Modern methods of plant analysis
01 Jan 1964-
About: The article was published on 1964-01-01 and is currently open access. It has received 1991 citations till now.
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TL;DR: This work shows that the tobacco (Nicotiana tabacum) plasma membrane and inner chloroplast membranes contain the aquaporin Nt AQP1, which opens new opportunities for mechanistic examination of leaf internal CO2 conductance regulation.
Abstract: Photosynthesis is often limited by the rate of CO2 diffusion from the atmosphere to the chloroplast. The primary resistances for CO2 diffusion are thought to be at the stomata and at photosynthesizing cells via a combination resulting from resistances of aqueous solution as well as the plasma membrane and both outer and inner chloroplast membranes. In contrast with stomatal resistance, the resistance of biological membranes to gas transport is not widely recognized as a limiting factor for metabolic function. We show that the tobacco (Nicotiana tabacum) plasma membrane and inner chloroplast membranes contain the aquaporin Nt AQP1. RNA interference–mediated decreases in Nt AQP1 expression lowered the CO2 permeability of the inner chloroplast membrane. In vivo data show that the reduced amount of Nt AQP1 caused a 20% change in CO2 conductance within leaves. Our discovery of CO2 aquaporin function in the chloroplast membrane opens new opportunities for mechanistic examination of leaf internal CO2 conductance regulation.
286 citations
01 Jan 1975
TL;DR: The modern antibiotic era can be said to have opened on February 12, 1941, with the first clinical trial of penicillin, shortly followed by the introduction of one after another of the major antibiotic substances which remain the mainstay of clinical therapy of infectuous diseases to this date.
Abstract: The modern antibiotic era can be said to have opened on February 12, 1941, with the first clinical trial of penicillin. Within a couple of years man had at last, after eons of adventitious searching, a truly effective and safe agent for the treatment of many systemic bacterial infections. This was shortly followed by the introduction of one after another of the major antibiotic substances which remain the mainstay of clinical therapy of infectuous diseases to this date. Intensive screening of fermentation liquors derived from various microbes, principally fungi and streptomycetes, has resulted in literature descriptions of more than 2,000 Individual antibiotics to date, and It has been estimated that more than 20,000 analogs of 6-amino- penicillante acid alone have been made by chemists working tn close collaboration with biochemists and microbiologists. Several of these substances are currently on the market.
284 citations
TL;DR: Pollen odors are more pronounced in insect- than bird- or wind-pollinated plants, suggesting that volatile emission evolved in part under selection to attract pollinators and increase its dispersal by animals.
Abstract: The literature is reviewed and new evidence presented that pollen produces odors, which serve multiple functions in pollination and defense. Pollen odor, which originates from pollenkitt, comprises volatiles that belong to the same chemical classes found in flower scents, that are in species-specific mixtures, and that contrast with odors of other floral parts. Pollen can also take up volatiles from surrounding floral odors, but this adsorption is selective and varies among species. Pollen odors are more pronounced in insect- than bird- or wind-pollinated plants, suggesting that volatile emission evolved in part under selection to attract pollinators. Pollen-feeding insects can perceive pollen odor and use it to discriminate between different pollen types and host plants. Pollen odor influences bee foraging, including the location of pollen sources, discrimination of flowers with different amounts of pollen, and host-plant recognition by pollen-specialist species. In the few wind-pollinated plants studied, odors of male flowers or pollen are comparatively high in a-methyl alcohols and ketones; these volatiles may serve in pollen defense, with some known to repel insects. Pollen odor often includes chemicals with documented defense activity, which is probably aimed mainly at nonpollinator pollen-feeding insects and pathogens; an involvement in pollen allelopathy is also possible. Pollen volatiles comprise chemically diverse compounds that may play multiple roles, and their emission in pollen odor undoubtedly evolved under the principle, and often conflicting, selective pressures to both protect the male gametophyte and increase its dispersal by animals.
283 citations
TL;DR: The composition of the wall of each form was found to be constant, irrespective of growth conditions, except for some variation in the amounts of mannose and glucose in wall hydrolysates.
