Lindera Glauca Research Articles

Population genetic structure and variability in Lindera glauca (Lauraceae) indicates low levels of genetic diversity and skewed sex ratios in natural populations in mainland China.

Lindera glauca (Lauraceae) is a tree of economic and ecological significance that reproduces sexually and asexually via apomictic seeds. It is widely distributed in the low-altitude montane forests of East Asia. Despite the potential implications of a mixed reproductive system in terms of genetic diversity, few studies have focused on this aspect. In this study, the genetic structure of wild populations of L. glauca was investigated via genetic analyses. Overall, 13 nuclear microsatellites (nSSRs) and five chloroplast microsatellites (cpSSRs) were used to genotype 300 individual plants, taken from 20 wild populations (a small sample size in some wild populations is due to the limitation of its specific reproduction, leading to certain limitations in the results of this study) and two cultivated populations ranging across nearly the entire natural distribution of mainland China. The populations exhibited low levels of genetic diversity (nSSR: AR = 1.75, Ho = 0.32, He = 0.36; cpSSR: Nb = 2.01, Hrs = 0.40), and no significant effect of isolation by distance between populations existed, regardless of marker type (nSSR: R2 = 0.0401, P = 0.068; cpSSR: R2 = 0.033, P = 0.091). Haplotype networks showed complex relationships among populations, and the H12 haplotype was predominant in most populations. Analyses of molecular variance obtained with nuclear markers (Fsc = 0.293, FST = 0.362) and chloroplast markers (Fsc = 0.299, FST = 0.312) were similar. The migration ratio of pollen flow versus seed flow in this study was negative (r = −1.149). Results suggest that weak barriers of dispersal between populations and/or the similarity of founders shared between neighbors and distant populations are indicative of the gene flow between populations more likely involving seeds. Wild L. glauca in mainland China was inferred to have highly skewed sex ratios with predominant females. In addition, some populations experienced a recent bottleneck effect, especially in Gujianshan, Chongqing, and southwest China (population GJS). It is suggested that few wild male individuals should be conserved in order to maintain overall genetic diversity in the wild populations of this species. These findings provide important information for the sustainable utilization and preservation of the overall genetic diversity of L. glauca.

Pseudoguaianelactones A–C: three unusual sesquiterpenoids fromLindera glaucawith anti-inflammatory activities by inhibiting the LPS-induced expression of iNOS and COX-2

The pseudoguaianelactones A (1) and B (2), two novel sesquiterpene lactones with an unprecedented [5,7,7] ring system featuring an α-methylene-γ-lactone moiety, together with a new pseudoguaianelactone C (3) were isolated from the roots of Lindera glauca. Pseudoguaianelactones A-C (1-3) inhibited nitric oxide (NO) production, with IC50 values ranging from 1.38 to 4.00 μM. Moreover, all compounds significantly suppressed the production of pro-inflammatory mediators (TNF-α, IL-6, IL-1β and PGE2) and the protein expression of the enzymes iNOS and COX-2.

Effects of fire and nitrogen addition on photosynthesis and growth of three dominant understory plant species in a temperate forest

Fire and atmospheric nitrogen (N) deposition have the potential to influence growth and productivity of forest canopy. However, their impacts on photosynthesis and growth traits of understory plants in forests remain largely unexplored. This study was conducted to examine the effects of burning and N addition on foliar N content, net photosynthesis and growth traits of three dominant shrub species (Vitex negundo, Lindera glauca and Symplocos chinensis) in a temperate forest in Central China. The experiment used a pair-nested design, with four treatments (control, burning, N addition and burning plus N addition) and five replicates. Leaf mass area (LMA), area-based concentrations of foliar N and chlorophyll (Nₐᵣₑₐ and Chlₐᵣₑₐ), net photosynthesis (Aₙ), stomatal conductance (gₛ), maximum photosynthetic rate (Aₘₐₓ) and maximal carboxylation rate (Vcₘₐₓ), basal diameter, height and branch length (BL) of the three species were measured. Across the three species, burning stimulated LMA, Nₐᵣₑₐ, Chlₐᵣₑₐ, Aₙ, gₛ, Aₘₐₓ and Vcₘₐₓ, and consequently enhanced basal diameter, height and BL. Nitrogen addition increased Aₙ and gₛ but did not affect LMA, Nₐᵣₑₐ, Chlₐᵣₑₐ, Aₘₐₓ, Vcₘₐₓ, basal diameter, height or BL. However, N addition strengthened the positive effects of burning on gₛ, Vcₘₐₓ, Aₙ and BL. The findings indicate the primary role of light resources in determining plant photosynthesis and growth of understory shrub species after fire and highlight that understory plants should be considered in projection of biomass accumulation and productivity of forests under environmental perturbations.

