Karl H. Norris

Co-pigmentation of anthocyanins in plant tissues and its effect on color

Glycosides of the 6 common anthocyanidins all formed co-pigment complexes with flavonoids and other compounds at pHs ranging from 2 to 5. The formation of co-pigment complexes resulted in a bathochromic shift in the visible λmax of the anthocyanins and a large increase in extinction at pH 3 and higher. These complexes apparently formed with both the red flavylium salts and the purple anhydro bases. The increase in extinction at pHs 3 to 5 was attributed to the stabilizing effect co-pigmentation had on the anhydro bases. The degree of co-pigmentation was a function of the concentration of the anthocyanins and the molar ratio of co-pigments to anthocyanins. Co-pigmentation offers an explanation for the infinite color variations that occur in flowers in a pH range where anthocyanins alone are virtually colorless.

The spectrophotometry of dense light-scattering material.

Abstract The spectrophotometry of dense light-scattering samples by means of a single-beam recording spectrophotometer is described. The optical path length of light traversing a light-scattering sample may be many times the sample depth. By adding CaCO 3 to reduced cytochrome c solutions, the intensity of absorption bands was intensified 70-fold as the result of a 70-fold increase of path length. A similar intensification of over tenfold was shown to exist in apple tissue. The photoreversible pigment which controls so many developmental responses of plants is demonstrated spectrophotometrically in intact corn coleoptiles. The spectra of dry yeast as well as dense yeast suspensions are presented. In addition to the typical cytochrome complement, a cyanide-sensitive absorption band at 640 mμ is shown. The spectra of intact lima bean seeds, both dry and imbibed, show spectral changes associated with germination processes.

Spectrophotometry of Human Hemoglobin in the near Infrared Region from 1000 to 2500 nm

Absorbance and first and second derivative absorbance spectra and quarter-millimolar absorptivity coefficients for hemoglobin species including oxy-, deoxy-, carboxy- and methemoglobin in the visible and in the near infrared regions from 620 nm to 2500 nm are presented. At wavelengths longer than 1500 nm, the absorbance and second derivative absorbance spectra of hemoglobin species are similar for all of the species. Absorption bands are present centred at 1690, 1740, 2056, 2170, 2290 and 2350 nm.

Anthocyanin, flavonol copigments, and pH responsible for larkspur flower color

Abstract The anthocyanin and flavonol glycosides in Larkspur flowers (cv. Dark Blue Supreme) are delphinidin 3-di( p -hydroxybenzoyl)glucosylglucoside, kaempferol 3-robinobioside-7-rhamnoside (robinin), kaempferol 3-rutinoside, kaempferol 7-rhamnoside, and kaempferol 3-(caffeylgalactosylxyloside)-7-rhamnoside. As young flowers age the pH of epidermal tissue increases from 5·5 to 6·6 and the color of many of the cells changes from moderate reddish-purple to light purplish-blue. Many of the older cells also contain blue crystals. Visible absorption spectra of moderate reddish-purple and light purplish-blue cells were simulated with a solution of the anthocyanin (10 −2 M) plus robinin (5 × 10 −3 M) at pH 5·6 and 7·1, respectively. Changes in the absorption spectra of living tissue with heating or cooling and of concentrated solutions of the anthocyanin with dilution or moderate heat, indicate that in the natural state the pigment is present in an associated form.

Co-pigmentation effect of quercetin glycosides on absorption characteristics of cyanidin glycosides and color of Red Wing azalea

Abstract A quercetin 5-methyl ether and five quercetin glycosides were isolated from flowers of Red Wing azalea1 but were found only in trace amounts in an orange sport of this cultivar. The anthocyanins (cyanidin glycosides) extracted from the orange and red flowers were identical, even though the absorption spectra of the intact cells differed. The absorption spectrum of the orange sport was simulated with a 10−3 M aqueous solution of cyanidin 3,5-diglucoside at the pH of the tissue, 2·8. The absorption spectrum of Red Wing was matched with cyanidin 3,5-diglucoside at the same concentration and pH, co-pigmented with the 3-rhamnoside or galactoside of quercetin.

