analyze mono-, di-, and tristearoylglycerol.

This document introduces the quantitative GPC analysis application of poly(vinyl chloride) (PVC) and plasticizers. PVC is a thermoplastic widely encountered in everyday life. It is light, non-flammable, robust and durable. PVC is permeable, does not deteriorate, is easy to maintain and its physical and mechanical characteristics make it ideal for many different uses. Unplasticized PVC has a high melt viscosity leading to some difficulties in processing. The finished product is also too brittle for many applications. In order to overcome these problems, it is routine to incorporate additives to the PVC. In addition to acting as impact modifiers, a number of polymeric additives may be considered as processing aids. Such materials are primarily included to ensure more uniform flow and hence improve surface finish. The properties of the final material are dependent on the molecular weight distribution of the PVC and the type and level of the added plasticizers. The analysis of the compounded material is, therefore, of primary importance, and GPC is the ideal analytical tool for its characterization. With their linear resolving capability over a wide molecular weight range, PLgel MIXED columns provide resolution of both polymer and additives, particularly with the high efficiency 5 µm particle size columns.

This document discusses methods for improving the extraction and purification of pharmaceutical compounds, as well as the use of FlowTrap columns to address issues caused by TFA acid.

This application note describes a fast and sensitive method for the determination of bisphenol-A in epoxy resins using GPC with an evaporative light scattering detector (ELSD). The method uses a narrow bore column and high flow rate for rapid separation, and Agilent ELSD provides excellent sensitivity and signal-to-noise ratio.

An efficient plasticizer additive analysis method

This article describes an optimized analysis method for sizing agents used in paper production, using gel permeation chromatography combined with an evaporative light scattering detector for qualitative and quantitative analysis. This method allows for monitoring and controlling the level of sizing agents in paper sizing fluids.

This application note describes the 5’-Nuclease PCR Assays for Foodborne Pathogen Detection using the Agilent-Stratagene Mx3000P Q-PCR System. This method is rapid, highly sensitive and specific.

This article describes a method for flow cytometric analysis of human primary cells using the Agilent 2100 bioanalyzer and on-chip staining. The transfection efficiency of primary cells can be determined using green fluorescent protein (GFP) as a reporter molecule. The advantages of using the compact 2100 bioanalyzer for monitoring transfection efficiency in primary cells include low cell consumption, high reproducibility of results, fast on-chip staining procedure, and ease of use.

This study explored the interference of Sybr®Green I on the performance of Agilent 2100 bioanalyzer. The results showed that Sybr®Green I had little effect on the performance of the analyzer.

This application note describes the use of the Agilent 2100 bioanalyzer to quickly verify siRNA integrity and determine optimal transfection conditions for gene silencing experiments.

This application note describes how the Agilent Technologies 2100 Bioanalyzer can be used to analyze protein extracts from transgenic seedlines. Accuracy and precision in the determination of protein size and concentration was sufficiently good to allow for the characterization of experimental seedlines based solely on expressed protein profiles.