Construction of the chloroplast genome of Litsea coreana var. sinensis and phylogeny of Lauraceae

Litsea coreana var. lanuginose is an evergreen shrub or small tree of the genus Lauraceae. The complete chloroplast genome of L. coreana var. sinensis is 152,834 bp in length, containing an LSC region of 93,789 bp, an SSC region of 18,913 bp, and a pair of inverted repeats (IRA and IRB) of 20,066 bp each. The genome encodes of 127 genes, including 81 protein-coding genes, 8 ribosomal RNA genes, 36 transfer RNA genes, and 2 pseudogenes. Most of these genes occurred in a single copy, whereas 13 genes occurred in double copies, including all rRNA, 6 tRNA, and 3 protein-coding genes. The overall GC content is 39.1%. Phylogenetic analysis of cp genomes from 29 species of Lauraceae showed that cp genomes of L. coreana var. sinensis is most related to those of L. glutinosa, Laurus nobilis, and Lindera glauca.

Biodiesel from Lindera glauca oil, a potential non-food feedstock in Southern China

In this study, fruit oil of Lindera glauca was investigated for the first time as a promising non–conventional feedstock to produce biodiesel, which was performed using a two–step catalyzed process on a laboratory scale. L. glauca fruit has high oil content (43.35 ± 3.24%), and its oil has low acid value (2.18 mg KOH g−1). The fatty acid composition of LG oil mainly includes oleic acid (36.34% ± 1.1%), linoleic acid (10.53% ± 0.4%), palmitic acid (17. 30% ± 0.7%) and decanoic acid (15. 80% ± 0.5%). Four important factors for reaction conditions were repeatedly tested to obtained the optimum conditions, i.e., molar ratio of 10:1 (methanol/oil), sodium hydroxide (NaOH) concentration (1.50% w/w), reaction temperature (60 °C), and the reaction times (60 min), with a mean of 95.6% of biodiesel production. The main properties of LG biodiesel were conformed to EN 14214–08, ASTM D6751–10 and GB/T 20828–2014 standards, especially the oxidative stability (16.8 h) and Flash point (158 °C) were excellent. These results obtained in this work can provide important information for developing this non-food feedstock.

A new cerebroside from the twigs of Lindera glauca (Sieb. et Zucc.) Blume

Lindera glauca (Sieb. et Zucc.) Blume (Lauraceae) has been used to treat rheumatic arthritis, stroke, and cardiac pain. Phytochemical investigation of twigs of L. glauca (Sieb. et Zucc.) Blume resulted in the isolation and identification of a new cerebroside, glaucerebroside (1). The structure of 1 was elucidated by a combination of extensive spectroscopic analyses, including extensive 2D NMR, HR-MS, chemical reactions, and LC/MS analysis. Compound 1 is a relatively rare cerebroside with l-threo-configuration of the sphingosine part. This is the second example of identification of a cerebroside from the family Lauraceae. Compound 1 significantly inhibited nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated BV-2 cells, with an IC50 value of 23.84μM without inducing cell toxicity. This study suggests that glaucerebroside (1) can be an excellent candidate for development of novel anti-neuroinflammatory agents.

Integrated analysis of 454 and Illumina transcriptomic sequencing characterizes carbon flux and energy source for fatty acid synthesis in developing Lindera glauca fruits for woody biodiesel