A stable blue non-metallic co-pigment complex of delphanin and C-glycosylflavones in Prof. Blaauw Iris

Abstract The pigment of Prof. Blaauw Iris is a stable blue non-metallic co-pigment complex of C -glycosylflavones and the anhydro-base of delphanin [delphinidin 3-( p -coumaroylrutinoside)-5-glucoside]. At a concentration comparable to that within the plant cell the reconstituted complex is stable and has an absorption spectrum matching that of the intact cell. The blue pigment is associated with a pectin and the co-pigment C -glycosylflavones are 6- C -β- d -glucopyranosylgenkwanin (swertisin), O -xylosylswertisin, 8- C -β- d -glucopyranosylapigenin (vitexin), 6- C -β- d -glucopyranosylluteolin (iso-orientin) and 6- C -β- d -glucopyranosyl-7- O -methylluteolin (swertiajaponin).

MICROSPECTROPHOTOMETRIC MEASUREMENT OF PH AND PH EFFECT ON COLOR OF PETAL EPIDERMAL-CELLS

Abstract A microspectrophotometric method has been developed for calorimetric pH determination using indicator dyes. Tissue samples as small as five cells were used. Measurements of standard buffered solutions of known pH were within a standard error of less than ± 0.04 pH units. Validity of the technique has previously been established by matching the pH values and absorption spectra of several model systems to that of living cells. A method for spectrophotometric pH determination of single cells is suggested. The pH change seemed to be the major factor in the color change in aging flowers. The epidermal pH, the absorption spectra of living tissue, the anthocyanidins, flavonols, and flavones present in more than 250 plants of many families were determined. These data indicate that pH is only one of numerous parameters determining flavonoid color in the living cell.

MEASUREMENT OF HEMOGLOBIN IN UNLYSED BLOOD BY NEAR-INFRARED SPECTROSCOPY

Visible and near-infrared transmittance (T) spectra of unlysed blood samples were obtained with an NIRSystems Model 6500 spectrophotometer modified for an open cell and a vertical light path. Without rigid control of the pathlength and temperature, we were able to measure hemoglobin content within a standard error of 0.43 g/dL using a single-term second-derivative ratio of log(1/T) data at 1740 and 1346 nm. Calibration was done on a set of 104 samples (two spectra of blood from 52 patients) having hemoglobin levels of 6.1 to 19.2 g/dL. Validation was done on an independent set of 56 samples (two spectra of blood from 28 patients) having hemoglobin levels of 7.2 to 19.0 g/dL. The reproducibility of the measurement, tested by computing the coefficient of variability of the 28 duplicated results, was 0.63% (<0.1 g/dL). The results demonstrate a rapid simple diffuse transmittance measurement of hemoglobin in unlysed blood.

Anthocyanin and pH in the color of ‘Heavenly Blue’ morning glory

Abstract The major anthocyanin in blue morning glory flowers, peonidin 3-(dicaffeylsophoroside)- 5-glucoside, is stable in a neutral aqueous solution and is solely responsible for the color of the flowers. Co-ocurring flavonols based on quercetin at the pHs of epidermal cells have no effect on the color of the anthocyanin. Deep or strong reddish-purple buds change to moderate or light blue open flowers within a 4 hr period, and during this time the pH of epidermal tissue increases from ca 6.5 to 7.5.

Direct spectrophotometric determination of moisture content of grain and seeds

The water absorption bands at 0.76, 0.97, 1.18, 1.45, and 1.94 μ were investigated for spectrophotometric measurement of the moisture content of grain and seeds. The spectral absorbance curve for a thin layer of ground wheat was measured for the 1.0- to 2.3-μ region, showing that the 1.94-μ band of water has a minimum of interference. Using a 2-gram sample of ground material mixed with 1.5 to 2.0 ml of carbon tetrachloride in a 4.4-cm diameter cell, the transmittance values of a large number of wheat, soybean, wheat flour, and wheat bran samples were measured at 1.94 and 2.08 μ. From these data, the optical density difference Δ OD (1.94–2.08) μ was computed for each sample and related to the moisture content as determined by standard procedures. Calibration curves obtained for each of the four materials showed standard deviations from 0.28 to 0.37 per cent moisture for the moisture range from 0 to 20 per cent. The water absorption band at 0.97 μ was measured on individual intact peanuts and related to the moisture content. A measurement within ±0.7 per cent moisture content was obtained, using Δ OD (0.97–0.90) μ as the measured value. The authors conclude that moisture determination by direct spectrophotometry is practical on grain and should be possible on a wide range of solids.