Volume 23, Issue 2

The preparation of 5 μ thick films of polystyrene selenonic and selenonous acids and their salts is described. Both acids are ion exchangers, the first with strong and the second with very weak acid groups. The IR spectra of these films, hydrated with H 2 O and D 2 O, are shown, and the bands of these spectra are assigned.

Electrical conductivity measurements were made for the determination of G (free ions) in some hydrocarbons. The radiation source was a x-ray tube operated at 55 kV. Four quantities were measured for each liquid: 1. the stationary electrical conductivity at low electric field strength during irradiation, 2. the mobilities of the radiation-induced ions, 3. the volume recombination coefficient, and 4. the absorbed dose rate. All measurements were performed with aerated liquids at room temperature. The following G-values were obtained: n-pentane 0,1; n-hexane and n-heptane 0,09; iso-octane 0,11; cyclohexane 0,06; benzene 0,07; decalin 0,04. The standard deviation was estimated to ± 25 per cent.

Durch Sublimation des grünen [ (π-Cyclopentadienyl) -chrom-tricarbonyl] 2 wurde bei 80 °K das monomere paramagnetische CpCr (CO) 3 erhalten. Aus den EPR-Spektren polykristalliner Proben berechnen sich drei Extremwerte des g-Faktors zu g 1 = 1,996, g 2 = 2,03 und g 3 =2,117, die eine gestörte Symmetrie des Moleküls beweisen. Bei der Sublimation mit Ferrocen resultieren zwei verschiedene paramagnetische Substitutionsprodukte, die sich vermutlich durch die Stellung des Substituenten am Ferrocen (Ring bzw. Metall) unterscheiden.

Es wurden die Extraktions- und Rückextraktionsbedingungen der Chloride von 228 Ra, 228 Ac, 212 Pb und 212 Bi mittels Säulenverteilungs-Chromatographie mit umgekehrten Phasen untersucht. Als Extraktionsmittel wurde Di (äthylhexyl) -phosphorsäure verwendet, die auf gepulvertem Polytrifluoro-monochloroäthylen adsorbiert war. Als Eluent diente Salzsäure verschiedener Konzentrationen. Die γ-Spektren von 226 Ra und 228 Ra wurden mit Hilfe eines Ge (Li) -Halbleiter-Detektors aufgenommen.

Chemische Verschiebungen von Phosphorkernen in Verbindungen mit Phosphor der Koordinationszahl 5 und 6 sowie in zahlreichen Phosphor-Stickstoff-Ringverbindungen sind tabellarisch zusammengestellt und werden z. T. diskutiert. In zwei Fällen wird eine 31 P- 1 H-Kopplung über drei Bindungen hinweg berichtet.

Micro determination of molybdenum (VI) with 7-phenylazo-8-hydroxyquinoline-5-sulphonic acid is described. Molybdenum (VI) forms yellow, water souble complex in the pH range 2.5 — 5.5. 1:1 (M:L) stoichiometry has been established by (i) JOB’s and (ii) molar ratio methods. The colour reaction is instantaneous and the colour intensity remains unchanged for about 24 hours. The Beer's law is obeyed from 0.2 to 8.0 ppm of molybdenum per ml. The molecular extinction coefficient of the complex has been found to be E 400 mµ =1.38 × 10 4 , giving Sandell's sensitivity coefficient 0.0069 μg of molybdenum per cm 2 . The values of formation constant (log K) and free energy of formation (JF°) obtained by three methods are 5.40 ± 0.3. 5.20 ± 0.15, 5.62 ± 0.03 and (-7.50 ± 0.40, —7.22 ± 0.20, —7.80 ± 0.04 K.cals) respectively. The interference due to a number of anions and cations in the determination of molybdenum (VI) has also been studied. Azoxine S dyes having the general formula: (where R represents substituted benzene ring) have been found to form yellow, water soluble complexes with a number of metal ions. The dyes have been mainly used as metal ion indicators in recent years 1—5 . However, a few physico-chemical studies on the complexation reactions of these dyes have also been reported 7—9 . In the present investigations, a detailed study of molybdenum (VI) complex of the 7-phenylazo-8-hydroxy-quinoline-5-sulphonic acid has been carried out and it has been shown to form 1:1 complex in the pH range 2.5 to 5.5. The reaction is quite sensitive and can be used for the micro determination of molybdenum (VI).

