Showing papers in "Naturwissenschaften in 1987"

Auditory evoked potentials indicate the loss of neuronal oscillations during general anaesthesia

Abstract: Human 58.9 53.3 37.6 43.3 27.7 26.7 Dog 60.3 56.7 39.0 46.7 29.8 30.0 Kangaroo 57.4 60.0 41.1 56.7 27.0 30.0 Echidna 57.4 43.3 41.8 50.0 Platypus 55.3 50.0 41.1 56.7 29.8 30.0 Pheasant 54.6 50.0 Chicken 53.2 60.0 43.3 56.7 29.1 30.0 Turtle 55.3 60.0 . . . . Viper 48.9 53.3 Caiman 51.1 63.3 36.9 53.3 Newt 44.0 5 6 . 7 . . . . Carp 49.6 66.7 34.8 33.3 Shark 36.9 43.3 . . . . Lamprey 30.5 36.7 Mollusc 24.1 43.3 Broad bean . . . . 18.4 23.3

Pentachromatic visual system in a butterfly

Abstract: and mammals. The two segregated frequency ranges of best localization performance in the pigeon (250-500Hz and 2-4kHz) could reflect the operational ranges of two distinct binaural mechanisms as proposed by the classic duplex theory of directional hearing [15]: the perception of interaural time (phase) differences at low frequencies and of interaural intensity disparities at high frequencies. The transitional zone between these mechanisms could correspond to the range of poor localization capabilities at 1-2 kHz determined by both, the physiological high-frequency limit for phase locking in the auditory nervous system [16] and the physical low-frequency limit for interaural level differences due to the acoustic shadow of the head. Although this interpretation offers an explanation for the frequency dependence of auditory localization, it cannot, however, be completely excluded that the pigeon may use a pressure gradient system as suggested for the Japanese quail [17]. To solve this problem, measurements of the interaural intensity and phase difference thresholds are required. These behavioral experiments using heart-rate conditioning are in progress. First results are consistent with the hypothesis of combined binaural phase and intensity difference perception in sound localization.

Streß bei Pflanzen

Abstract: Du point de vue des botanistes, le stress peut etre decrit comme un etat dans lequel l'augmentation des demandes faites vis-a-vis du vegetal conduit a un debut de destabilisation des fonctions, suivi d'une normalisation et d'une amelioration de la resistance. Si les limites de la tolerance sont depassees et les capacites d'adaptation surchargees, des dommages permanents peuvent apparaitre allant jusqu'a la mort

Inheritance of olfactory response to sex pheromone components in Ostrinia nubilalis

Abstract: Fig. 3. Distribution of electrosensory organs in two sections of skin excised after 42 days (A) and 112 days (B, cluster of Fig. 2 B) following nerve deflection. Dimensions of the histologically examined sections of skin in mm the photographed area (Fig. 2A). It is unclear why a maximum of 90 out of an expected 350 organs were induced in the observed area and why the proportion of the three organ types in the newly induced population is different from the original innervated population (note only one mormyromast in Fig. 3 A). The spatial distribution of the newly induced organs of different types within a cluster appears random (Fig. 3). This indicates that every region in the observed sensory skin area is equally capable of differentiation into the receptor type which is coded by the organ-controlling substance specific to the regenerated nerve fiber. In Fig. 3 A, accumulation of ampullary and tuberous organs is found in the upper and lower half of the cluster, respectively. There is a tendency for tuberous organs to accumulate in the upper right and lower left of the skin section of Fig. 3 B. A reasonable explanation for this phenomenon may be that the afferent fibers belonging to one organ type are grouped within the nerve trunk.

Lethal fighting among dimorphic males of the ant, Cardiocondyla wroughtonii

Abstract: In most ant species, males are winged and disperse from their maternal nests on nuptial flights prior to mating [1]. However, in a small but diverse minority of ant genera, wingless and highly worker-like (ergatoid) males have evolved; and some species produce both winged and ergatoid males [2]. Little is known about the reproductive biology of many of these species, but if ergatoid males mate then they must do so in or near their maternal nest, a situation which could provoke intensive reproductive competition among males [3]. Ergatoid males of one ponerine ant species are known to fight one another, apparently in this context [3]. Colonies of the myrmicine ant, Cardiocondyla wroughtonii (Forel), frequently have multiple queens (polygyny) and produce both winged and ergatoid males [4, 5]. Our observations reveal that the ergatoid males are morphologically and behaviorally highly specialized for fighting, and regularly engage in lethal combat with one another so that there is typically only a single ergatoid male per nest. In contrast, winged males never appear to fight, and often coexist in large numbers with a resident ergatoid male. In the laboratory, both types of males mate within their nests with the young winged (alate) queens