BackgroundLindera glauca fruit with high quality and quantity of oil has emerged as a novel potential source of biodiesel in China, but the molecular regulatory mechanism of carbon flux and energy source for oil biosynthesis in developing fruits is still unknown. To better develop fruit oils of L. glauca as woody biodiesel, a combination of two different sequencing platforms (454 and Illumina) and qRT-PCR analysis was used to define a minimal reference transcriptome of developing L. glauca fruits, and to construct carbon and energy metabolic model for regulation of carbon partitioning and energy supply for FA biosynthesis and oil accumulation.ResultsWe first analyzed the dynamic patterns of growth tendency, oil content, FA compositions, biodiesel properties, and the contents of ATP and pyridine nucleotide of L. glauca fruits from seven different developing stages. Comprehensive characterization of transcriptome of the developing L. glauca fruit was performed using a combination of two different next-generation sequencing platforms, of which three representative fruit samples (50, 125, and 150 DAF) and one mixed sample from seven developing stages were selected for Illumina and 454 sequencing, respectively. The unigenes separately obtained from long and short reads (201, and 259, respectively, in total) were reconciled using TGICL software, resulting in a total of 60,031 unigenes (mean length = 1061.95 bp) to describe a transcriptome for developing L. glauca fruits. Notably, 198 genes were annotated for photosynthesis, sucrose cleavage, carbon allocation, metabolite transport, acetyl-CoA formation, oil synthesis, and energy metabolism, among which some specific transporters, transcription factors, and enzymes were identified to be implicated in carbon partitioning and energy source for oil synthesis by an integrated analysis of transcriptomic sequencing and qRT-PCR. Importantly, the carbon and energy metabolic model was well established for oil biosynthesis of developing L. glauca fruits, which could help to reveal the molecular regulatory mechanism of the increased oil production in developing fruits.ConclusionsThis study presents for the first time the application of an integrated two different sequencing analyses (Illumina and 454) and qRT-PCR detection to define a minimal reference transcriptome for developing L. glauca fruits, and to elucidate the molecular regulatory mechanism of carbon flux control and energy provision for oil synthesis. Our results will provide a valuable resource for future fundamental and applied research on the woody biodiesel plants.

Development and characterization of microsatellite loci for Lindera glauca (Lauraceae)

Premise of the study:Microsatellite primers were developed to investigate population genetic structure in Lindera glauca (Lauraceae).Methods and Results:Twenty-five microsatellite primers were developed and optimized for L. glauca using Illumina’s Solexa sequencing technology. These novel primers were found to be polymorphic in nine wild L. glauca populations with 81 total alleles confirmed and genotyped via capillary gel electrophoresis. The total number of alleles, observed heterozygosity, and expected heterozygosity for each population ranged from one to four, from 0.00 to 0.90, and from 0.00 to 0.79, respectively. In addition, the 25 primers were tested in 10 additional individuals of the related species L. communis, and all but four markers showed good amplification results.Conclusions:This set of microsatellite primers is the first specifically developed for L. glauca and will facilitate studies of genetic diversity and evolution among populations of this species.

A new rearranged eudesmane sesquiterpene and bioactive sesquiterpenes from the twigs of Lindera glauca (Sieb. et Zucc.) Blume.

A new rearranged eudesmane sesquiterpene, named eudeglaucone (1), and five known sesquiterpenes including (+)-faurinone (2) and four eudesmane-type sesquiterpenes (3-6), were isolated from the twigs of Lindera glauca (Sieb. et Zucc.) Blume. The structure of 1 was elucidated by a combination of extensive spectroscopic analyses, including extensive 2D NMR (1H-1H COSY, HMQC, HMBC, and NOESY) and HR-MS. Compound 1 was a relatively rare rearranged eudesmane sesquiterpene in terpenoids. All isolates were evaluated for their antiproliferative activities against four human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT-15). Compounds 3 and 6 showed significant cytotoxicity against SK-MEL-2 and HCT-15 cell lines with IC50 values ranging from 9.98 to 12.20μM. We also investigated the anti-neuroinflammatory activities of the isolates (1-6) in the lipopolysaccharide (LPS)-stimulated murine microglia BV-2 cell line by measuring nitric oxide (NO) levels. All isolates significantly inhibited NO production with IC50 values of 3.67-26.48μM without inducing cell toxicity.

De novo assembly and characterization of the floral transcriptome of an economically important tree species, Lindera glauca (Lauraceae), including the development of EST-SSR markers for population genetics.

