Biomedical subjects

Y Liu

Publications and source records attributed to Y Liu.

At least 415 records · Page 23Linked to original sources

PubMed2001

Activation of a mitogen-activated protein kinase pathway is involved in disease resistance in tobacco.

Hypersensitive response (HR), a form of programmed cell death, is frequently associated with plant disease resistance. It has been proposed that mitogen-activated protein kinase (MAPK) cascades regulate HR cell death based on pharmacological studies by using kinase inhibitors. However, direct evidence is lacking. Here, we demonstrate that NtMEK2, a MAPK kinase, is upstream of salicylic acid-induced protein kinase (SIPK) and wounding-induced protein kinase (WIPK), two tobacco MAPKs that are activated by various pathogens or pathogen-derived elicitors. Expression of a constitutively active mutant of NtMEK2 induces HR-like cell death in tobacco, which is preceded by the activation of endogenous SIPK and WIPK. In addition, NtMEK2-SIPK/WIPK cascade appears to control the expression of 3-hydroxy-3-methylglutaryl CoA reductase (HMGR) and l-phenylalanine ammonia lyase (PAL), two defense genes encoding key enzymes in the phytoalexin and salicylic acid biosynthesis pathways. These results demonstrate that a plant MAPK cascade controls multiple defense responses against pathogen invasion.

Agrobacterium tumefaciens↗

PubMed2001

Coiled-coil domain-mediated FRQ-FRQ interaction is essential for its circadian clock function in Neurospora.

The frequency (frq) gene, the central component of the frq-based circadian negative feedback loop, regulates various aspects of the circadian clock in NEUROSPORA: However, the biochemical function of its protein products, FRQ, is poorly understood. In this study, we demonstrated that the most conserved region of FRQ forms a coiled-coil domain. FRQ interacts with itself in vivo, and the deletion of the coiled-coil region results in loss of the interaction. Point mutations, which are designed to disrupt the coiled-coil structure, weaken or completely abolish the FRQ self-association and lead to the arrhythmicity of the overt rhythm. Mutations of the FRQ coiled-coil that inhibit self-association also prevent its interaction with two other key components of the NEUROSPORA: circadian clock, namely WC-1 and WC-2, the two PAS domain-containing transcription factors. Taken together, these data strongly suggest that the formation of the FRQ-FRQ and FRQ-WC complexes is essential for the function of the NEUROSPORA: clock.

Amino Acid Sequence↗

PubMed2001

Directed evolution of operon of trehalose-6-phosphate synthase/phosphatase from Escherichia coli.

Trehalose is a nonspecific protective agent for biomacromolecules. Trehalose-6-phosphate synthase (OtsA)/phosphatase (OtsB), which is encoded by the gene operon otsBA located at -42 of the Escherichia coli genome, is the main enzyme system that catalyzes the synthesis of trehalose in E. coli. We cloned the operon and modified it by directed evolution. Unlike in the previously reported work, we modified the whole operon and screened the positive mutant simultaneously. Thus we believe that the gene complex solves the negative effects between two enzymes if one of them diversifies its structure or functions and finds the form most suitable for trehalose synthesis. It thus mimics the natural process, in which the functional improvement of organisms is related to alterations in coordinated enzymes. The evolution procedure was carried out in a sequence of error-prone PCR, shuffling PCR, and then strict screening of the mutants. After screening of a library of more than 4000 colonies, about 15 positive colonies were analyzed, resulting in a higher concentration of trehalose than control. One of them, E. coli TS7, shows 12.3-fold higher trehalose synthesis ability than E. coli DH5alpha. In contrast, we introduced the cDNA sequence of the tps1 gene from Saccharomyces cerevisiae, which has 54% identity with the gene otsA, as one of the templates in shuffling PCR. By hybrid evolution and screening, we obtained 10 positive colonies with higher concentrations of trehalose than control. E. coli TS22 appears to have 5.3-fold higher trehalose synthesis ability than E. coli DH5alpha and 1.6-fold more than E. coli DEF3(pOTS11). This result demonstrated that coevolution and hybrid evolution, as powerful protocols in protein engineering, are effective in modifying enzyme. It indicates that repeating the process of genomic evolution in nature is feasible.

