Densitometric studies

Handelman, GJ, Snodderly, DM, Krinsky, NI, Russett, MD, and Adler, AJ, 1991a. Biological control of primate macular pigment—Biochemical and densitometric studies. Invest Ophthalmol Vis Sci 32, 257-267. 

Chavassieux P, Garnero P, Duboeuf F, Vergnaud P, Brunner-Ferber F, Del-mas PD, et al (2001) Effects of a new selective estrogen receptor modulator (MDL 103,323) on cancellous and cortical bone in ovariectomized ewes a biochemical, histomorphometric, and densitometric study. J Bone Miner Res 16 89-96... 

In Fig. 9.5 is shown the first, and to our knowledge, only direct experimental plot of the volume of both the folded and unfolded states of a protein. The densitometric studies yielded directly the volume V of Snase as a function of temperature for the folded state (below the transition temperature, crosses) and for the unfolded state (above the transition temperature, diamonds). It can be seen as well from Fig. 9.5 that the increase in V of the native state of Snase with temperature is not linear indeed the folded state a decreases significantly as the temperature increases while at high temperature... 

High-perfomance thin-layer plates (HPTLC) are very useful for lipid analysis (82). Such plates are made of fine particles of narrow size distribution and have excellent resolving power. The amount of sample can be reduced considerably from that applied to conventional TLC plates, and numerous samples can be used with minimal amounts of the mobile phase. HPTLC plates are also used frequently in densitometric studies on lipids. Commercially prepared reversed-phase TLC plates are... 

GJ Handehnan, DM Snodderly, N1 Krinsky, MD Russett, AJ Adler. Biological control of primate macular pigment. Biochemical and densitometric studies. Invest... 

Escribano A, Revilla M, Hernandez ER, et al. 1997. Effect of lead on bone development and bone mass a morphometric, densitometric, and histomorphometric study in growing rats. Calcif Tissue Int 60(2) 200-203. 

Dwivedi et al. used a thin-layer chromatographic densitometric and ultraviolet spectrophotometric methods for the simultaneous determination of primaquine and a new antimalarial agent, CDRI compound number 80/53 [68]. The new antimalari-al agent, compound 80/53 is unstable in acidic conditions where it is converted into primaquine. To conduct stability studies of this compound, thin-layer chromatography densitometric and ultraviolet spectrophotometric determination methods were developed. These methods are also suitable of the determination of compound 80/53 or primaquine in bulk and pharmaceutical dosage forms. 

Starting with the first IPCR study, gel electrophoresis retains its potential as a fast and easy method for end-point determination of DNA amplificate for IPCR assays [10, 24, 25, 29, 31, 35, 36, 38, 39, 64], Readout is performed by intercalation fluorescence markers (e.g., ethidium bromide) and photometric/densitometric quantification of band signal intensities. The direct addition of a double-strand specific intercalation marker to the PCR amplificate and subsequent measurement of fluorescence in microwells proved to be of insufficient sensitivity for the quantification of IPCR amplificate [37]. Alternative approaches, such as radioactive labeling during PCR and subsequent imaging [33], were carried out but are not well suited for routine clinical application because of additional methodological requirements. An advantage of gel electrophoresis is the possibility of simultaneous amplificate detection for multiplex IPCR [41] and the ability to detect nonspecific amplification products. 

Shellard and Alam(31 ) in 1968 have made a detailed study of the densitometric method for TLC. 

Commercial precoated layers on glass support are used in virtually all analyses. HPTLC uses plates that are smaller (10 x 10 or 10 x 20 cm), have a thinner (0.1-0.2 mm) layer composed of sorbent with a finer mean particle size (5-6 pm) and are developed over shorter distances (ca. 3-7 cm), as compared to classical 20 X 20 cm TLC plates which are generally 20 X 20 cm with a 0.25-mm layer and developed for 10-12 cm. HP plates provide improved resolution, shorter analysis time, higher detection sensitivity, and improved in situ quantification and are used for industrial pharmaceutical densitometric quantitative analyses. TLC plates are usually used for qualitative identification and purity studies as contained in pharmacopeias. 

Fig. 4. SDS-PAGE gel of CFi preincubated in SDS buffer at 20 C for 20 min (ieft panel, first column) and the CFq Fi complex preincubated in SDS buffer at 20 C for 20 min or at 95 C for 5 min (left panel, second and third columns, respectively). Right panel, densitometric scan of SDS-PAGE gel containing molecular-weight standards. The second and third densitometric scans are for the corresponding gel strips in the left panel. Gel-strip images are from Graber, Fromme, Schmidt and Boekema (1988) Structure of the ATP-synthase from chioropiasts as revealed from biochemical studies and election microscopy, in The Ion Pumps Structure, Function and Reguiation, p 68. Alan R Liss. Densitometric-scan images are from Fromme, Boekema and Graber (1987) Isolation and characterization of a supramolecular complex of subunit III of the ATP synthase from chioropiasts. Z Naturforsch 42C 1241.

TLC is useful both as an analytical and a preparative technique, and substances tentatively identified by TLC may be further characterized by various analytical techniques such as nuclear magnetic resonance spectrometry, mass spectrometry, or gas liquid chromatography. Moreover, many specific chemical detection tests are available to help identify substances separated by TLC. TLC is a microanalytical procedure and provides for separations and at least tentative identification of substances in the milligram (mg), microgram (/ig), and nanogram (ng) range. TLC can provide the biochemist with a method of eluting separated substances from plates for quantitative analyses. Recent studies indicate that elution techniques may not be the best alternative for quantitative analyses of many substances separated by TLC and that the preferred method may involve quantitative in situ densitometric analysis [1,2]. 

---