bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aktive Aufnahme von Zuckern durch Zellen von Neurospora crassa unter Beteiligung eines enzymatischen Systems mit Permease-Eigenschaften II
Authors: Klingmüller Walter 
Published: February 2015

Sorbose-transport in Neurospora has been investigated further. Methods and results were as follows:
Conidia pregerminated with fructose were incubated with increasing amounts of 14C-labelled sorbose, their radioactivity was measured by millipore-filter technique. Sorbose uptake followed Michaelis-Menten kinetics, with Km = 5.1 ± 1.2 mM and Vmax=0.16 ± 0.05 mg sorbose/mg dry weight/minute. It was inhibited slightly by addition of fructose, and strongly by addition of glucose; the exact type of inhibition was concentration dependent.
Ungerminated conidia or pregerminated conidia were incubated with 14C-labelled sorbose. A base level of sorbose uptake by ungerminated conidia, and an increasing uptake with increasing pregermination time of the conidia was found; the uptake was proportional to germ-tube length.
Supernatants of ungerminated or germinated conidia were checked for sugars related to sorbose by enzymatic and bio-assays. The results were negative.
Radiopaperchromatography of aqueous extracts of incubated conidia revealed that sorbose as opposed to fructose is not phosphorylated during uptake, but accumulated as the pure sugar inside the cells. Ca. 90% of the fructose but barely 7% of sorbose taken up is transformed into a water insoluble form after 60 minutes incubation of the conidia.
Conidia incubated with labelled sorbose were treated with unlabelled sorbose or Na-azide. The accumulated labelled sorbose was driven out by both treatments (with sorbose ca. 65% with Naazide ca. 80% after 60 minutes).
The data support the hypothesis proposed earlier1 that sorbose is taken up into conidia of Neurospora crassa by means of active transport, mediated by an inducible enzymatic system of the permease-type.
Untersuchungen über den Einbau methylierter Vorstufen in die Isoflavone der Kichererbse
Authors: Barz Wolfgang , Grisebach Hans 
Published: February 2015

In order to determine at what stage in the biosynthesis of biochanin A (5.7-dihydroxy-4′-methoxyisoflavone) and formononetin (7-hydroxy-4′-methoxyisoflavone) the methylation of the 4′-hydroxygroup occurs, the incorporation of p-methoxy-cinnamic acid-[3-14C-methyl-T], 4-methoxy-2′.4′-dihydroxychalcone- [β-14C-methyl-T] and a number of unmethylated precursors into the isoflavones of chana seedlings (Cicer arietinum L.) was compared. p-Methoxy-cinnamic acid and 4.2′.4′-Trihydroxychalcone were found to be the best precursors. Although the incorporation of p-methoxy-cinnamic acid was very good (incorporation rate 6.2%) the T/14C ratio dropped by 95% upon incorporation into the isoflavones, a fact which showed that a rapid demethylation takes place in the plants.In addition, kinetic experiments were carried out with p-methoxycinnamic acid- [3-14C-methyl-14C-methyl-T] and 4-methoxy-2′.4′-dihydroxychalcone- [β-14C-methyl-14C-methyl-T]. But in this case also the rapid demethylation did not permit a definite conclusion to be drawn as to the stage in the biosynthesis at which the methylation step occurs. The very good incorporation of 4.2′.4′-trihydroxycalcone- [β-14C] into the isoflavones (5,3% incorporation, dilution 61), however, shows that methylation can occur at a late stage in the biosynthesis.
Zur Biosynthese des Apigenins und Chrysoeriols in der Petersilie
Authors: Grisebach Hans , Bilhuber Wolfgang 
Published: February 2015

The aglykon of a second flavoneglycoside present in parsley plants and fruits has been identified as Chrysoeriol (5.7.4′-trihydroxy-3′-methoxyflavone). According to its hydrolytic and spectral properties the glycoside is the 7-apiosyl-glucoside of chrysoeriol.
4.2′.4′.6′-Tetrahydroxychalcone-2′-glucoside- [β-14C] is incorporated into apigenin (5.7.4′-trihydroxyflavone) in parsley without randomization of the label.
When a mixture of 5.7.4′-trihydroxyflavanone-[2-14C] with either trans-3.5.7.4′-tetrahydroxyflavanone- [T] or 3.5.7.4′-tetrahydroxyflavone- [T] was fed to two month old parsley shoots, the incorporation of the trihydroxyflavanone into apigenin or chrysoeriol was higher by a factor of 67 to 400 than that of the tetrahydroxyflavanone or tetrahydroxyflavone. These results prove that the flavones are formed by dehydrogenation of flavanones and not by dehydration of dihydroflavonols.
Kern- und Nucleolusausbildung in den Gametophytenzellen von Dryopteris filix-mas (L.) Schott bei Umsteuerung der Morphogenese
Authors: Bergfeld Rainer 
Published: February 2015

