Discovery of Elaphuri Davidiani Cornu-specific peptide biomarkers by peptidomics analysis-based method.

Elaphuri Davidiani Cornu (EDC) is the antler of the male Père David's deer, which has been reported to have multiple biological activities, and its use as a traditional Chinese medicine (TCM) in China has been known for thousands of years. However, EDC is difficult to distinguish from other related species-derived antlers in powder or extract form in TCM clinic use, such as Cervus elaphus Cornu (CEC) and Cervus nippon Cornu (CNC), both derived from Cervidae and easily confused with EDC. In this study, a strategy using peptidomics combined with mathematics set analysis was used to identify EDC-specific peptide biomarkers, and four specific peptide biomarkers (Pep-E1-E4) were identified and validated. Pep-E1, Pep-E3, and Pep-E4 could be exclusively detected in EDC samples, with relative peak areas of 0.298 ± 0.060, 0.039 ± 0.015, and 0.037 ± 0.008, whereas Pep-E2 showed relative peak area of 0.516 ± 0.101 in EDC, 0.132 ± 0.026 in CEC, and 0.136 ± 0.047 in CNC samples, respectively. These four peptides are applicable to distinguish EDC from CEC and CNC, which is of great significance for the quality control of EDC.

MRI for Diagnosing Intrauterine Adhesions.

OBJECTIVES: To prospectively assess the diagnostic accuracy of MRI and transvaginal ultrasound (TVS) as well as the prognostic value of MRI for intrauterine adhesions (IUAs), using hysteroscopy as the reference standard. DESIGN: Prospective observational study. SETTING: Tertiary medical centre. PATIENT(S): Ninety-two women with amenorrhea, hypomenorrhea, subfertility, or recurrent pregnancy loss who underwent MRI and in whom Asherman's syndrome was suspected upon TVS. INTERVENTION(S): MRI and TVS were conducted approximately 1 week before hysteroscopy. METHODS: Ninety-two patients suspected of having Asherman's syndrome were examined by MRI and TVS within 7 days of an upcoming hysteroscopy. All hysteroscopy procedures were performed during the early proliferative phase of the menstrual cycle. All hysteroscopic diagnoses were performed by an experienced expert. All MRIs were read by 2 experienced, blinded radiologists. RESULTS: MRI was highly accurate (94.57%), sensitive (98.8%), and specific (42.9%) for diagnosing IUAs with a positive predictive value of 95.5% and a negative predictive value of 75%. The diagnostic values of MRI and TVS were significantly different according to McNemar tests. Junctional zone signal and junctional zone alterations correlated with the stage of IUAs. CONCLUSION: MRI is markedly superior to TVS in terms of diagnostic accuracy for IUAs, with total agreement with hysteroscopic findings. However, the main advantage of MRI is that, unlike TVS and hysterosalpingography, it can be used to assess the risk of hysteroscopy and to predict postoperative recovery and future pregnancy based on the uterine junctional zone.

Genome-Wide Analysis of MYB Transcription Factors and Screening of MYBs Involved in the Red Color Formation in Rhododendron delavayi.

Flower color is one of the crucial traits of ornamental plants. Rhododendron delavayi Franch. is a famous ornamental plant species distributed in the mountain areas of Southwest China. This plant has red inflorescence and young branchlets. However, the molecular basis of the color formation of R. delavayi is unclear. In this study, 184 MYB genes were identified based on the released genome of R. delavayi. These genes included 78 1R-MYB, 101 R2R3-MYB, 4 3R-MYB, and 1 4R-MYB. The MYBs were divided into 35 subgroups using phylogenetic analysis of the MYBs of Arabidopsis thaliana. The members of the same subgroup in R. delavayi had similar conserved domains and motifs, gene structures, and promoter cis-acting elements, which indicate their relatively conserved function. In addition, transcriptome based on unique molecular identifier strategy and color difference of the spotted petals, unspotted petals, spotted throat, unspotted throat, and branchlet cortex were detected. Results showed significant differences in the expression levels of R2R3-MYB genes. Weighted co-expression network analysis between transcriptome and chromatic aberration values of five types of red samples showed that the MYBs were the most important TFs involved in the color formation, of which seven were R2R3-MYB, and three were 1R-MYB. Two R2R3-MYB (DUH019226.1 and DUH019400.1) had the highest connectivity in the whole regulation network, and they were identified as hub genes for red color formation. These two MYB hub genes provide references for the study of transcriptional regulation of the red color formation of R. delavayi.