A universal constant in temporal segmentation of human short-term behavior

Abstract: Human time perception is characterized by an integrative mechanism [1] that relates successive mental events in such a way that a perceptual pattern is formed as in a melody or a verbal utterance. The temporal limit of this integrative mechanism has been found to be of the order of 3 s [2]. A necessary consequence o f sequential integrations of events with the same time constant is a quasi-periodical structure of perception and, possibly, mental activity in general [2, 3]. We have obtained evidence now that not only perception but also overt behavior is characterized by a similar time constant [4]. Human behavior appears to be organized in such a way that short-term movement episodes with an obvious segmentation are embedded within 3-s temporal windows. Thus, both perception and action appear to be controlled by a universal temporal principle. The behavioral data analyzed were taken from four different cultures, i.e., Europeans, Trobriand Islanders, Yanomami Indians, and Kalahari Bushmen. The scenes filmed were unstaged

Sex and parental experience determine the onset of an instinctive behavior in mice

Abstract: Ultrasonic calls of young mouse pups (Mus musculus) release parental care (retrieving pups, licking, nest-building) in adults of either sex [1]. Here, we demonstrate that female and male mice need different periods of contact with pups both for the performance of pup retrieving and for the acquisition of the preference for its ultrasonic releaser. The results show a sex-dependent difference in the occurrence of an instinctive behavior and in the speed of learning to associate a stimulus with this behavior. Behavioral tests were conducted with 2-5-month-old Mus musculus (outbred strain N M R I ) including mothers and fathers with caretaking experience for one total broodcaring period (24 days), fathers and females co-caring for a litter over 1-5 days postpartum of the mother and males and females without any breeding experience and without pup contact (naive animals). The same setup and procedures as described elsewhere [2] were used. In short, experimental animals were adapted at least for 5 h before tests started to a soundproof room and a running board (length 110 cm, width 8 cm) with a central nest depression. Experienced mothers and fathers had their whole second litter, co-caring fathers and females at least seven pups in the nest depression. Tests were conducted in dim red ( ~ 1 lx) illumination either between 0700 and 1100 hours or 1700 and 2100 hours. Experimental animals had to retrieve five pups o f their own (mothers and fathers) or of a donorlitter (2-5 days old) which were thoroughly embrocated with the nest material of the animal in test. Pups were placed 30 cm from the nest depression on either side of the running board. I f the first pup was not retrieved within 10 min, animals were scored unresponsive. Table 1 shows the results of the retrieving tests. Naive males and fathers cocaring for their pups for only one day are clearly non-retrieving. More than half of the naive females and a significant portion (p < 0.05) of the females co-caring for one day retrieve. Animals of either sex with pup experience for five days or more all show retrieving behavior (p < 0.01). Pup-retrieving behavior thus can occur in totally unexperienced females and becomes fully established after one day of sensitization with pups. Males (fathers) need more than one day sensitization with pups to develop this behavior at all.

New structural aspects of the Dufour's and venom glands in social insects

Abstract: only, and because the swelling and dissolution processes are very complex, the effects observed cannot completely be attributed to the local water structure. The expression \"water structure\", thus, stands for the state of order estimated by the described method just as the definition of a liquid structure always depends upon the experimental conditions. The change of the water structure in the presence of 1% bentonite is equal to a variation of the osmotic pressure by 7.5 mOsmol. With respect to the fact that in a cell 1 mOsmol may cause an internal pressure of 2.27 kPa [9], this value refers to the relatively high importance which even a small change of the water structure at interfaces implies for biological and other disperse systems. The effect can be increased depending upon the composition of the system. The results confirm the deviation of the \"water structure\" in suspensions and, on the other hand, the suitability of the new indirect method for structure estimations. Of course, the accuracy of the method is influenced by the quality of the microcapsules.