The young gametophytes of the fern Dryopteris filix-mas (L.) SCHOTT have different metabolic patterns in red and blue light with blue favouring protein formation. In connection with this, the morphogenesis is also different. Two-dimensional prothallia are developed in blue light; in red light, however, the gametophytes grow as filaments. In the present paper the influence of red and blue radiation upon the size of the nuclei and nucleoli has been studied in fully differentiated stable basal cells and actively dividing apical cells. Time course studies revealed that the apical cell of the red form always contains extremly large nuclei and nucleoli. This is in agreement with high synthetic activity of this cell. In contrast, the apical cells with two cutting faces of the blue grown gametophytes have much smaller nuclei and nucleoli (this may be due to the comparativly high dividing activity of this cells). In already differentiated basal cells, these two organelles are even smaller and show only minor differences between red and blue ones. Within the gametophytes there is a gradient in the nucleus and nucleolus size from the apical to the basal cells.
If blue grown gametophytes are brought into red light, or vice versa, typical changes in size of the nucleus and nucleolus in the direction of the respective forms are already visible after 3 hrs. under the new conditions. These changes in size and synthetic activity occur much earlier than any measurable morphological alteration. The data give good evidence for the fact that the striking change in the morphogenesis is preceded by a fundamental change in the synthetic activity of the nucleus and nucleolus.
Die Beziehung zwischen Milchsäurekonzentration und Gewebs-pH beim DS-Carcinosarkom der Ratte
Authors: Rauen Hermann Matthias , Friedrich Michael , Norpoth Klaus 
Published: February 2015

Correlation of lactate-concentration and H⊕-concentration in tissue of rat DS-carcinosarcoma was tested with an improved method by intravital pH-measuring.
After i. v. dosages of glucose the testing was effected by measurement of 24 points equally distributed within the pH-range of about 6.1 — 7.1.
Therefrom we compute the acidification factor

In the tested pH-range the factor is practically constant.
Die Einwirkung von Strahlung auf Nucleinsäure-Bestandteile X
Authors: Fahr Egon , Gattner Hans , Dörhöfer Günther , Kleber Rolf , Popp Heinrich 
Published: February 2015

Der Zerfall der bei der UV-Bestrahlung von Uracil, Uridin, Uridin-2′ (3′) -phosphat, Uridin-5′-phosphat und Uridin-5′-triphosphat 3 entstehenden 6-Hydroxy-dihydrouracil-Derivate I in die entsprechenden Uracil-Verbindungen und Wasser wurde kinetisch bei verschiedenen Temperaturen und in verschiedenen Medien untersucht.
Die kinetischen Messungen zeigen, daß der Zerfall sehr ausgeprägt durch den am N-1-Atom befindlichen Ribose- bzw. Ribosephosphat-Rest beeinflußt wird. Die Ursache dieser Beeinflussung wird diskutiert.
In Übereinstimmung mit anderen von uns ausgeführten Untersuchungen 2c beweisen die Messungen, daß nicht ohne weiteres vom reaktiven Verhalten eines Pyrimidins selbst auf das des entsprechenden Nucleosids bzw. Nucleotids und damit auf das des Pyrimidin-Teils in der Nucleinsäure geschlossen werden kann.
Einfluß von Endoxan (Cyclophosphamid) und 6-Mercaptopurin auf den Nucleinsäure-Stoffwechsel der Rattenmilz während der Synthese von Antikörpern gegen Brucella abortus
Authors: Kröger H. , Papanastasiu D. , Potel J. 
Published: February 2015