Mitochondrial DNA Copy Number in Rett Syndrome Caused by Methyl-CpG-Binding Protein-2 Variants.

OBJECTIVE: To determine changes in mitochondrial DNA (mtDNA) copy number in peripheral blood in Rett syndrome caused by methyl-CpG-binding protein-2 (MECP2) variants and explore the mechanism of mitochondrial dysfunction in Rett syndrome. STUDY DESIGN: Female patients who were diagnosed with Rett syndrome and had an MECP2 variant (n = 142) were recruited in this study, along with the same number of age- and sex-matched healthy controls. MtDNA copy number was quantified by real-time quantitative polymerase chain reaction with TaqMan probes. The differences in mtDNA copy number between the Rett syndrome group and the control group were analyzed using the independent-samples t test. Linear regression, biserial correlation analysis, and one-way ANOVA were applied for the correlations between mtDNA copy number and age, clinical severity, variant types, functional domains, and hot-spot variants. RESULTS: MtDNA copy number was found to be significantly increased in the patients with Rett syndrome with MECP2 gene variants compared with the control subjects. Age, clinical severity, variant types, functional domains, and hot-spot variants were not related to mtDNA copy number in patients with Rett syndrome. CONCLUSIONS: MtDNA copy number is increased significantly in patients with Rett syndrome, suggesting that changes in mitochondrial function in Rett syndrome trigger a compensatory increase in mtDNA copy number and providing new possibilities for treating Rett syndrome, such as mitochondria-targeted therapies.

Mannose-Binding Lectin Possesses Agglutination Activity and Promotes Opsonophagocytosis of Macrophages with Calreticulin Interaction in an Early Vertebrate.

The innate immune system is an ancient defense system in the process of biological evolution, which can quickly and efficiently resist pathogen infection. In mammals, mannose-binding lectin (MBL) is a key molecule in the innate immune and plays an essential role in the first line of host defense against pathogenic bacteria. However, the evolutionary origins and ancient roles of immune defense of MBL and its mechanism in clearance of microbial pathogens are still unclear, especially in early vertebrates. In this study, Oreochromis niloticus MBL (OnMBL) was successfully isolated and purified from the serum of Nile tilapia (O. niloticus). The OnMBL was able to bind and agglutinate with two important pathogens of tilapia, Streptococcus agalactiae and Aeromonas hydrophila Interestingly, the OnMBL was able to significantly inhibit the proliferation of pathogenic bacteria and reduce the inflammatory response. Upon bacterial challenge, the downregulation of OnMBL expression by RNA interference could lead to rapid proliferation of the pathogenic bacteria, ultimately resulting in tilapia death. However, the phenotype was rescued by reinjection of the OnMBL, which restored the healthy status of the knockdown tilapia. Moreover, a mechanistic analysis revealed that the OnMBL could clear pathogenic bacteria by collaborating with cell-surface calreticulin to facilitate phagocytosis in a complement activation-independent manner. To our knowledge, these results provide the first evidence on the antibacterial response mechanism of MBL performing evolutionary conserved function to promote opsonophagocytosis of macrophages in early vertebrates and reveals new insights into the understanding of the evolutionary origins and ancient roles basis of the C-type lectins in the innate immune defense.

[Textual and information research of classical prescription Mijiao Pills].