The chemical composition of the dust of comet P/Halley as measured by ``PUMA'' on board VEGA-1

Abstract: Analyse de la composition chimique, de la distribution de masse et de densite des particules de poussiere de la comete Halley par un spectrometre de masse a bord de la sonde spatiale Vega-1

Identification of 5,9-dimethylheptadecane as a sex pheromone of the moth Leucoptera scitella.

Abstract: changes occurred in an additional eight positions resulting in an overall homology of 87%. Similar evolutionary processes can be deduced from the tRNA)~N sequence. The Locusta gene of 70 nucleotides is 3 bp longer due to two base insertions in the T~PC and a third in the V loop. An additional seven base exchanges result in an overall homology of 86%. The tRNA~j%N sequence reveals an AA mismatch at the beginning of the anticodon stem (see arrow). An AA mismatch in the same position is reported for a t R N A Val gene in Neurospora [11]. Examples for mismatches in the T ~ C stem are a TT mismatch in the phe tRNAvv c gene of Tetrahymena [1] and in a t R N A Val gene from A. albopictus [5]. A copy of the leu tRNAcv N gene indicated in Fig. 1 A is found within a cloned D N A fragment of nuclear D N A homologous to mitochondrial genes [6, 12, 13] and is thus part of a \"promiscuous, D N A \" sequence.

Palynology in metamorphic rocks: Indication of early land plants

Abstract: H.D. Pflug and E. Reitz Geologisch-Palfiontologisches Institut der Universit/it, D-6300 Giel3en enough, because the mineral matrix disturbs the observation. It is, therefore, neccessary to isolate the spores from the rock by a special maceration which dissolves the mineral matter but leaves the spores intact. The following findings are results of our studies. Trilete spores of early land plants have been detected in a garnet-bearing mi-

The steering of zigzagging flight by male gypsy moths

Abstract: thesis [11]. The melatonin synthesis is not only affected in the pineal but also in the retina itself. Comparable influences of magnetic fields on enzyme activities in the pituitary gland are not known. Therefore, a discussion on the mode of action of the disturbed MF on pigment movement within the melanophores during background adaptation remains rather speculative. In contrast to tail melanophores those in the head region have been reported not to react to local illumination [12], i.e., do not show a \"pr imary response\". The observation that the responses o f the two \" types\" of melanophores in X. laevis tadpoles to incident light and to conditions of a disturbed MF are very different favors a working hypothesis that includes hormonal as well as direct photic mechanisms. Received January 14, 1987

Effects of 2,6-DCB on plasma membrane rosettes of wheat root cells

Abstract: mice is strongly influenced by the odors experienced during the first two weeks of life. An impoverished odor environment drastically reduces the number of spontaneously active bulbar neurons; the addition of one single monomolecular odorant increases this number significantly. The neural response to this exposure odor was enhanced as well, although these mice had no contact with this substance for about two months. These differences are independent of the odor spectrum smelled in later life. It can be concluded that the neural specificity in the olfactory bulb to given odors is established in the first few weeks and remains manifested in the adult mouse.

50 Jahre Phalloidin

Abstract: Phalloidin, like the later-detected phallotoxins, consists of a cyclic heptapeptide backbone, the ring being crosslinked by a 2'-indolylthioether moiety (tryptathionine). After intraperitoneal administration--not per os--it will, after a short time, damage the liver specifically, presumably in consequence of its very tight binding to F-actin preventing its dissociation. This affinity can be utilized for a sensitive visual identification of F-actin by using fluorescent derivatives.

Die pflanzliche Vakuole als Speicher

Abstract: Plant cell vacuoles not only maintain cellular turgidity, but are known as a deposit for both lytic enzymes and end products noxious for the cytoplasm. In addition, vacuoles accumulate nutritive solutes and function as a storage pool for proteins, sugars, organic acids etc. Long-term as well as diurnal storage and release processes emphasize the role of the central vacuole in metabolic regulation in a plant cell. D ie groBe, dem Mikroskopiker wohlvertraute Zentralvakuole der Pflanzenzelle ist als Teil des funktionell hochdifferenzierten Endomembransystems eine vergleichsweise volumin6se Komponente, die sich im Laufe der Zelldifferenzierung erst als Folge eines st/indigen Membranflusses aus dem ER-System fiber den Golgi-Apparat herausbildet. Sowohl der Innenraum der Vakuole als auch die vom Endomembransystem insgesamt umschlossenen Rfiume, ferner die Kernhfille, die R/iume zwischen innerer und /iuBerer Mitochondrienund Chloroplastenmembran sowie endlich das Thylakoidkompartiment werden der Matrixphase als sog. Vakuom gegeniibergestellt. Matrixphase und Vakuom sind gegeneinander durch Membranen lfickenlos abgegrenzt. Physikalische und chemische Eigenschaften der Membranen entscheiden fiber den notwendigen st/indigen Transfer von Stoffen und Signalen, und zwar in /iuBerst unterschiedlicher Weise, wie das etwa ffir die /iuBere und die innere Chloroplastenmembran oder die Thylakoide gut bekannt ist [1].