Directed Molecular Evolution↗

PubMed2001

Molecular recognition studies on supramolecular systems. 32. Molecular recognition of dyes by organoselenium-bridged bis(beta-cyclodextrin)s.

A series of novel bis(beta-cyclodextrin)s tethered with organoselenium linkers, i.e., 6,6'-(o-phenylene-diseleno)-bridged bis(beta-cyclodextrin) (2), 6,6'-[2,2'-diselenobis(benzoyloxy)]-bridged bis(beta-cyclodextrin) (3), and 6,6'-[2,2'-diselenobis[2-(benzoylamino)ethylamino]]-bridged bis(beta-cyclodextrin) (4), were synthesized from beta-cyclodextrin (1). The inclusion complexation behavior of 1-4 with some dyes, such as 8-anilinonaphthalenesulfonate (ANS), Brilliant Green, Crystal Violet, Tropaeolin OO, Auramine O, and Methyl Orange, was investigated in aqueous phosphate buffer solution (pH 7.20) at 25 degrees C by UV-vis, fluorescence, and circular dichroism spectrometry, as well as fluorescence lifetime measurements. The complex stability constants (Ks) and Gibbs free energy changes (delta Go) for the stoichiometric 1:1 inclusion complexation of 1-4 with the dyes were obtained by the spectrophotometric or spectropolarimetric titrations. The bis(beta-cyclodextrin)s 2-4 showed much higher affinities toward these guest dyes than native beta-cyclodextrin 1 with fairly good molecular selectivities. The cooperative binding abilities of these bis(beta-cyclodextrin)s are discussed from the viewpoints of size/shape-fit interaction, induced-fit concept, and multiple recognition mechanism.

Journal Article↗

PubMed2001

[Multicentre clinical trial on efficacy and safety of domestic piperacillin/tazobactam for treatment of acute bacterial infections].

OBJECTIVE: To compare the efficacy and safety of domestic piperacillin/tazobactam with those of Timentin in treatment of acute bacterial infections. METHOD: A randomized controlled multicentre trial and an opening clinical trial were conducted in 4 hospitals in Beijing. RESULT: The cure and efficacy rates in the test group were 73.0% (46/63) and 96.8% (61/63), respectively and the bacterial clearance rate was 91.7% (55/60). The cure and efficacy rates in the control group were 58.7% (37/63) and 97.7% (43/44) respectively, and the bacterial clearance rate was 87.9% (51/58). The difference between the two groups was not statistically significant. The cure rate, efficacy rate and bacterial clearance rate in the opening group were 72.7% (32/44), 97.7% (43/44) and 88.4% (38/43) respectively. No serious adverse drug reaction was found during the treatment with piperacillin/tazobactam. CONCLUSION: Domestic piperacillin/tazobactam is effective and safe for the treatment of acute bacterial infections.

Adolescent↗

PubMed2001

The Telomerase/vault-associated protein TEP1 is required for vault RNA stability and its association with the vault particle.

Vaults and telomerase are ribonucleoprotein (RNP) particles that share a common protein subunit, TEP1. Although its role in either complex has not yet been defined, TEP1 has been shown to interact with the mouse telomerase RNA and with several of the human vault RNAs in a yeast three-hybrid assay. An mTep1(-/-) mouse was previously generated which resulted in no apparent change in telomere length or telomerase activity in six generations of mTep1-deficient mice. Here we show that the levels of the telomerase RNA and its association with the telomerase RNP are also unaffected in mTep1(-/-) mice. Although vaults purified from the livers of mTep1(-/-) mice appear structurally intact by both negative stain and cryoelectron microscopy, three-dimensional reconstruction of the mTep1(-/-) vault revealed less density in the cap than previously observed for the intact rat vault. Furthermore, the absence of TEP1 completely disrupted the stable association of the vault RNA with the purified vault particle and also resulted in a decrease in the levels and stability of the vault RNA. Therefore, we have uncovered a novel role for TEP1 in vivo as an integral vault protein important for the stabilization and recruitment of the vault RNA to the vault particle.