Anodic and cathodic half wave potentials of porphin, tetraazaporphin, Mg (II)-tetraazaporphin, uroporphyrin I and phtalocyanin were measured respectively calculated, and also the reduction potentials of pheophytin a and thioazacarbocyanines. These and the redox potentials of further porphins were compared with some of their photochemical reaction. It was found that the energy difference between the first excited state and ionization in photochemical active porphins are smaller than in less active dyes. An electron from the first excited state of chlorophyll a e. g. is 0,95 eV more easy removed than from phtalocyanin. The influence of metal ions in systems with Η-bonding, e. g. porphins, 8-oxychinolin and proteins will be discussed.

Η-bonding between Pyrrolidon and different aczeptors is investigated. Different attempts of mathematical refinements are not much better than the common corrections of the overlapping H-bond-band. Pyrrolidon shows in different solvents only a dimerisation. Therefore the selfassoziation of the donor can easy mathematically separated from the donor-aczeptor-interaction. The series different aczeptors gives small differences between the amidgroup as donor and phenol as donor. This sequence determined by the equilibrium constants with the overtone spectra is in the case of Pyrrolidon the same than the series determined by the frequency-shift of the H-bond-band in the fundamental region.

The formation of adducts of some 1,2-dithiacyclopenten-ones- (3) and -thiones- (3) as well their binary mixtures in benzene and cyclohexane resp. has been investigated by measurements of the apparent conductivity and molar polarization. A theory based on simple assumptions describes reasonable well the experimental run of the apparent conductivity of these binary mixtures. In addition these assumptions might give some hints on a possible mechanism of the charge production.

By measuring the 35 Cl nuclear quadrupole resonance (NQR) spectra it is shown that AsCl 3 , like SbCl 3 , is able to form crystalline complex compounds with aromatic hydrocarbons. Investigation of the freezing-point diagrams reveal the existence of the following compounds: 2 AsCl 3 · C e H 6 ; 2 AsCl 3 · C 10 H 8 ; 2 AsCl 3 · (C 6 H 5 ) 2 CH 2 ; 2 AsCl 3 · p-C 6 H 4 (CH 3 ) 2 ; 2 AsCl 3 · C 6 H 5 C 2 H 5 and AsCl 3 · C 6 H 5 C 2 H 5 . The 35 Cl NQR spectra of these compounds are given and compared with the NQR spectra of the analogous SbCl 3 -complexes.

Using a strain of Claviceps paspali Mar 488 it has been shown that alanine-2-C 14 is incorporated with high efficiency in the carbinol amide moiety of D-Lysergic acid-α-hydroxyethylamide=II. After feeding of ᴅʟ-alanine- 15 N, DL-aspartic acid- 15 N and ʟ-glutamine-CO- 15 NH 2 the highest specific incorporation rate was observed with DL-alanine- 15 N. Short term experiments with ᴅ,ʟ-alanine- 15 N revealed, that the greater part of the 15 N-excess is localized in the N-atom of the side-chain of II. The carbinolamide moiety of the isolated alkaloid arises probably from alanine or a closely related compound.

The presently accepted theory of nerve excitation (HODGKIN and HUXLEY, 1952) fails to explain the mechanism of regulation of the state of the axon membrane by the membrane-potential or the cation-activities. We have proposed a physico-chemical mechanism for the regulation of the excitation state based on a model of the axon membrane as a two-dimensional cooperative cation exchanger in contact with the electrolyte reservoirs inside and outside. In the resting state, the lattice units of the cation exchanger bind calcium ions. Upon depolarization or decrease of the calcium activity in the outside medium, the resting state becomes instabil and univalent cations are bound by the lattice units. The ion movements accompanying the cation exchange give rise to the inward excitation current, as observed in a voltage clamp experiment. This cooperative cation-exchange can be considered as a two-dimensional phase transition. Its kinetics have been described by the processes of nucleation and nucleus-growth. The kinetic theory has been applied to measurements of the ionic current in the voltage clamp experiments of COLE and MOORE (1960). The theory describes in good agreement with the experiment the dependence of the ionic current on time and on membrane potential for small depolarizations. Three parameters have to be adjusted in this comparison, two of which have a simple molecular meaning and are given as: a 0 = 21 × 21 Å 2 =area per lattice unit w = 5.1 Kcal/mol=twice the difference in interaction energy of a lattice unit in the two binding states with the rest of the lattice being in one of the two states. The order of magnitude of these parameters favours the hypothesis of identifying the excitable structural units in the axon membrane with membrane-bound proteins.