Elaphurus davidianus( Milu),a rare animal unique to China,has been used as medicine for more than a thousand years,but the extinction of Milu in modern times resulted in the unavailability of related medical products. Today,the reintroduction of Milu population makes it possible to restore its medicinal usage. The resource reserves of Cervi Cornu,the natural shedding product from Milu,are increasing with the expansion of the population,allowing it to be fully utilized in the medical field. Mijiao Pills,first recorded in Important Prescriptions Worth a Thousand Gold for Emergency( Bei Ji Qian Jin Yao Fang) by Sun Simiao in the Tang Dynasty,is the first Chinese medicinal prescription with Cervi Cornu as the sovereign medicinal,which is effective in tonifying. Its composition,preparation,efficacy and indications,and administration are described in detail in the Important Prescriptions Worth a Thousand Gold for Emergency,which however,have changed significantly over the thousands of years,seriously affecting the clinical application of this classical prescription and related product development. Therefore,the key information of this prescription should be systematically collated and summarized. According to the principles of textual research on key information in ancient classical prescriptions promulgated by relevant authorities,this paper reviewed ancient Chinese medical books of the past dynasties,modern literature,as well as the Pharmacopoeia of the People's Republic of China( 2020 Version) to figure out such key information as the source,historical evolution,original plants and animals and their processing,dosage,preparation,and usage of Mijiao Pills. This paper aimed to provide a basis for the clinical application of Mijiao Pills and subsequent product development,thus facilitating the development and utilization of this precious medicinal animal resource.

[Regional differences of nucleosides and amino acids in Elaphuri Davidiani Cornu].

In order to reveal the regional characteristics of nucleosides and amino acids in Elaphuri Davidiani Cornu,39 samples of Elaphuri Davidiani Cornu collected from 4 different regions were analyzed by UPLC-QTRAP ~®/MS2 method followed by orthogonal partial least-squares discrimination analysis( OPLS-DA) and cluster analysis( CA). The results showed all the samples contained abundant nucleosides and amino acids,with the total content of 45. 09 µg·g~(-1) and 634. 80 µg·g-1,respectively. The samples presented significant regional differences in the contents of individual components,and the main differential components included Ura,Hpro,Thr,Glu,G5 P,2'-dG,Adeno,Met,Ade,Gln,Orni,Phe,2'-dA,Hit,Lys,and Ile. Among them,Ura,Met,Glu,and Ile had the highest content in the samples from Dafeng in Jiangsu,Qinhu in Jiangsu,Beijing,and Shishou in Hubei,respectively. OPLS-DA and CA demonstrated that all the samples of Elaphuri Davidiani Cornu could be divided into three categories,reflecting the regional characteristics. The results indicated that the accumulation of nucleosides and amino acids in Elaphuri Davidiani Cornu was closely related to its habitat,providing a useful reference for the research on the quality formation,quality evaluation and control,as well as the comprehensive utilization of Elaphuri Davidiani Cornu. The findings suggested that the content factors of Ura,Met,Glu,and Ile could be included into the quality standard system of Elaphuri Davidiani Cornu as the characteristics of medicinal materials from different regions.

Expression and functional analysis of Nile tilapia transferrin receptors (TfRs) in host resistance to pathogenic bacteria and iron ion metabolism.

Transferrin receptors (TfRs) play an essential role in iron-withholding strategy, and are involved in immune response against bacterial infection. In this study, the transferrin receptor 1 (OnTfR1) and transferrin receptor 2 (OnTfR2) genes are identified and characterized in Nile tilapia (Oreochromis niloticus). The open reading frames of OnTfR1 and OnTfR2 are 2220 and 2343 bp of nucleotide sequence, encoding 739 and 780 amino acids, respectively. The deduced proteins of OnTfR1 and OnTfR2 are highly homologous to those of other species, containing three conserved TfR superfamily domains (PA TfR domain, M28 TfR domain and TfR dimer domain). Expression analyses of OnTfRs in the healthy tilapia reveal that the OnTfR1 and OnTfR2 transcripts are the most abundant in the liver. The in vivo studies show that the expressions of OnTfRs are significantly up-regulate in liver and spleen, following infections of Streptococcus agalactiae and Aeromonas hydrophila. In addition, the in vitro studies reveal that the up-regulations of OnTfR expressions are also significant in monocytes/macrophages and hepatocytes upon the stimulations of S. agalactiae and A. hydrophila. Moreover, the iron ion (Fe3+) could significantly increase the expressions of OnTfRs in monocytes/macrophages and hepatocytes. Taken together, the present study indicates that OnTfRs may be involved in host defense against bacterial infection and possess the function of combining or transporting iron ions in Nile tilapia.