Pestizid-Rückstände in Nahrungspflanzen

Abstract: Die erst in den letzten Jahren charakterisierte Bildung loslicher und unloslicher pflanzlicher Konjugate von Pestiziden kann als eine Art der Persistenz und Ruckstandsbildung gesehen werden. Die wenigen vorliegenden Untersuchungen lassen eine teilweise Bioverfugbarkeit und im Einzelfall die Moglichkeit toxikologischer Risiken, z.B. Mutagenitat, vermuten. Neben den bei der Zulassung von Pflanzenschutzmitteln hauptsachlich betrachteten Wirkstoffresten im Erntegut sollte daher verstarkt die tatsachliche Fremdstoffbelastung im Magen-Darm-Trakt von Tier und Mensch untersucht werden.

A distinct ultrasound-processing area in the auditory cortex of the mouse

Abstract: (control data published in [7]), we obtain a non-significant compass vector in a very different direction (c~N= 85 ~ r~ = 0.16), indicating that the inexperienced birds from our loft, like the experienced birds [8], have no \"preferred compass direction\". An extensive study with trained birds had revealed only very little effect o f olfactory deprivation in Frankfurt pigeons [6]; the data of untrained birds presented here do not support Papi's and Watlraff's model [t, 2] either. This is important, because in discussions, it has been frequently assumed that the differences between the findings in Italy [1] and Wiirzburg [3] and the former Frankfurt findings [6] have been caused by the Frankfurt pigeons being more experienced than most birds in the other studies, who had no or only very little training. Yet our present data show that our untrained pigeons are also unaffected. The degree of experience alone does not seem to be the reason for the different results. An analysis of the development of orientation showed that the navigational system undergoes a fundamental change as young pigeons become more experienced [7]. Very young birds as in the present study rely on magnetic information obtained during the outward journey; their use of directional information collected en route is indicated by the well concentrated, homedirected orientation. This first strategy is obviously not affected by olfactory manipulation. Older, experienced pigeons that have established a \"naVigational m a p \" give up that strategy and mostly use local information; here we likewise found olfaction played only a minor role [6]. It seems that olfactory information is never an important factor for our Frankfurt pigeons. In this respect they apparently differ from the pigeons in some other lofts. It will be interesting to find out why.

First European record of a queen ant carrying a mealybug during her mating flight

Abstract: B 1 127

Callose-Synthese: regulation durch induzierten Ca2+-Einstrom in Pflanzenzellen

Abstract: Callose is a 1,3-fl-glucan which can be rapidly deposited at localized positions onto plant cell walls in order to reinforce and seal cells and tissues after mechanical injury, and during defense reactions against pathogens. In suspension-cultured cells callose formation can be induced by addition of polycations or certain amphipathic substances, which all appear to act by perturbation of the plasma membrane permeability, resulting in considerable K + leakage out of, and an increased C a 2+ uptake into the cells. It is suggested that this might lead to an increase in the concentration of cytoplasmic free Ca 2+ which directly and perhaps together with other less well-known effectors triggers the plasma membrane-located 1,3-fl-glucan synthase. This enzyme is strictly dependent on Ca 2+ in the g M range and can be further activated by polyamines. The suggested chain of events possibly has implications also in regard to some other physiological processes. C allose ist ein Polysaccharid der pflanzlichen Zellwand, das haupts/ichlich aus unverzweigten Ketten von 1,3-fi-verknfipften Glucose-Einheiten besteht. Mit gezielten F/irbetechniken kann es leicht sichtbar gemacht werden (Fig. 1). Aus diesem Grund wurden in den vergangenen hundert Jahren st/indig neue Beispiele fiir die Funktion von Callose bei Umbau und Reparatur der Zellw/inde von h6heren Pflanzen bekannt [i]. Beispiele aus dem Verlauf der normalen pflanzlichen Entwicklung sind die Pollenreifung [2] oder der Verschlul3 des wachsenden Pollenschlauchs hinter dem Protoplasten [3]. Letzterer h/ilt sich stets in der Pollenschlauchspitze auf, die auf die weir entfernte Eianlage zuw/ichst. Der verlassene Teil des Pollenkorns und -schlauchs wird in regelm/iBigen Abst/inden dutch callosereiche ,,Pfropfen\" abgetrennt, wodurch die Bildung von extrem langen Riesenzellen vermieden wird. St6rungen im komplizierten Wachstum des Pollenschlauchs durch das Narbenund Griffelgewebe und damit einherlaufende Callose-Ablagerungen sind auch an