Animals↗

PubMed2001

Structure of the human zinc finger protein HIVEP3: molecular cloning, expression, exon-intron structure, and comparison with paralogous genes HIVEP1 and HIVEP2.

Here we report the cloning and characterization of HIVEP3, the newest member in the human immunodeficiency virus type 1 enhancer-binding protein family that encodes large zinc finger proteins and regulates transcription via the kappaB enhancer motif. The largest open reading frame of HIVEP3 contains 2406 aa. and is approximately 80% identical to the mouse counterpart. The HIVEP3 gene is located in the chromosomal region 1p34 and is at least 300 kb with 10 exons. RNA studies show that multiple HIVEP3 transcripts are differentially expressed and regulated. Additionally, transcription termination occurs in the ultimate exon, exon 10, or in exon 6. Therefore, HIVEP3 may produce protein isoforms that contain or exclude the carboxyl DNA binding domain and the leucine zipper by alternative RNA splicing and differential polyadenylation. Sequence homologous to HIVEP3 exon 6 is not found in mouse nor are the paralogous genes HIVEP1 and HIVEP2. Zoo-blot analysis suggests that sequences homologous to the human exon 6 are present only in primates and cow. Therefore, a foreign DNA harboring a termination exon likely was inserted into the HIVEP3 locus relatively recently in evolution, resulting in the acquisition of novel gene regulatory mechanisms as well as the generation of structural and functional diversity.

Amino Acid Sequence↗

PubMed2001

Changes in skeletal muscle heat shock proteins: pathological significance.

In response to stress, cells rapidly produce a series of new proteins known as heat shock proteins (HSP). HSPs are considered to be molecular chaperones which play a universal role in maintaining cellular homeostasis. It is known that different HSPs are expressed in skeletal muscle, namely, small HSPs (including ubiquitin, alpha B- crystallin, HSP20 and HSP 27), HSP70, HSP60 and HSP90. Skeletal muscle is a complex and heterogeneous system in that its contractile proteins are made of different isoforms to form various muscle fibre types, and each type of muscle fibre has its own histochemical and functional characteristics. It seems that the induction of HSPs differs with muscle fibre type suggesting HSP expression is muscle fibre type specific. HSPs have been shown to respond in muscle diseases and following exercise. However, the molecular mechanisms of HSP induction, regulation and its role in maintaining the muscle function, are not completely understood. Relatively few studies of HSP have been conducted in human skeletal muscles. This review discusses the significance of changes of HSPs in skeletal muscle in both physiological and pathological conditions.

Animals↗

PubMed2001

Persistence of infectious HIV on follicular dendritic cells.

Follicular dendritic cells (FDCs) trap Ags and retain them in their native state for many months. Shortly after infection, HIV particles are trapped on FDCs and can be observed until the follicular network is destroyed. We sought to determine whether FDCs could maintain trapped virus in an infectious state for long periods of time. Because virus replication would replenish the HIV reservoir and thus falsely prolong recovery of infectious virus, we used a nonpermissive murine model to examine maintenance of HIV infectivity in vivo. We also examined human FDCs in vitro to determine whether they could maintain HIV infectivity. FDC-trapped virus remained infectious in vivo at all time points examined over a 9-mo period. Remarkably, as few as 100 FDCs were sufficient to transmit infection throughout the 9-mo period. Human FDCs maintained HIV infectivity for at least 25 days in vitro, whereas virus without FDCs lost infectivity after only a few days. These data indicate that HIV retained on FDCs can be long lived even in the absence of viral replication and suggest that FDCs stabilize and protect HIV, thus providing a long-term reservoir of infectious virus. These trapped stores of HIV may be replenished with replicating virus that persists even under highly active antiretroviral therapy and would likely be capable of causing infection on cessation of drug therapy.