A microfibril-associated glycoprotein 4 (MFAP4) from Nile tilapia (Oreochromis niloticus) possesses agglutination and opsonization ability to bacterial pathogens.

Microfibril-associated glycoprotein 4 (MFAP4), a pattern recognition-like molecule with a fibrinogen-like domain (FBG), has the ability to combine and agglutinate pathogens, playing an essential role in the first line of innate immune defense. In this study, the sequence of Nile tilapia (Oreochromis niloticus) microfibril-associated glycoprotein 4 (OnMFAP4) open reading frame (ORF) was amplified and identified. The ORF of OnMFAP4 is 720 bp of nucleotides and codes for 239 amino acids. Spatial mRNA encoding analysis indicated that OnMFAP4 was highly produced in liver, intestine and head kidney in healthy tilapia, and with the lowest expression in muscle. After challenges with Streptococcus agalactiae (S. agalactiae) and Aeromonas hydrophila (A. hydrophila), the expression of OnMFAP4 mRNA was prominently produced in the liver, spleen and head kidney. The up-regulation of OnMFAP4 expression was also presented in head kidney monocytes/macrophages (MO/MΦ) and hepatocytes. Recombinant OnMFAP4 ((r)OnMFAP4) could bind and agglutinate both bacterial pathogens. Moreover, (r)OnMFAP4 could take part in the modulation of inflammation and phagocytosis. In conclusion, this study revealed that OnMFAP4 might take effect in host defense against bacterial infection in Nile tilapia, with agglutination and opsonization capability to bacterial pathogens.

Purification and functional characterization of serum transferrin from Nile tilapia (Oreochromis niloticus).

Transferrin (TF), an iron-binding multifunctional protein, could participate in the iron-withholding strategy, an effective antimicrobial defense mechanism in innate immunity, and is involved in host defense against pathogenic infection. In this study, a TF homologue (OnTF) was purified from serum of Nile tilapia (Oreochromis niloticus) through a two-step affinity chromatography, and characterized its antibacterial function and the role in inflammatory response. The identification by mass spectrometry showed that peptide sequence of the purified OnTF was highly consistent with its amino acids sequence, containing two conserved iron binding lobes: N-lobe and C-lobe. The native OnTF was able to bond iron ions, and possessed capability to inhibit the growth of both bacterial pathogens (Streptococcus agalactiae and Aeromonas hydrophila) in vitro. Upon infections of S. agalactiae and A. hydrophila, the expression of OnTF protein was significantly up-regulated in vivo and in vitro. In addition, the OnTF participated in the regulation of inflammation, migration, and enhancement of phagocytosis and respiratory burst activity in head kidney macrophages/monocytes. Taken together, the results of this study indicated that OnTF is likely to involve in innate immunity to play a role in host defense against bacterial infection in Nile tilapia.

Functional characterization of a mannose-binding lectin (MBL) from Nile tilapia (Oreochromis niloticus) in non-specific cell immunity and apoptosis in monocytes/macrophages.