Frisch präparierte und in vitro neugebildete Polyribosomen werden 10 min bei 22 °C der Einwirkung von RNase, Trypsin und α-Chymotrypsin unterworfen. Die frisch präparierten Polysomen werden durch RNase und Trypsin in die 78 S- und 105 S-Einheiten zerlegt. In vitro neugebildete Polysomen werden nur durch Trypsin angegriffen. α-Chymotrypsin zeigt sowohl bei den frisch präparierten als auch bei den in vitro neugebildeten Polysomen keinen Effekt auf die Verteilung der Polysomen im Saccharose-Dichtegradienten. Ein Einfluß der nascierenden Peptidketten auf die Polysomenstruktur wird nicht gefunden. Eine Stabilisierung der mRNS durch basisches Protein wird angenommen.

Bei der in vitro-Proteinsynthese mit pH 5-Überstand, tRNA und Cysteamin an Leber-Polyribosomen wird in Gegenwart von Leberzellkern-Fraktion eine Neusynthese von Polyribosomen beobachtet. Ein Übertritt der Orotsäure-6- 14 C in vivo markierten mRNS und des 3 H-1-Arginin markierten Kernprotein vom Kern auf die Ribosomen bzw. Polysomen kann gezeigt werden. Polyribosomen, die vor der in vitro-Proteinsynthese 10 min bei 35 °C erwärmt werden, zeigen eine verminderte Anlagerung von mRNS und Kernprotein und eine Reduzierung der Proteinsynthese. Die Diskussion ergibt, daß eine Stabilisierung der mRNS durch Kernprotein angenommen werden kann.

1. Der Einfluß von Fermentinhibitoren auf den 32 P-Einbau in Mykobakterien unter Bedingungen der endogenen Atmung wird untersucht. 2. Arsenal stimuliert bei niedrigen Inhibitor-Konzentrationen den 32 P-Einbau. Bei Erhöhung der Hemmstoffkonzentration wird die Incorporation des radioaktiven Isotopes durch die untersuchten Fermentinhibitoren gehemmt. 3. Ähnliche Ergebnisse werden auch beim Einsatz von antituberkulös wirksamen Stoffen erhalten. So bewirken z. B. niedrige Konzentrationen von Äthioniamid eine Stimulierung, höhere Konzentrationen eine Hemmung des Einbaues. 4. Für Isoxyl läßt sich eine eindeutige Wirkung nachweisen. Sie entspricht in ihrer Beziehung zur Konzentration der des Äthioniamides. Die Wirkung von Ethambutol ist abhängig von der Incubationsdauer. 5. Sensible und resistente Bakterien verhalten sich unterschiedlich gegenüber dem die Resistenz verursachenden Mittel. Der 32 P-Einbau in die resistente Population wird kaum beeinflußt. 6. Auf Grund dieses Verhaltens wird eine Differenzierung zwischen sensiblen und resistenten Keimen versucht. Die optimalen Reaktionsbedingungen werden festgelegt. 7. Die für INH und Sm erhaltenen Ergebnisse werden denen gegenübergestellt, die mit mikrobiologischen Verfahren erhalten wurden. Das Verfahren wird zur raschen Resistenzbestimmung vorgeschlagen.

An UDP-activated murein precursor was isolated from Butyribacterium rettgeri after one hour inhibition by D-cycloserine. The compound contains UDP, muramic acid, L-serine, D-glutamic acid and L-ornithine in equimolar amounts. The amino acid sequence of the tripeptide attached to muramic acid is L-Ser-D-Glu-L-Orn as determined by end group analysis and identification of peptides obtained after partial hydrolysis. As shown by the identification of glutamic acid -γ-hydrazid after hydrazinolysis of the compound, ornithine is bound by its α-amino group to the γ-carboxyl group of glutamic acid. The amino acid sequence of the precursor is in agreement with the structure of the corresponding part of the whole murein of Butyribacterium rettgeri, as proposed recently.

