S. Mattssona and J. Börjessonb
aDepartment of Radiation Physics, Lund University, Malmö University Hospital, SE-205 02, Malmö, Sweden
bDepartment of Diagnostic Radiology, County Hospital, SE-310 85 Halmstad, Sweden
X-ray fluorescence (XRF) is the emission of characteristic secondary (or fluorescent) x-rays from a material that is excited by bombardment of high-energy x-rays or gamma rays. The process in which a photon is absorbed by an atom by transferring all of its energy to an electron is called the photoelectric effect.
Marleen de Veij,a Peter Vandenabeeleb and Luc Moensa
bGhent University, Department of Archaeology and Ancient History of Europe, Belgium
According to the World Health Organisation (WHO), a counterfeit drug is one that is deliberately and fraudulently mislabelled with respect to identity and/or source. Counterfeiting can apply to both branded and generic products; counterfeit products may include products with correct or wrong ingredients, without active ingredients, with insufficient active ingredient or fake packaging.
Elina Kalenius and Pirjo Vainiotalo
During the last few decades, solution and solid state techniques have been utilised to obtain information about the properties of supramolecular host–guest complexes. Mass spectrometric analysis of these fragile non-covalent complexes has been focused on the determination of the molecular mass of the interacting molecules and the analysis has concentrated on the characterisation of covalent compounds. Since the invention of the soft ionisation techniques [namely ESI (electospray ionisation) and MALDI (matrix-assisted laser desorption/ionisation)] and their development for mass spectrometry (MS) instruments, the area and way that MS analysis is used have greatly changed and expanded.
Over the last two decades therapeutic antibodies have become the fastest growing area in pharmaceutical biotechnology. The medical significance of these therapeutic entities is highlighted by the commercial availability of about 20 products on the market with more than 160 candidates evaluated in different clinical trials. One reason for the success of antibodies as therapeutic agents is related to the large advancement in their biotechnological production via fermentation. Nowadays titers of about 4 g L–1 in 11-day fed-batch mode using the CHO BI HEX process are achievable using CHO-cells (CHO: chinese hamster ovary).
The first products launched on the market were lyophilised dosage forms, requiring a reconstitution step before medical application. One reason for this was a lack of knowledge to stabilise antibodies in a liquid form, because a number of factors have a negative impact on protein stability in solution. Furthermore, in order to avoid protein loss during the process, e.g. due to the formation of aggregates, it is important in the early development phase to be able to screen rapidly and identify buffer conditions that may have a stabilising effect and avoid protein aggregation. Currently, formulations have been developed allowing storage of antibodies in a liquid form for two to three years at 2–8°C.
Compared to NCEs (new chemical entities) biologics are quite complex molecules and a number of methods are necessary to characterise their protein structure. Additionally in their early purification and pre-formulation development phase methods are required that utilise just very small amounts of proteins for the evaluation of solution conditions that allow the stabilisation of the protein. Fluorescence spectroscopy has the characteristics that may fulfil some relevant criteria for studying protein stability during the early development phase; these are: (i) being a very sensitive method, (ii) rapid, (iii) allowing the rapid screening of a number of solution conditions, (iv) requiring minimal chemometric data analysis, and (v) having the potential for automation. Although fluorescence spectroscopy does not usually provide detailed structural information, as, for example, X-ray or nuclear magnetic resonance, the method has some potential applications in pharmaceutical biotechnology, because of its acute sensitivity to changes in the structural and dynamic properties of proteins due to solvent variations. A number of fluorescence spectroscopic experiments are available and can be carried out at different levels ranging from straightforward measurements of steady-state emission intensity to more or less sophisticated time-resolved experiments. The combination of various fluorescence observables obtained under time-resolved conditions, in particular, has increased dramatically the interpretation of fluorescence results.6 However, for the relative evaluation of solution conditions with regard to protein stability, intrinsic fluorescence spectroscopy is quite useful, especially when combined with a well-defined thermal protocol, in order to characterise the thermal conformational stability of proteins in solution as a function of their solution properties.
The application presented in this article is therefore focused on steady-state intrinsic tryptophan protein fluorescence (ITF). Applications using extrinsic fluorescence labels are not considered. The results from steady-state intrinisic tryptophan protein fluorescence are compared to results obtained from other biophysical methods (infrared spectroscopy and high sensitive micro-calorimetry).
Serveis Científicotècnics, Universitat de Barcelona, Lluís Solé i Sabarís, 1, 08028 Barcelona, Spain
Applications of infrared spectroscopy to solve problems related to cultural heritage have been growing steadily during the last few years. People working in the field of conservation and restoration have become increasingly aware of the potential and value of using instrumental analyses; this demand involves spectroscopists and scientists developing new methodologies that can be applied to samples from museums and other related institutions.
- Dried blood spots for Pb determination using solid sampling-graphite furnace atomic absorption spectrometry
- ICP-mass spectrometry: Let the isotopes do the talking!
- The role of MALDI-enabled linear ion trap mass spectrometry as a sensitive tool in tissue imaging
- X-ray fluorescence applications to art and cultural heritage: study of a Japanese print
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Gujarathi Dipak B. saidSir,
This is an excellent appl... 8 months ago
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Matrix suppression is ... 1 year ago
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As you sad atmospheric... 1 year ago
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