Mannose-binding lectin (MBL), a soluble pattern recognition receptor, is able to recognize antigen and participate in non-specific cell immunity, such as regulation of inflammation, migration, opsonization, phagocytosis and killing, which plays an important role in innate immunity. In this study, we have investigated the contributing mechanisms and effects of MBL on the cell immunity of Nile tilapia (Oreochromis niloticus) monocytes/macrophages. The mRNA expression level of OnMBL was significantly up-regulated in monocytes/macrophages after in vitro bacterial infection (Streptococcus agalactiae and Aeromonas hydrophila). Recombinant OnMBL ((r)OnMBL) protein could participate in the regulation of inflammation, migration, and enhancement of phagocytosis and respiratory burst activity in monocytes/macrophages. Moreover, the (r)OnMBL could induce the apoptosis of monocytes/macrophages. Taken together, the results of this study indicated that OnMBL is likely to involve in immune regulation, which may play an important role in host defense of innate immunity in Nile tilapia.

Expression and functional characterization of a mannose-binding lectin-associated serine protease-1 (MASP-1) from Nile tilapia (Oreochromis niloticus) in host defense against bacterial infection.

Mannose-binding lectin-associated serine protease-1 (MASP-1), a multifunctional serine protease, plays an important role in innate immunity which is capable of activating the lectin pathway of the complement system and also triggering coagulation cascade system. In this study, a MASP-1 homolog (OnMASP-1) was identified from Nile tilapia (Oreochromis niloticus) and characterized at expression and inflammation functional levels. The open reading frame (ORF) of OnMASP-1 is 2187 bp of nucleotide sequence encoding a polypeptide of 728 amino acids. The deduced amino acid sequence has 6 characteristic structures, including two C1r/C1s-Uegf-BMP domains (CUB), one epidermal growth factor domain (EGF), two complement control protein domains (CCP) and a catalytic serine protease domain (SP). Expression analysis revealed that the OnMASP-1 was highly expressed in the liver, and widely exhibited in other tissues containing intestine, spleen and kidney. In addition, the OnMASP-1 expression was significantly up-regulated in spleen and head kidney following challenges with Streptococcus agalactiae and Aeromonas hydrophila. The up-regulations of OnMASP-1 mRNA and protein expression were also demonstrated in hepatocytes and monocytes/macrophages in vitro stimulation with S. agalactiae and A. hydrophila. Recombinant OnMASP-1 protein was likely to participate in the regulation of inflammatory and migration reaction by monocytes/macrophages. These results indicated that OnMASP-1, playing an important role in innate immunity, was likely to involve in host defense against bacterial infection in Nile tilapia.

Increased serum exosomal miR-134 expression in the acute ischemic stroke patients.

BACKGROUND: The exosomal miRNAs have been emerged as biomarkers and therapeutic targets for various diseases, however, the function of exosomal miRNAs in stroke remains largely unknown. METHODS: The blood samples from acute ischemic stroke (AIS) patients and normal controls were collected. The exosomes were isolated from the blood samples, which were confirmed by electron microscopy and western blot with the specific exosomes biomarker CD9, CD63 and Tsg101. RESULTS: RT-qPCR analysis showed that exosomal miR-134 was significantly increased in AIS patients within 24 h after stroke onset compared with that of control group. Highly expressed exosomal miR-134 was correlated with the National Institutes of Health Stroke Scale (NIHSS) scores, infarct volume and positively associated with the worse prognosis of the stroke patients. Additionally, the exosomal miR-134 was strong positively correlated with the expression of serum interleukin 6 (IL-6) and plasma high-sensitivity C relative protein (hs-CRP). The receiver operating characteristic (ROC) curve suggested that miR-134 might be a potential factor to discriminate AIS patients from non-stroke controls. CONCLUSIONS: The exosomal miR-134 as a possible novel biomarker for the diagnosis and prognosis of stroke.

Community-based interventions to enhance knowledge, protective attitudes and behaviors towards canine rabies: results from a health communication intervention study in Guangxi, China.