Plastoquinone PQ is engaged in photosynthesis 1 . Difference spectra in the UV-region indicate that PQ is an intermediate in the electron transport chain 2 . PQ is located as a pool between the two light reactions I and II 3 . PQ is reduced by hν II and oxidized by hν I 3 . In this paper the difference spectra which occur during light excitation of spinach chloroplasts and chlorella vulgaris were measured in the UV-region with high resolution by the high sensitive method of periodical flash photometry 6 . On excitation with long flashes (10 —1 sec) the difference spectra are similar to those obtained when plastoquinone is reduced to hydroquinone in vitro (see figs. 1, 3 and 6). Deviations in the case of chlorella (fig. 4) are caused by additional NADP-reduction. After extraction of plastoquinone from chloroplasts the difference spectra do not occur during light excitation but they can be produced in full after reconstitution with synthetic plastoquinone A (see fig. 2). In the presents of far red background light (718 nm) which excites only light reaction I the magnitude of the spectrum is doubled (see fig. 3). By excitation with short flashes (10 —5 sec), two different spectra were found. The difference spectrum with a life-time of 5 · 10 —4 sec (fig. 7) is new and does not correspond to that of plastoquinone in vitro. The difference spectrum with a life-time of about 2·10 —2 sec (fig. 5) corresponds to the plastoquinone reduction. The magnitude of this spectrum is ten times smaller than that obtained by excitation with long flashes (fig. 6). The 1:10 ratio of the magnitude of the spectra in short and long flashes can be interpreted by a pool of plastoquinone between the two light reactions with a dynamic capacity of ten electrons. The doubled magnitude of the spectra in far red background light can be interpreted by an electron acceptor pool for plastoquinone with a capacity of five electrons (see also the following papers).

The absorption changes at 254 nm which are coupled with the formation of plastohydroquinone (PQ = ) depend strongly on the intensity and duration of the actinic light (fig. 2). At an intensity of 10 6 erg·sec -1 ·cm -2 and a duration of 0,1 sec, maximal reduction is obtained. The reduction of chlorophyll-ai ° was followed by absorption changes at 703 nm. From the changes at 254 and 703 nm (fig. 3 and tab. 1) follows: PQ=: Chl-a I = 5:1 (with Δε = 1,3·10 4 l · Mol- 1 · cm -1 for PQ at 254 nm and Δε = 3,6 · 10 4 l · Mol -1 · cm -1 for Chl-a I at 703 nm). This value corresponds to a pool of plastoquinone with a dynamic capacity of ten electrons. This value is exactly the same as that which was derived in another way in the preceding paper 3 . The time course of the reduction of plastoquinone is given by an exponential function (figs. 4 and 5) with a rate constant for the reduction k 1′ = 35 sec -1 at 25 °C. Together with the rate constant for the reoxidation (k 2 ′ = 11 sec -1 , see next paser 6 ), it follows for the total photochemically engaged plastoquinone PQ 0 : Chl-a I = 6.5: 1.

After the reduction of PQ in the light, PQ = is oxidized in the dark. Three types of reoxydation can be distinguished in isolated chloroplasts of spinach: a) Without addition of an electron acceptor: No reoxidation can be observed (fig. 1 a). b) With addition of an electron acceptor: 50% is reoxidized (fig. 1 b). c) With addition of an electron acceptor and permanent far red background light (718 nm) 50% is reoxidized as in b, the other 50% are oxidized in a second phase (see fig. 1 c). This second phase depends on the intensity of the far red background light (figs. 4 and 5). The reoxidation at the time t′ (see fig. 2) follows (d[PQ=]/dt) t´ = — k 2 ´[PQ=] (fig. 3) with k 2 ´=11 sec -1 at 25 °C. The kinetics can be interpreted by assuming a pool of PQ between the two light reactions I and II with a dynamic capacity for ten electrons, and an electron acceptor pool U with a capacity for five electrons (see figs. 7, 8 and 9). Members of U are chlorophyll-a l , cytochrome-f and three unknown intermediates. The kinetics should depend on the redox state of these pools. The path and reaction times of the electron flow between the two light reactions are depicted in fig. 13. The phenomena described for isolated chloroplasts appear also for whole chlorella cells (fig. 10). In chlorella the electron acceptor is formed by hv I -light in >0,5 sec. K-ferricyanide has a special function among the electron acceptors. On the addition of K-ferricyanide (>10 -4 Mol/l) plastoquinone which is reduced in long flashes is completely oxidized without far red background light (fig. 11). This indicates that the electrons produced in long flashes are removed from the chain by K-ferricyanide at U (see fig. 12).