Cytostatische Nicht-Platinmetall-Komplexe: neue Perspektiven für die Krebsbehandlung?

Abstract: Fur eine Reihe verschiedenartiger, anorganischer und metallorganischer Nicht-Platinmetall-Verbindungen wurden in den letzten Jahren zum Teil ausgepragte tumorhemmende Eigenschaften nachgewiesen. Damit hat sich den bereits klinisch bewahrten Platinmetall-Komplexen eine neue, chemisch heterogene Gruppe tumorhemmender Verbindungen zugesellt, die durch folgende biologische Eigenschaften gekennzeichnet sind: • Das Wirkungsspektrum der meisten Nicht-Platinmetall-Verbindungen gegenuber experimentellen tierischen und menschlichen Tumoren ist nicht identisch mit dem von Cisplatin. Dementsprechend durfte auch das klinische Aktivitatsspektrum unterschiedlich sein. Fur einige Gallium- und Germanium-Verbindungen konnte dies in klinischen Studien bereits belegt werden. • Die organschadigenden Eigenschaften der meisten tumorhemmenden Nicht-Platinmetall-Verbindungen, insbesondere derer, die weniger schwere Metallatome wie Titan oder Eisen enthalten, weichen grundlegend von dem fur Cisplatin bekannten Toxizitatsmuster ab. Theoretisch durfte es daher • Tumorhemmende Nicht-Platinmetall-Verbindungen verhalten sich somit in biologischer Hinsicht nicht analog den cytostatischen Platin-Komplexen und sind daher als eigenstandige Gruppen cytostatisch wirksamer Substanzen anzusehen und abzugrenzen.

Mikroanalytik in der pflanzlichen Biochemie

Abstract: Even between adjacent cells profound biochemical differences can exist. In order to resolve these differences, methods have been developed for analyzing small amounts of tissue. By a combination of microdissection of freeze-dried tissue and quantitative histochemistry even single cells can be biochemically characterized. We illustrate the power of this analytical system by comparing activities of some enzymes in different types of cells from a Vicia leaf. In addition, an assay is described, which allows the determination of photosynthetic oxygen evolution from single cells. p flanzliche wie tierische Gewebe sind aus einzelnen Zellen aufgebaut, die sich, auch wenn sie eng benachbart sind, in ihren biochemischen Eigenschaften grundlegend unterscheiden k6nnen. In einem Laubblatt grenzen z.B. Zellen, die den Gasaustausch regulieren (Stomata), unmittelbar an andere, die entweder das Blatt nach auBen lain abgrenzen (Epidermis) oder Photosynthese betreiben (Mesophyll). Schon aufgrund ihrer unterschiedlichen Funktion sind deshalb ganz spezifische biochemische Eigenschaften zu erwarten. Die Entwicklung von Methoden zur Gewinnung und Analyse kleinster Probenmengen war und ist eine Herausforderung an den Biologen. In diesem Beitrag sollen zwei Beispiele ffir Mikroanalytik herausgegriffen werden, die noch wenig verbreitet sind, deren Anwendung aber v611ig neue Aussagen zur Funktion einzelner Zellen und zur Arbeitsteilung in Geweben erm6glicht.