1. Endoxan hemmt, insbesondere während der Erstimmunisierung, die Ausbildung von Antikörpern gegen Brucella abortus; 6-Mercaptopurin hat einen weitaus geringeren Effekt.
2. Beide Substanzen vermindern die DNS-Synthese in der Rattenmilz erheblich, die der RNS hingegen nur wenig.
3. Die Induktion der Tyrosin-α-Ketoglutarat-Transaminase in der Rattenleber wird durch Endoxan nicht gestört.
4. Diese Ergebnisse lassen den Schluß zu, daß bei der Erstimmunisierung zur Ausbildung der Antikörper eine DNS-Synthese unerläßlich ist.
Hemmung des cytopathischen Effektes durch Blockierung der DNS-Synthese von Vaccinia-Virus mit 5-Fluor-2'-desoxyuridin. Autoradiographische Untersuchungen
Authors: Henigst W. , Pielsticker K. 
Published: February 2015

5-Fluor-2′-desoxyuridin (FUdR) blockiert in tierischen Zellen und Bakterien fast ausschließlich die DNS-Synthese. Auch die Vermehrung von Viren, deren Genom aus DNS besteht, wird in derartigen Zellen selektiv gehemmt.
Wir versuchten mit der meist verwendeten FUdR-Dosis von 1 μMol/l den cytopathischen Effekt von Vaccinia-Virus in „KB“-Zellfilmen (monolayer) zu unterdrücken. Dies gelang jedoch erst mit 50 μΜοl/l FUdR. Zur Klärung der diskutierten möglichen Ursachen dieses Versagens untersuchten wir mit 3H-markiertem Thymidin (3H-TdR) die Vorgänge bei der Vaccinia-Virus-Infektion und bei deren Hemmung. Die autoradiographische Auswertung ergab folgendes:
Mit 1 μΜοl/l und mit 50 μΜοl/l behandelte Zellfilme wiesen weit mehr 3H-TdR-markierte Zellkerne auf als unbehandelte Kontrollen, was als Synchronisationseffekt von FUdR angesehen wird.
Die Unterdrückung der Zell-DNS-Synthese durch die Vaccinia-Virus-Infektion war deutlich zu beobachten, ebenso die Ausbildung der cytoplasmatischen Herde der Virus-DNS-Synthese.
Bei Verwendung von 1 μΜο/l FUdR wurde ein verzögertes Ingangkommen der Virus-DNS-Synthese beobachtet. Anzeichen hierfür blieben bei 50 μΜοl/l aus.
Über die relative Lage von Energietermen bei einigen photochemisch aktiven organischen Farbstoffen
Authors: Stanienda A. 
Published: February 2015

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.
Die kurzzeitigen ultravioletten Differenzspektren bei der Photosynthese
Authors: Stiehl H. H. , Witt H. T. 
Published: February 2015

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 hνII and oxidized by hνI
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).
Cytochrom-b-563 als natürlicher Elektronenüberträger in einem zyklischen Elektronentransport der Photosynthese
Authors: Weikard J. 
Published: February 2015

By excitation of spinach chloroplasts with flashes (5 · 10-5 sec) of far red light hvI (λ=728 nm) and with addition of 2·10-4M/I benzylviologen as electron acceptor irreversible absorption changes are observed as depicted in fig. 1 top. With 10-3 M/l K3Fe (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 K3Fe (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.
On the ion transport system of photosynthesis — Investigations on a molecular level —
Authors: Junge W. , Witt H. T. 
Published: February 2015

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 (&lt; 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.
Selektive Thermosensibilisierung von Ehrlich-Mäuse-Ascites-Krebszellen durch Diäthylstilboestrol
Authors: Ardenne M. Von , Reitnauer P. G. 
Published: February 2015