Abstract: SUMMARY: Cell walls were obtained from the mycelial and blastospore forms of Candida albicans; these were delipidized and separated into alkali-soluble and alkali-insoluble fractions. The detailed composition of these fractions was determined in organisms grown on different media at 37° and on the same medium at different temperatures (blastospores 30°, mycelium 40°). The composition of the wall of each form was found to be constant, irrespective of growth conditions, except for some variation in the amounts of mannose and glucose in wall hydrolysates. The alkali-insoluble fraction from the mycelial form contained 3 times as much chitin as that from blastospores and only about one third as much protein. The protein from these two fractions showed marked differences in amino acid composition. Differences between the two morphological forms in the amounts of carbohydrate and protein in the alkali-soluble fractions were also found. The results are discussed in relation to other studies of cell-wall composition in the dimorphic
280 citations
TL;DR: A directly proportional relationship was found between protein content and the increase in salt concentrations in the first measurement period, while it was inversely proportional in the second.
275 citations
References
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01 Jan 1963
TL;DR: In this article, a physiologischer Vorgang auf eine enzymatische Wirkung zuruckgefuhrt werden (vgl. S. 301), besteht die folgende Aufgabe darin, Naheres uber die Eigenschaften des beteiligten Enzyms zu ermitteln.
Abstract: Kann ein physiologischer Vorgang auf eine enzymatische Wirkung zuruckgefuhrt werden (vgl. S. 301), so besteht die folgende Aufgabe darin, Naheres uber die Eigenschaften des beteiligten Enzyms zu ermitteln. Hierzu gehoren die Bestimmung der Reaktions- und Substratspezifitat sowie die Ermittlung der Bedingungen, unter denen eine optimale Wirkung des Enzyms gegeben ist. Wesentlich zur Charakterisierung ist ferner die Untersuchung der Stabilitat des Enzyms und dabei insbesondere die Feststellung, ob es sich um ein Ferment handelt, das zur vollen Aktivitat dialysable Cofaktoren benotigt. Falls diese Frage bejaht wird, ist auch die Bestimmung der unerlaslichen Cofaktoren anzuschliesen. Uberdies bietet auch der Nachweis der Lokalisation des Enzyms in der Zelle (oder im Zellverband) eine entscheidende Moglichkeit zur Charakterisierung des Fermentes. Hinzu kommt schlieslich noch die Untersuchung der Wirkung einzelner Inhibitoren1 auf das Enzym, die zu weitgehender Klarung des Reaktionsmechanismus beitragen kann und eine Abgrenzung der Eigenschaften des untersuchten Fermentes gegenuber ahnlichen Enzymen erlaubt.
2 citations
01 Jan 1962
TL;DR: Optical rotation has been found to be one of the most convenient methods of following the denaturation of proteins and rotatory dispersion is capable of providing information on the folding of the polypeptide chain in proteins and the changes accompanying denaturation.
Abstract: Optical rotation has been found to be one of the most convenient methods of following the denaturation of proteins. Generally speaking denaturation can be defined as a process or sequence of processes in which the spatial arrangement of the polypeptide chains within the molecule is changed from that typical of the native protein to a more disordered arrangement (Kauzmann 1959). The terms “configuration”, “conformation” and “state of folding” are widely used for spatial arrangement. It is probably best to follow the suggestion of Blout (1960) and restrict the use of “configuration” to its original sense, i.e. the spatial arrangement around an asymmetric carbon atom, and to use “conformation” for the shape of the molecule in its entirety. The properties discussed in the previous Chapter i.e., viscosity, diffusion, sedimentation, and light scattering — can all furnish information on the overall shape of proteins or other macromolecules and changes in this shape with environment. Thus Doty, Bradbury and Holtzer (1956) were able to show using these methods, together with streaming birefringence, that poly-γ-benzyl-L-glutamate could exist in two conformations, the α-helix and the solvated randomly coiled form, depending on the solvent. The change from α-helix to random coil was accompanied by marked changes in the optical rotatory properties of the polypeptides. It is to be expected that an α-helical structure should contribute to the rotatory power of a polypeptide since helices are asymmetric and not superimposable on their mirror images. The work on polypeptides has shown that rotatory dispersion is capable of providing information on the folding of the polypeptide chain in proteins and the changes accompanying denaturation.
1 citations