Lindera glauca (Lauraceae) is an economically important East Asian forest tree characterized by a dioecy in China and apomixis in Japan. However, patterns of population genetic diversity and structure of this species remain unknown for this species due to a lack of efficient molecular markers. In this study, we employed Illumina sequencing to analyze the transcriptomes of the female and male flower buds of L. glauca. We retrieved 59,753 and 75,075 unigenes for the female and male buds, respectively. Based on sequence similarity, 44,379 (74.27%) unigenes for the female and 45,414 (60.49%) unigenes for the male were matched to public databases. We identified 11,127 putative differentially expressed genes between the female and male buds and 20,048 expressed sequence tag-simple sequence repeats (EST-SSRs). From 3147 primer pairs designed successfully, 120 were selected for validation of polymorphism, and 13 could reliably amplify polymorphic bands and exhibited moderate levels of genetic diversity (e.g., N A=4.42; H E=0.56) when surveyed across 96 individuals of altogether six L. glauca populations from China and Japan. One of the three population genetic clusters identified in China was fixed in Japan, suggesting a historical population bottleneck following island immigration. The present study has generated a wealth of transcriptome data for future functional genomic research focused on the variable reproductive system of L. glauca (dioecy, apomixis) as well as EST-SSR markers for population genetics studies and its intriguing evolutionary shift from dioecy to apomixis in the wake of island colonization.

Volatile Constituents from the Fruits of Lindera glauca (Sieb. et Zucc.) with Different Maturities

The volatiles of Lindera glauca (Sieb. et Zucc.) fruits with different maturities, grown in Jigongshan mountain, Henan China, were isolated by hydro-distillation method and analyzed by GC-qMS. Eighty seven constituents were identified in the essential oil from the middle July samples, comprising 73.94 % of the volatiles, and the major components were sesquiterpene hydrocarbons (40.02%) and monoterpene hydrocarbons (30.61%), of which β-ocimene (12.99%) is the major one, followed by α-pinene (4.07%) and β-caryophyllene (3.73%). In the oil from the middle August samples, the major components of the identified 72 components, comprising 88.64% of the essential oil, were monoterpene hydrocarbons (57.75%) and sesquiterpene hydrocarbons (28.83%), and also β-ocimene (37.40%) is the major constituent, followed by caryophyllene (3.71%), myrene (3.54%) and α-pinene (3.35%). While in the essential oil isolated from fully ripe fruits collected in middle September, 74 constituents comprising 87.27% which included 20 monoterpenoids (44.71%) and 43 sesquiterpenoids (38.32%) were identified, and β-ocimene was also the major constituent (30.30%). It was also noticed that the volatile content rose along with the maturity of the fruits. The essential oil yields in the above three samples were 0.6%, 1.2% and 1.4%, respectively.

Integrated transcriptome sequencing and dynamic analysis reveal carbon source partitioning between terpenoid and oil accumulation in developing Lindera glauca fruits.

Lindera glauca fruits (LGF) with the abundance of terpenoid and oil has emerged as a novel specific material for industrial and medicinal application in China, but the complex regulatory mechanisms of carbon source partitioning into terpenoid biosynthetic pathway (TBP) and oil biosynthetic pathway (OBP) in developing LGF is still unknown. Here we perform the analysis of contents and compositions of terpenoid and oil from 7 stages of developing LGF to characterize a dramatic difference in temporal accumulative patterns. The resulting 3 crucial samples at 50, 125 and 150 days after flowering (DAF) were selected for comparative deep transcriptome analysis. By Illumina sequencing, the obtained approximately 81 million reads are assembled into 69,160 unigenes, among which 174, 71, 81 and 155 unigenes are implicated in glycolysis, pentose phosphate pathway (PPP), TBP and OBP, respectively. Integrated differential expression profiling and qRT-PCR, we specifically characterize the key enzymes and transcription factors (TFs) involved in regulating carbon allocation ratios for terpenoid or oil accumulation in developing LGF. These results contribute to our understanding of the regulatory mechanisms of carbon source partitioning between terpenoid and oil in developing LGF, and to the improvement of resource utilization and molecular breeding for L. glauca.