Die Information, daß verschiedene Sexualhormone bei Konzentrationen um 10-5g ml-1 die Atmung von EMAC-Zellen sehr stark hemmen, während bei Herz- und Leberzellen die Hemmung erst bei um zwei Zehnerpotenzen höheren Konzentrationen eintritt, veranlaßte uns dazu, die Eignung von Diäthylstilboestrol zur selektiven Thermosensibilisierung von Krebszellen zu untersuchen. Aus wiedergegebenen in-vitro-Messungen mit Ehrlich-Mäuse-Ascites-Carcinom-Zellen geht hervor, daß diese relativ ungiftige Substanz sich hervorragend zur selektiven Thermosensibilisierung von Krebszellen eignet. Die Sensibilisierungs-Wirkung bleibt auch unter nahezu anaeroben Bedingungen bestehen und setzt schon bei der relativ niedrigen Konzentration von 1 bis 3 · 10—6 g ml-1 ein. Die in-vitro-Beobachtung überadditiver Effekte beim Zusammenwirken schwacher Konzentrationen (Dosen) von Diäthylstilboestrol und Vitamin K3 bzw. analog wirkender Substanzen bei verschiedenen Temperaturen veranlaßt zur Formulierung des therapeutischen Prinzips steigender Gesamtwirkung durch Kombination vieler (etwa gleich starker) Angriffe mit abnehmender Einzeldosis auf das gleiche System.
Wie zuerst beim Vitamin K3 beobachtet, besteht auch beim Diäthylstilboestrol eine sehr starke Streuung der Sensibilisierungs-Wirkung zwischen verschiedenen Zellsuspensionen. Gegenwärtig wird versucht, diese Streuung durch gezielte weitere chemische Maßnahmen herabzusetzen. — Aus invitro-Messungen über den Einfluß der Hyperthermie-Temperatur ist zu erwarten, daß bei Steigerung der Körpertemperatur von 37 °C auf 41 °C die Wirkung der Hyperthermie durch Diäthylstilboestrol (evtl. + Vitamin K3) bzw. die Wirkung des Diäthylstilboestrols durch Hyperthermie (evtl. + Vitamin K3) vervielfacht wird. Die Wirkungszunahme ist gerade dann besonders stark, wenn die chemische Attacke allein nur schwache Effekte hat. Dies ist ein Ergebnis, das wahrscheinlich bald im klinischen Bereich ausgenutzt werden kann. — Nach Besprechung der toxikologischen Daten wird auf die in-vivo-Dosierung von Diäthylstilboestrol eingegangen. Aus Messungen an Kleintieren wird abgeschätzt, daß bei i.v.-Dauerinfusion (200 min) einer verträglichen Dosis in den Körpergeweben stationär Konzentrationen von Diäthylstilboestrol erhalten werden, die höher und z. T. sogar wesentlich höher liegen als die zur Thermosensibilisierung von EMAC-Zellen notwendige Konzentration. Die günstige Pharmakokinetik des Diäthylstilboestrols erklärt sich z. T. dadurch, daß diese Substanz im Organismus kaum abgebaut wird. In-vivo-Versuche mit Kleintieren bestätigten den selektiven Charakter der Thermosensibilisierung von Krebszellen mit Diäthylstilboestrol.
Regulation der UDPG-Pyrophosphorylase-Aktivität in Acetabularia
Authors: Zetsche Klaus 
Published: February 2015

The activity of UDPG-pyrophosphorylase [EC 2.7.7.9] was investigated during the morphogenesis (stalk and cap formation) of the unicellular and uninucleate green alga Acetabularia mediterranea. The activity of this enzyme is strongly related to the development of the cap. There was a substantial increase in the activity of the enzyme during cap formation. This increase in enzyme activity during cap formation also took place in anucleate cells. These findings are in good agreement with the fact that the glucose and galactose content of the cell wall of the cap is much higher than that of the stalk wall.
The increase in enzyme activity in nucleate and anucleate cells was reversibly stopped by puromycin and actidion. Therefore the increase in the pyrophosphorylase activity must be due to synthesis of this enzyme.
Actinomycin inhibits only the synthesis of the pyrophosphorylase in regenerating nucleate posterior parts of the cell. No inhibition occurs in anucleate cells with intact apical stalk because the cells contain a store of relatively stable messenger-RNA in the anterior parts of the stalk. On the other hand actinomycin inhibits the increase in chlorophyll content in both cell parts nucleate or anucleate.
These findings indicate that the synthesis of UDPG-pyrophosphorylase in Acetabularia does not involve a direct regulatory function of nuclear or extranuclear genes (as for example chloroplast genes). Therefore we have to conclude that the synthesis of this enzyme was regulated in the cytoplasm at the level of translation.
Untersuchungen zur Reaktion der Alkoholdehydrogenasen mit Tritium-markierten Substraten
Authors: Palm Dieter , Fiedler Tankred , Ruhrseitz Dorothea 
Published: February 2015