By excitation of spinach chloroplasts with flashes (5 · 10 -5 sec) of far red light hvI (λ=728 nm) and with addition of 2·10 -4 M/I benzylviologen as electron acceptor irreversible absorption changes are observed as depicted in fig. 1 top. With 10 -3 M/l K 3 Fe (CN) 6 as electron acceptor irreversible changes are observed as depicted in fig. 1 bottom. The difference of the spectra in fig. 1 is presented in fig. 2. Fig. 2 corresponds to the spectrum which is caused by reduction of a cytochrome-b-563. Thus excluding K 3 Fe (CN) 6 as electron acceptor cytochrome-b-563 can be reduced by hvI (λ=728 nm). A re-oxydation occurs by red light hvII (λ = 663 nm), s. figs. 3, 4. These results demonstrate a natural cyclic flow of electrons including both light reactions Chl-ai and Chl-aII (s. fig. 6). The results are reviewed in 1. c. 10 .

Carefully prepared spinach chloroplasts show the slow phase (half life 20 — 500 msec) of the absorption changes of Chlorophyll-b only. The decay of the absorption changes is an exponential one (fig. 1, fig. 5, eq. 1). The decay time as well as the electron transport rate are changed by coupling and uncoupling phosphorylation. A. By addition of the phosphorylation uncoupler methylamine hydrochloride the decay is accelerated up to ten times from 500 msec to 50 msec at pH = 7,4 and 20 °C (fig. 1, table 1). At the same time the electron transport rate measured by the reduction of ferricyanide increases ten times (table 1). Reciprocal decay time and electron transport rate are always proportional to each other (fig. 2, eq. 2). Phosphorylation uncouplers as carbonyl cyanide phenylhydrazone, atebrin, and dichlorphenol indophenol accelerate the decay of the Chl-b absorption changes as well (fig. 3). B. Phosphorylation accelerates the decay time of the Chl-b absorption changes up to two times from 90 to 40 msec at pH=8,4 and 20 °C (fig. 4, fig. 5, table 2). At the same time the electron transport rate too increases two times, thus reciprocal decay time and electron transport rate are proportional to each other again (fig. 6, table 2). The same result is obtained when phosphorylation is suppressed by omission of phosphate or addition of phlorizin (fig. 6, fig. 7 top). It is shown that the phosphorylation rate is identical with the extra electron transport rate stimulated by phosphorylation as measured by IZAWA et al. 18 (fig. 7 bottom). At the same time it is shown that phosphorylation is proportional to the change in the reciprocal decay time of the Chl-b absorption changes (fig. 7 bottom, eq. 3). JUNGE and WITT 3 show that the slow phase of the Chl-b absorption changes are connected with the translocation of protons across the thylakoid membrane. In connection with those results phosphorylation is coupled to an additional proton transfer. The foregoing results are discussed in this respect in 1. c. 3 . The results are in part reviewed in *.

1. The Chl-b reaction in chloroplasts is biphasic. 2. Both the slow phase (~ 10 -1 sec) and the fast phase (≪ 10 -1 sec) are caused by ion exchange across the thylakoid membrane. 3. The slow phase is caused by an intrinsic slow ion exchange (H ® ) across an undamaged membrane (The permeability for arbitrary ions is lower than for H ® ). 4. The fast phase is caused by an enhanced ion exchange across a damaged membrane. Damaging can be systematically caused, for instance, by membrane holes made by osmotic procedures, or by specific pores for alkaline ions made by gramicidin. 5. The function unit of the intrinsic slow ion exchange (H ® ) has been identified as being the membrane of one whole undamaged thylakoid. 6. The electron transport in undamaged thylakoid membranes is coupled to the intrinsic ion transport (H®). 7. Phosphorylation is coupled to an additional intrinsic ion transport (H ® ). 8. Leaks of the order of only one pore cause a collapse from the intrinsic slow phase (10 -1 sec) into the fast phase of ion exchange (< 10 -1 sec). 9. The ratio of the amplitude of the slow and fast phases indicates the ratio of thylakoids which are undamaged and damaged. 10. The Chl-b reaction indicates an electrical field across the thylakoid membrane. This field promotes the ion exchanges discussed above. 11. The potential difference amounts to about 250 mV. 12. The field is built up in light within ≤ 2·10 -8 sec 29, 30 . 13. These results give a first direct insight into the properties of membranes on a molecular level. They serve as a valuable means for deciding between the different hypotheses on the mechanism of phosphorylation.