감태나무(Lindera glauca Blume) 에탄올 추출물의 항산화 및 인체 대장암세포 증식 억제 효과에 대한 연구

Various medicinal plants were collected, air-dried, and subjected to extraction with ethanol. Ethanol extracts were screened for their efficacies as antioxidative and antiproliferative agents against cancer cells. Among the 15 species, extract of Lindera glauca Blume stem with a total polyphenolic content of 70.99±1.88 μg/TAE μg, was found to possess high DPPH radical scavenging (IC 50 =30.54±0.62 μg/mL), nitrite scavenging (IC 50 =787.94±89.28 μg/mL), and reducing power activities (595.76±1.90 μg/mL). The antiproliferative activities of plant extracts were determined using MTT assay in human colorectal cancer cells. Extracts of stems and roots from L. glauca Blume were found to possess high anti-proliferative activities in HT-29 and HCT116 cells (IC 50 =711.52±40.27 μg/mL and IC50=85.07±4.06 μg/mL, respectively). These results suggest that L. glauca Blume extract could be a useful natural antioxidant and anticancer resource.

Transcriptome analysis of distinct Lindera glauca tissues revealed the differences in the unigenes related to terpenoid biosynthesis

The Lindera glauca, an economically and ecologically important tree species, has emerged as a novel potential plant for the intensive studies of essential oil owing to its characteristic aroma and medicinal property in distinct tissues. However, the transcriptome information and molecular research on this species is still unknown to date. To reveal the formation and accumulation mechanism of essential oil in distinct L. glauca tissues, it is crucial to analyze transcriptome and to identify the full repertoire of potential unigenes involved in terpenoid biosynthesis. In this paper, the transcriptomes of the roots, sarcocarps, stems, leaves and kernels of L. glauca were analyzed for the first time by using short-read sequencing technology (Illumina). A total of 27.2GB valid reads (the average length=92.7bp) was obtained from distinct L. glauca tissues, and then assembled de novo into 264,831 unigenes by Trinity strategy (mean size=560.2bp). The resulting 98,141 unigenes (38%) of all the assembled unigenes were annotated in multiple public databases, of which 114 potential unigenes were identified to be involved in the terpenoid biosynthetic accumulation in L. glauca. Additionally, the differential expression profiles revealed 675, 697, 432, 1702 and 844 high tissue-specificity expressions of unigenes in the roots, sarcocarps, stems, leaves and kernels of L. glauca, respectively. Overall, these obtained comprehensive unigene resources will contribute to advance the research regarding the specific plant and more specifically discovery of genes participating in the terpenoid pathway and its regulation in specific tissues of the L. glauca, but also could help the understanding of the differential accumulation of secondary metabolites in distinct plant tissues.

Flavonoids from Lindera glauca Blume as low-density lipoprotein oxidation inhibitors

In order to identify antioxidant flavonoids from Lindera glauca Blume, we performed phytochemical analysis of L. glauca Blume heartwood and isolated eight flavonoids – lindeglaucol (1), lindeglaucone (2), cilicicone B (3), tamarixetin 3-O-α-L-rhamnoside (4), procyanidin A2 (5), cinnamtannin B1 (6), cinnamtannin D1 (7), and procyanidin A1 (8) – through repeated column chromatography over silica gel (SiO2), octadecyl silica gel (ODS) and Sephadex LH-20. The chemical structures of compounds 1–8 were elucidated from spectroscopic data (NMR, IR and MS). The low-density lipoprotein oxidation inhibitory activities of the isolated compounds were evaluated in vitro by using the thiobarbituric acid reactive substances assay. Compounds 5–8 exhibited high inhibition activity, comparable to the positive control butyl hydroxyl toluene. Compounds 2 and 3 were slightly less active, while 1 and 4 expressed low activity.

New diarylpropanoids from Lindera glauca Bl. heartwood

Abstract From the heartwood of Lindera glauca Blume three new diarylpropanoids have been isolated and identified, which were named lindeglaucol, lindeglaucone, and lindeglaucoside A. Chipped heartwood was extracted repeatedly with 80% aqueous methanol (MeOH) at room temperature, and the concentrated methanolic extract was successively partitioned with ethyl acetate (EtOAc), n-butanol, and H2O. From the EtOAc fraction, three new diarylpropanoids and a known chalconoid were isolated through repeated column chromatography with silica gel, octadecyl silica gel, and Sephadex LH-20. The chemical structures of the compounds were elucidated by interpretation of extensive spectroscopic data such as nuclear magnetic resonance, fast atom bombardment mass spectroscopy, and infrared. In addition, a known chalconoid, cilicicone B, was isolated for the first time from the heartwood of L. glauca.