[1,1-T]-ethanol,:1,1-T]-propanol and [1,1-T]-butanol exhibit small isotope effects (kH/kT=1.3-1.8) in the liver alcohol dehydrogenase catalyzed reaction NAD® + alcohol ⇌aldehyde +NADH+H®. Presence of semicarbazide (with [1,1-T] -ethanol) or substrat inhibition (with [1,1-T] -butanol, 2.10-2-m.) raises the isotope effect (up to 4.1 at 25 °C) by introducing partial irreversibility to the interconversion step of the ternary complexes. This is in agreement with the Theorell-Chance mechanism as extended by DALZIEL. Thus, isotope effect determinations confirm both, the presence of ternary complexes and their kinetic insignificance for lower aliphatic substrates.
The results are markedly different from analogous kinetics with the yeast enzyme.
Über die strukturabhängige hämolytische Aktivität einiger Cholin-Phosphatide
Authors: Arnold D. , Weltzien H. U. 
Published: February 2015

Eine Anzahl synthetischer Cholinphosphatide wurde hinsichtlich ihrer hämolytischen Wirksamkeit untersucht. Die Lyse der Erythrocyten wurde dabei sowohl in ihrem zeitlichen Verlauf verfolgt, wie auch durch Endpunktsbestimmung bei verschiedenen Konzentrationen quantitativ erfaßt.
Ein direkter Zusammenhang zwischen der Grenzflächenaktivität und der hämolytischen Wirksamkeit der Substanzen besteht nicht. Innerhalb homologer Verbindungsreihen wird dagegen durch die Kettenlänge des apolaren Teils im Molekül eine scharfe Grenze zwischen lytischen und nicht-lytischen Verbindungen gezogen. So zeigt beispielsweise das sehr stark grenzflächenaktive Dipelargonoyl-α-lecithin gegenüber Humanerythrocyten keinerlei hämolytische Wirksamkeit, während Dicaprinoyl-α-lecithin bei gleicher Grenzflächenaktivität eine deutliche Hämolyse verursacht.
Bei einigen der untersuchten Phosphatide wurde überdies ein diskontinuierlicher, zweistufiger Verlauf der Zellzerstörung beobachtet.
Strahleninaktivierung von Ribonuclease bei erhöhten Temperaturen und unterschiedlichen Dosisraten
Authors: Kürzinger Klaus , Jung Horst 
Published: February 2015

The radiosensitivity of dry ribonuclease was determined at various temperatures between 120 °K and 440 °K using 2 MeV protons. Within this temperature range the inactivation cross section S (T) of ribonuclease may be described as a function of temperature by the expression S(T) = (1.28 + 16·e-1000/RT+14000·e-6500/7RT)·10-14 cm2 .
This result indicates that the observed radiation damage to ribonuclease is produced by three different mechanisms, one being independent of temperature, the other two having apparent activation energies of 1 kcal/mole and 6.5 kcal/mole, respectively. From these relatively small activation energies the conclusion may be drawn that radical reactions contribute to the inactivation of enzymes in the dry state. Experiments with Co gamma radiation showed that the radiosensitivity of ribonuclease at 77 °K depends on dose rate; at room temperature a dose rate effect was not observed.
On the X-Ray Inactivation at Various Temperatures of Trypsin in Dry State and Aqueous Solution
Authors: Oksmo Øyvind , Brustad Tor 
Published: February 2015

The X-ray sensitivity of trypsin has been studied both in dry state and in dilute solution (0.1 mg/ml) of 10-3 N HCl, as a function of the sample temperature during irradiation. Oxygen present during irradiation acts as a sensitizer when the exposure is carried out in frozen aqueous solution as well as in dry state, but it acts as a protector when the enzyme solution is exposed at room temperature. There is a considerable indirect effect when trypsin is exposed in frozen aqueous solution, above 200 °K, and even at 77 °K a small indirect effect is apparent.
When trypsin is exposed in 10-3 N HCl at room temperature about 85 per cent of the indirect effect is eliminated when the solution is saturated with O2 , (known as an effective scavenger for e ⊖
aq and H) and most of the remaining indirect effect is eliminated if the enzyme solution also contains 100 mM C2H3OH (known as an effective OH scavenger).