Induction of storage protein synthesis in embryos of mature plant seeds

Abstract: Maturing seeds of higher plants accumulate large amounts of storage proteins which are broken down after germination to serve the nutritional needs of the developing seedling with respect to amino nitrogen [1]. Seed storage proteins also provide the basic nitrogen source in the diet of man and animals. The developmental control of expression of storage protein genes during the life cycle of a plant is therefore of great interest. So far, mass synthesis of storage proteins, usually comprising about 30% of the dry matter of a mature seed, has been found to be strictly confined to the period of seed maturation [21. During the remainder of the plant's life, the storage protein genes appear to be firmly repressed by an unknown mechanism. It is generally assumed [3-5] that desiccation of the mature seed irreversibly terminates the maturation period and reorients the developmental program, after a state of metabolic quiescence, towards expression of those genes which are directing germination and seedling growth. This stable switching from a maturation to a germination program in embryo development is highlighted by the recent finding that storage protein genes of Phaseolus transferred to the genome of Nicotiana via Agrobacterium plasmids are expressed in the receiver plant only during seed maturation [6]. Here we report that embryos isolated from mature, dry seeds of mustard (Sinapis alba L.) are able to resume the synthesis of storage protein if conditions are met which permit undisturbed maturation development in the immature embryo. In mustard seeds, about 80% of the storage protein is represented by a protein complex with a sedimentation coefficient of 13 S. It is composed of six major polypeptides of 16.5, 18.5, 19.5, 26, 28.5, 34 kDa molecular weight. In addition, precursors of 51 and 56 kDa, giving rise to four of these polypeptides (16.5, 28.5, 19.5, 34 kDa) can be identified in maturing embryos in the period of active storage protein synthesis

Occurrence of rosettes in the ER membrane of young Funaria hygrometrica protonemata

Abstract: Characteristically aggregated particles, forming \"roset tes\" with a diameter of 24 mn and consisting o f 6 subunits, have been detected in the PF of freezefractured plasma membranes in a varity of cellulose-forming cells, from algae to higher plants [1-6, 8]. The strong correlation between the occurrence and distribution of the rosettes and the position and quantity of cellulose production supports the hypothesis that the rosettes play an important role in the cellulose synthetase complex [2, 4, 6, 7]. Studies on the development of these structures have revealed their occurrence in membranes o f Golgi vesicles and Golgi cisternae [2, 9]. This indicates that the rosettes are transported to and incorporated into the plasma membrane via Golgi vesicles. It is, however, as yet unknown, whether they are formed in the dictyosomes or earlier, i.e., in the endoplasmatic reticulum (ER). To investigate the origin of the rosettes, young protonemata o f the moss Funaria hygrometrica Sibth. were freezefractured. Freshly germinated spores with only one filament were cultivated and processed as previously described [7J. Although many dictyosomes in different ceils have been inspected, only few rosettes have been found. They appeared in the peripheral dictyosome membrane, in Golgi vesicles (in one case two rosettes could be seen in the PF of a vesicle) and it was possible to detect them in cisternae o f the ER (Fig. 1). These observations suggest that the rosettes aggregate within the ER and then pass the Golgi apparatus, obviously being restricted to the rims of cisternae and peripheral vesicles. Alternatively it cannot be completely excluded that the rosettes aggregate within the plasma membrane and that those found in the internal cytomembranes represent recycling rosettes. This explanation would be consistent with the fact that in spite of an obviously high turnover rate [6, 7] the number of rosettes observed in cytomembranes is relatively low. On the other hand, the observations in Micrasterias that during secondary Received June 29, 1987

The insecticide Azadirachtin reduces predominantly cellular RNA in Tetrhymena

Abstract: preparative gas chromatography even on optically impure chiral stationary phases, the enantiomer eluting as the second fraction may be contaminated with the preceding eluent still present in the post-column flow system. The second eluting enantiomer may be reverted to the first fraction by using the stationary phase of opposite chirality. It is beneficial in this respect that carvone as the chiral recognition principle in 2 is commercially available in both antipodal forms with high enantiomeric purity from natural sources. According to Figs. 2 and 3, the parent compound 1 a as well as the three enantiomeric pairs of the 2.7-dimethyl-l.6dioxaspiro[4.4]nonanes l d, l e and i f are also quantitatively separated employing the same column. The small "p la teau" which appears between the enantiomeric fractions o f l a is not due to incomplete enantiomer separation but is caused by the inherent configurational lability (leading to enantiomerization) of spiroketals [7]. Fortunately, the semi-preparative enantiomer separation of 1 can be performed at low temperature (45 ~ where enantiomerization is minimized.