BACKGROUND: In China canine rabies poses a serious public health problem in that human mortality ranks the second highest globally. While rabies health education interventions are advocated by WHO to be critical components of modern rabies control and prevention programs, available studies have not adequately investigated the relative efficacy of their implementation in at-risk populations. This study aims to measure and compare the effect on knowledge and protective behavior towards rabies of health education interventions that include a novel Short Messaging Service via cell phone (SMS) and rabies health information sessions (IS). METHODS: The study used a between-subject design involving repeated measures of rabies-related KAP (knowledge, attitude and practice). A total of 350 randomly selected villagers were randomly allocated into three intervention (SMS, IS and SMS + IS) and one control group. The content of SMS and IS covered topics about rabies prevention and route of transmission. The SMS intervention consisted of ten separate messages delivered three times two weeks after the pretest; the IS intervention was conducted once immediately after the pretest. A validated questionnaire was used to capture demographic information and KAP information. Ordinary Least Squares regression was used to contrast the effects of interventions. RESULTS: Our results indicate that overall SMS outperforms IS at improving knowledge and protective behavior against rabies. Our results suggest that a combined intervention of SMS and IS can result in higher scores than any of the two in isolation. The impact of SMS, IS and SMS + IS is greatest on knowledge, followed by attitude and practice scores. CONCLUSION: This study demonstrated that health communication modes based on SMS, IS and a combination of the two are all effective to improve rabies-related KAP in the short term. These findings highlight the potential usefulness of SMS as an additional tool for public health communication and promotion; further studies are needed to investigate the long term benefits of these interventions on the reduction of dog bites and resulting human rabies incidence.

Supramolecular structure of self-assembled monolayers of ferrocenyl terminated n-alkanethiolates on gold surfaces.

It is important to understand the structure of redox-active self-assembled monolayers (SAMs) down to the atomic scale, since these SAMS are widely used as model systems in studies of mechanisms of charge transport or to realize electronic functionality in molecular electronic devices. We studied the supramolecular structure of SAMs of n-alkanethiolates with ferrocenyl (Fc) end groups (S(CH2)nFc, n = 3 or 4) on Au(111) by scanning tunneling microscopy (STM). In this system, the tilt angle of the Fc units with respect to the surface normal (α) depends on the value of n because the Au-S-C bond angle is fixed. The ordered domains of the SAMs were imaged by STM after annealing at 70 °C at ultrahigh vacuum conditions. High resolution electron energy loss spectroscopy (HREELS) and cyclic voltammetry show that this annealing step only removed physisorbed material and did not affect the structure of the SAM. The STM images revealed the presence of row defects at intervals of 4 nm, that is, six molecules. We determined by near edge X-ray absorption fine structure spectroscopy (NEXAFS) that the Fc units of the SAMs of SC3Fc are more parallel to the Au(111) plane with a tilt angle α = 60.2° than the Fc units of SC4Fc SAMs (α = 45.4°). These tilt angles are remarkably close to the tilt angles measured by X-ray diffraction data of bulk crystals (bc-plane). Based on our data, we conclude that the molecules are standing up and the SAMs pack into lattices that are distorted from their bulk crystal structures (because of the build-up stain due to the differences in size between the Fc units and thiolate anchoring groups).

[ApoB gene genetic polymorphism of Han nationality and Mongolian nationality in midwest area of Inner Mongolia].

OBJECTIVE: To study ApoB gene genetic polymorphism of Han nationality and Mongolian nationality in midwest area of Inner Mongolia. METHODS: Some unrelated individuals of Han nationality and Mongolian nationality in midwest area of Inner Mongolia were selected. Polymerase chain reaction-restriction fragment length polymorphism technology was used to check the presence of Xba I (X+) and EcoR I (E-) sites of rare alleles. The genotype frequency, allelic frequency and population genetics parameters were calculated. RESULTS: The frequencies of Xba I (X+) and EcoR I (E-) rare alleles were 2% and 4.6% in Han population. There was no Xba I (X+) or EcoR I (E-) rare alleles found in Mongolian nationality. CONCLUSION: The allelic frequencies of ApoB gene Xba I and EcoR I sites are very different in different races. These sites may be used in identification of ethnicity.