Tumorgewebe wird mangelhaft mit Sauerstoff versorgt. Bei der i. v. Injektion von anaerob auskeimenden Sporen von Clostridium butyricum finden daher die Sporen nur im Tumorgewebe einen geeigneten Nährboden. Mit Hilfe Tumor-tragender Ratten wurde daher untersucht, ob bei der i. v. Injektion von 51 Crmarkierten Sporen sich eine bevorzugte Sporen- und damit Aktivitätsanreicherung im Tumorgewebe im Vergleich zum Normalgewebe feststellen läßt. Entsprechende Verteilungsstudien wurden in vivo durch Szintigraphie und nach Töten der Versuchstiere durch Aktivitätsmessung in den einzelnen Organen ausgeführt. Die Ergebnisse zeigen eine bevorzugte Aktivitätsanreicherung im RES. Der zentrale nekrotische Bereich der Tumoren besaß eine erhöhte spezifische Aktivität gegenüber den Tumorrandgebieten.

The biosynthesis of 5-hydroxy-1,4-naphthoquinone (juglone) was studied by supplying radioactive precursors to leaves of Juglans regia plants. A chemical degradation of the juglone molecule was devised (Fig. 1). With these methods it was shown that the ring atoms of shikimic acid are incorporated into the benzene ring of the quinone, while the carboxyl group of this acid is transformed to 50% into each of the keto groups of the quinone ring (C-atoms 1 and 4 of juglone. Tab. 3). This suggested a symmetrical molecule to be an intermediate in the formation of juglone — most probable 1,4-naphthoquinone. This compound was synthetized with 14 C in the positions 2, 3, 9, and 10 and was found to be a good precursor of juglone in Juglans as well as for 2-hydroxy-1,4-naphthoquinone in Impatiens plants (Tab. 4) . 3,4-Dihydroxybenzaldehyde (Tab. 2) and chorismic acid (Tab. 7) which have been suggested previously as intermediates in the biosynthesis of naphthoquinones are no precursors of juglone. The source of three carbon atoms of the quinone nucleus remains to be determined; one or two of these carbon atoms (C 2 and/or C 3 of juglone) are formed from the methylen carbon of malonate (Tab. 5 and 6); surprisingly, however, the carboxyl carbons of malonic acid are not incorporated. The substitution of shikimic acid occures in the position 6 of this acid as could be judged from the degradation of juglone labelled with shikimic acid [ 1,2- 14 C] (Fig. 2; Tab. 3). 1,4-Naphthoquinone (or naphthohydroquinone) is postulated as an important intermediate in the biosynthesis of naphthoquinone derivatives in higher plants.

When the centric diatom Cyclotella cryptica is grown in a Si (OH) 4 -free medium, the glutamic acid pool decreases within 3 hours to a third of the original value, whereas the aspartic acid pool is reduced by only about 20 per cent. The pools of nucleosid-triphosphates and of glycerol-1-phosphate remain unaffected during this time. The nucleosid-diphosphates pool decreases in the same way as that of aspartic acid. The decrease in the glutamic acid pool precedes the inhibition of total protein synthesis in Si (OH) 4 -deficient cells, and a significant decrease in the a-ketoglutarate pool precedes the decrease of the glutamic acid content. Already within 60 minutes ofter incubation in a Si (OH) 4 -free medium, the content of a-ketoglutarate is decreased to one third of the normal value. On the other hand, the acetyl CoA pathway (enhanced fatty acid synthesis) is not inhibited. The results suggest, that the Si (OH) 4 -metabolism interferes with reactions between the condensing enzyme (acetyl-CoA and oxalacetate) and a-ketoglutarate. The delay between inhibition of protein- and RNA-synthesis and the different changes in the pools of amino acids and nucleosid-triphosphates resemble the regulation of the nucleosid-triphosphate pool and RNA-synthesis in amino acid starved strains of E. coli (EDLIN and NEUHARD) 1 , though the primary causes are quite different.

Cellulose microfibrils from the cell wall of the green alga Valonia macrophysa were isolated by enzymatical digestion of the wall matrix and examined in the electron microscope using the negative staining technique. The smallest fibrils obtained after prolonged treatment were found to be flat ribbons with a width about 10—20 nm and a height of 3 to 4 nm. This result is discussed in relation to Frey- Wyssling's concept of an “elementary fibril“ with a cross-section of 3.5 × 3.5 nm. Some alternation of unstained areas along the fibrils was observed. This was interpreted as artificially induced rather than relating to the structure and the arrangement of the cellulose chain molecules.