Optimum mixture ratio of functional Lindera glauca for culture of oyster mushroom (Pleurotus ostreatus)

This study was carried out to investigated optimum mixing ratio of Korean natural Lindera glauca for production of functional oyster mushroom. Total nitrogen and carbon source of Lindera glauca was 0.16% and 40.9%, respectively and C/N ratio was 215. Total nitrogen source and pH of substrate mixed with Lindera glauca was 2.8~3.0 and 4.8~5.0, respectively. The contents of , CaO, MgO and were increased by increasing Lindera glauca, but there was no significant difference in content. Mycerial growth was faster at Lindera glauca treatments than that of control. Yields of fruiting body was the highest at Lindera glauca 20%, and dimeter and thick of pileus were increased according to increase of Lindera glauca addition ratio. The L value of pileus was the highest at the Lindera glauca 10% during mushroom harvest, but there was no significant difference in the a-value and the b-value.

Leaf litter breakdown of <i>Phyllostachys heterocycla</i>, <i>Lithocarpus glabra</i> and <i>Lindera glauca</i> in a headwater stream of Xitiaoxi watershed, upper reaches of Taihu Basin, China

In order to explore the impact of the change of the dominant leaf litter source in stream from broad leaf trees to a bamboo tree of Phyllostachys heterocycla on headwater stream ecosystem and their associated benthic macroinvertebrates,we compared the leaf physical and chemical characters of Phyllostachys heterocycla,Lithocarpus glabra and Lindera glauca,and then evaluated the leaf litter breakdown of above three species using coarse-mesh litter bags in a headwater stream of Xitiaoxi watershed,Zhejiang Province.The concentrations of nitrogen,phosphorus and the thickness of the three categories of leaves varied significantly.The nitrogen concentration of bamboo tree leaf(30.23 g/kg) was much higher than that of L.glabra(20.98 g/kg) and L.glauca(9.69 g/kg).Moreover,the leaves of P.heterocycla(k=0.00592 d-1) decomposed faster than those of L.glabra(0.00297 d-1) and L.glauca(0.00212 d-1).No significant differences were observed in macroinvertebrates abundance and biomass among the three leaf types,however,the macroinvertebrate abundance and biomass varied significantly during the sampling period.Proportions of the functional feeding groups showed that shredders was the most abundant group,which represented 40.3% of individuals and 41.6% of the macroinvertebrate biomass,indicating it was an important component of fauna associated with litter breakdown.The dominant shredder taxon is Lepidostoma,which constructs nests based on broadleaves,and accounts for 14% of the total macroinvertebrate individuals.Because bamboo leaves are narrower,with higher concentrations of nitrogen and phosphorus,and defoliation occurs every two years.We concluded that when the leaf litter source of headwater streams dominated by bamboo leaf,it might change the concentrations of nitrogen and phosphorus in the stream water,the annual amount of leaf litter into stream,the retention time,and the macrobenthos community structure.

A new genus and three new species of Phyllocoptini (Acari: Eriophyidae: Phyllocoptinae) from the Qinling Mountains, Shaanxi Province, northwestern China

A new genus and three new species of eriophyid mites from the Qinling Mountains, Shaanxi Province, northwestern China are described and illustrated: Calvittacus regiae gen. nov. and sp. nov. on Juglans regia L. (Juglandaceae); Calepitrimerus dendrobenthamiae sp. nov. on Dendrobenthamia japonica var. chinensis (Osborn) Fang (Cornaceae) and Calepitrimerus fopingi sp. nov. on Lindera glauca (Sieb. et Zucc.) Blume (Lauraceae). All the species are vagrant on the undersurface of leaves. No apparent damages were found on the host plant. A key to the species of Calepitrimerus from China is provided.

Alkaloids From Lindera glauca, Lindera erythrocarpa, and Lindera citriodora

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAlkaloids From Lindera glauca, Lindera erythrocarpa, and Lindera citriodoraMutsuo Kozuka, Masahiko Shibakawa, Katsumi Yoshimura, Kazuko Yokoyama, Nobuko Fujiwara, Kiyoe Miyaji, and Tokunosuke SawadaCite this: J. Nat. Prod. 1984, 47, 6, 1066Publication Date (Print):November 1, 1984Publication History Published online1 July 2004Published inissue 1 November 1984https://doi.org/10.1021/np50036a045RIGHTS & PERMISSIONSArticle Views118Altmetric-Citations4LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (73 KB) Get e-Alerts Get e-Alerts