Automatic classification of fetal heart rate based on a multi-scale LSTM network.

Introduction: Fetal heart rate monitoring during labor can aid healthcare professionals in identifying alterations in the heart rate pattern. However, discrepancies in guidelines and obstetrician expertise present challenges in interpreting fetal heart rate, including failure to acknowledge findings or misinterpretation. Artificial intelligence has the potential to support obstetricians in diagnosing abnormal fetal heart rates. Methods: Employ preprocessing techniques to mitigate the effects of missing signals and artifacts on the model, utilize data augmentation methods to address data imbalance. Introduce a multi-scale long short-term memory neural network trained with a variety of time-scale data for automatically classifying fetal heart rate. Carried out experimental on both single and multi-scale models. Results: The results indicate that multi-scale LSTM models outperform regular LSTM models in various performance metrics. Specifically, in the single models tested, the model with a sampling rate of 10 exhibited the highest classification accuracy. The model achieves an accuracy of 85.73%, a specificity of 85.32%, and a precision of 85.53% on CTU-UHB dataset. Furthermore, the area under the receiver operating curve of 0.918 suggests that our model demonstrates a high level of credibility. Discussion: Compared to previous research, our methodology exhibits superior performance across various evaluation metrics. By incorporating alternative sampling rates into the model, we observed improvements in all performance indicators, including ACC (85.73% vs. 83.28%), SP (85.32% vs. 82.47%), PR (85.53% vs. 82.84%), recall (86.13% vs. 84.09%), F1-score (85.79% vs. 83.42%), and AUC(0.9180 vs. 0.8667). The limitations of this research include the limited consideration of pregnant women's clinical characteristics and disregard the potential impact of varying gestational weeks.

Molecular dynamics and energy landscape of decanethiolates in self-assembled monolayers on Au(111) studied by scanning tunneling microscopy.

The energetics and dynamics of the various phases of decanethiolate self-assembled monolayers on Au(111) surfaces were studied with scanning tunneling microscopy. We have observed five different phases of the decanethiolate monolayer on Au(111): four ordered phases (ß, δ, χ*, and φ) and one disordered phase (ε). We have determined the boundary free energies between the disordered and order phases by analyzing the thermally induced meandering of the domain boundaries. On the basis of these results, we are able to accurately predict the two-dimensional phase diagram of the decanethiolate/Au(111) system. The order-disorder phase transition of the χ* phase occurs at 295 K, followed by the order-disorder phase transition of the ß phase at 325 K. Above temperatures of 325 K, only the densely packed φ and disordered ε phases remain. Our findings are in good agreement with the phase diagram of the decanethiolate/Au(111) system that was put forward by Poirier et al. [Langmuir 2001, 17 (4), 1176-1183].

Dynamics of decanethiol self-assembled monolayers on Au(111) studied by time-resolved scanning tunneling microscopy.

We investigated the dynamics of decanethiol self-assembled monolayers on Au(111) surfaces using time-resolved scanning tunneling microscopy at room temperature. The expected ordered phases (ß, δ, χ*, and φ) and a disordered phase (ε) were observed. Current-time traces with the feedback loop disabled were recorded at different locations on the surface. The sulfur end group of the decanethiolate molecule exhibits a stochastic two-level switching process when the molecule is adsorbed in a (local) ß phase registry. This two-level process is attributed to the diffusion of the Au-thiolate complex between two adjacent adsorption sites. The irregular current jumps in the current-time traces recorded on the tails of decanethiolate molecules in the ordered ß, δ, and χ* phases are ascribed to wagging of the alkyl tails. Finally, the disordered phase is characterized by even larger current jumps, which indicates that the tail of the decanethiolate flips up occasionally and makes contact with the tip. Our experiments reveal that the massive dynamics of the self-assembled monolayer is due to diffusion of decanethiol-Au complexes, rather than the diffusion of decanethiolate molecules.