Total chlorophyll

Chlorophyll b occurs as an accessory pigment of the light-harvesting systems in land plants and green algae, and comprises one-third (or less) of total chlorophyll. The biosynthesis of chlorophyll b has been an area of active research particularly regarding its compartmentalization in chloroplast membranes, identification of the gene for chlorophyllide a oxidase, and characterization of the enzymes involved. ... 

The wide distribution of chlorophylls throughout the plant kingdom facilitates the scrutiny of chlorophyll-rich vegetables for human nutrition with a view to their direct consumption. However, until now, little standardized information was available in the literature regarding the absolute total chlorophyll contents and the ratios of chlorophylls a and b in raw materials. The different analytical methods of extraction and quantification and the lack of data about moisture contents (that may vary considerably among varieties and preparations) can also influence the final contents of pigments. These factors have largely contributed to the discrepancies found in similar food samples. 

Total Chlorophyll Contents of Some Vegetables and Fruits... 

The equations (1 through 3 below) of the official method for total chlorophyll, chlorophyll a, and chlorophyll b analysis of plants published as Method 942.04 by... 

Zhuang H, Barth MM and Hildebrand DF. 1994. Packaging influenced total chlorophyll, soluble protein, fatty acid composition and lipoxygenase activity in broccoli florets. J Food Sci 59(6) 1171-1174. 

Part B Quantitative Determination of Total Chlorophyll in Spinach Leaves... 

Total carotenoid Total Chlorophyll (a b) Total Chlorophyll-a Total Chlorophyll-b Poly phenols Catechins... 

PIGMENT RATIOS TO THE TOTAL CHLOROPHYLL-A FOR EIGHT TAXONOMIC GROUPS BASED ON CHEMTAX ANALYSIS... 

A widespread method for determining the induction period for autoxidation of oils and fats consists of passing a continuous stream of air through the heated sample and collecting the volatile acids evolved in a water trap, where they are determined on a real time basis. The time plot usually presents a flat appearance for a certain period and then takes off in an accelerated manner. This test is the basis of several national and international standards (e.g. AOCS Cd 12b-92—oil stability index" ISO 6886—accelerated oxidation test for oxidative stability of fats and oils ) and the design of the Rancimat equipment, where the end determination is based on conductivity measurements . In addition to oxidation stability as determined by the Rancimat method and POV, which negatively affects virgin olive oil stability, other nonstandard properties were proposed for better assessment of the quality of this oil, namely LC determination of Vitamin E (21), colorimetric determination of total polar phenols and UVD of total chlorophyll. ... 

Chloroplasts will be isolated by careful extraction of spinach leaves, using tricine buffer containing sucrose. The crude extract contains both whole and fragmented chloroplasts, but both contain all the necessary photosyn-thetic components and are capable of photophosphorylation. The preparation described in this experiment retains almost all of the chlorophyll in the chloroplasts. The total chlorophyll content of the chloroplasts will be determined by extracting the pigment with aqueous acetone and measuring the absorption at A. = 652 nm. The chlorophyll concentration is calculated according to Equation E9.3 (Arnon, 1949),... 

AOAC (Association of Official Analytical Chemists) International 1995. Method 942.04 Chlorophyll in plants Spectrophotometric method of total chlorophyll and the a and b components. In Official Method of Analysis, 16th ed. AOAC International, Arlington, Va. 

Pigment levels given in mg/m2 leaf area and in mg/g dry weight (dw). Values measured are those from fully developed leaves in June, 2000. Pigment levels within one leaf usually vary by <3%, and pigment ratios vary by <1%. Abbreviations a + b total chlorophylls a and b x + c, xanthophylls and carotenes (total carotenoids). 

The literature search was now expanded and yielded the conclusion that another possible and more widespread precursor is the light-harvesting chlorophyll a/b-protein (LHCP), which is present in almost all photosynthetically grown higher plants and green algae (ref. 373-375). It is by far the major pigment-protein in these plants and accounts for 40-60% of the total chlorophyll (ref. 373,374). 

Chlorophyll was extracted from 40 mg of leaf tissue per treatment in 3 mL of dimethyl sulfoxide.19 Total chlorophyll concentration was determined spectrophotometrically according to Arnon2 measuring optical absorbance at 645 and 663 nm. 

The chlorophyll concentration in the leaves varies among clones, with the sum of chlorophyll a and b ranging from 0.3 to 0.6 g nr2 (Soja and Haunold, 1991). The ratio of chlorophyll a to h is similar across clones (i.e., 70 to 72% chlorophyll a, 28 to 30% chlorophyll b). Elevated chlorophyll content appears to be related to increased photosynthetic rate in some clones, as indicated by a positive correlation between photosynthetic rate and total chlorophyll content (a + b) (r = 0.71). Thus, clones with improved photosynthetic capacity could potentially be obtained by selecting for high chlorophyll. 

FIGURE 5. Model for the organisation of photosy stem I in barley, showing the disttribution of chlorophy 11 a and b between the different chlorophyll-proteins. Over half of the total chlorophyll is in LHCI, and LHCI-680 is postulated to mediate excitation energy transfer from LHCII, when LHCII becomes phosphorylated and migrates from appressed to non-appressed membranes. 

Fig. 3b, the majority of total chlorophyll associated with a Phaeocystis colony can be derived from diatoms on the colony rather than Phaeocystis cells within the colony. Therefore to accurately quantify Phaeocystis biomass, particularly during intense and prolonged blooms, it is necessary to... 

Specific phytoplankton growth rate (jx) is also shown. All rates are quantified by the dilution technique (Landry and Hassett 1982). Prey concentrations were analyzed by cell counts, total chlorophyll a fractions (Total Chi a), high-performance liquid chromatography (HPLC), or flow cytometry (FC)... 

Aiken, J. A feasibility study for the design and development of a total chlorophyll sensor Inst, tor Mar. Environ. Res., unpublished report, 1980. Yentsch, G. S. Deep-Sea Res. 1960, 7, 1-9. 

Using the known extinction coefficient of 32 mM cm" at the peak of red band for pheophytin in solution, the amount ofpheophytin undergoing photoreduction relative to total chlorophyll is estimated to be 1/30-40. Since the Chl/P680 ratio in TSF Ila is known to be -40/1, the reactant P680/[Pg.308]

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