Animals↗

PubMed2001

An investigation of clinical correlates of Lewy bodies in autopsy-proven Alzheimer disease.

BACKGROUND: Studies of patients meeting clinical and pathologic criteria for Alzheimer disease (AD) have not consistently found associations between the presence of Lewy bodies (LBs) at postmortem examination and a higher frequency during life of the clinical features of dementia with LBs. OBJECTIVE: To evaluate the clinical correlates of LBs in patients with AD. DESIGN AND METHODS: Fifty-one patients were diagnosed as having probable AD during life and met pathologic criteria for AD. Semiquantitative ratings for LBs were obtained in 4 brain regions: substantia nigra, cingulate, insular cortex, and hippocampus. The patients had been followed up semiannually for up to 9.9 years before death, and clinical features associated with dementia with LBs, including extrapyramidal signs and visual hallucinations, were assessed at each study visit. Logistic regression analyses determined whether patients who had LBs were more likely than those without LBs to express specific clinical signs during follow-up. Cox analyses determined whether patients with LBs developed clinical signs or died earlier. Generalized estimating equations were used to compare rates of cognitive or functional change. RESULTS: Nineteen of the 51 patients had at least 1 LB in one of the studied regions. In no case was a significant relation noted between LBs and the presence of a measured clinical sign. No LB measure was associated with an increased risk of developing any of the evaluated clinical signs earlier in the disease. There was no association between the presence of LBs and more rapid mortality or more rapid disease progression. CONCLUSIONS: In patients diagnosed as having AD during life, we did not observe a relation of LBs noted during postmortem examination with the presence of any clinical feature that we assessed or with the rapidity of disease progression. The relation between LBs and specific clinical manifestations may be tenuous in these patients.

Aged↗

PubMed2001

Maternal multivitamin use and orofacial clefts in offspring.

BACKGROUND: Cleft lip with or without cleft palate (CLP) and cleft palate alone (CP) affect approximately 1 in 1000 infants and 1 in 2,500 infants, respectively. Studies of the relation between orofacial clefts and multivitamins or folic acid have been inconsistent. METHODS: We used data from a population-based case-control study involving 309 nonsyndromic cleft-affected births (222 with CLP, 87 with CP) and 3,029 control births from 1968 to 1980 to evaluate the relation between regular multivitamin use and the birth prevalence of orofacial clefts. RESULTS: We found a 48% risk reduction for CLP (odds ratio = 0.52, 95% confidence interval = 0.34-0.80) among mothers who used multivitamins during the periconceptional period or who started multivitamin use during the first postconceptional month, after controlling for several covariates. The risk reduction for CP was less than those for CLP (odds ratio = 0.81, 95% confidence interval = 0.44-1.52); however, a small number of CP cases limited interpretation. No risk reductions for CLP or CP were found for women who began multivitamin use in the second or third month after conception. CONCLUSIONS: The magnitude of the risk reduction in our study is comparable to those of other recent studies; our study does not support the contention that only large dosages of folic acid are needed to prevent orofacial clefts. More studies are needed to test the effects of multivitamins and varying dosages of folic acid on the recurrence and/or occurrence of orofacial clefts to provide information needed to determine possible prevention strategies. Published 2001 Wiley-Liss, Inc.

Case-Control Studies↗

PubMed2001

Evidence that increased 12-lipoxygenase activity induces apoptosis in fibroblasts.

The 12-lipoxygenase (LO) enzyme has been implicated in playing a role in pancreatic beta cell inflammatory damage and atherosclerosis. 12-LO reacts with fatty acids to form hydroperoxides which may alter cellular growth. In this study we investigated the direct effect of mouse leukocyte type 12-LO cDNA overexpression on apoptosis in Chinese hamster ovary fibroblast cells that also stably overexpress the angiotensin II type 1a receptor. CHO-AT1a cells expressing background levels of 12-LO exhibited clear increases in growth in response to angiotensin II. In contrast, the new 12-LO transfected cells (CHO-AT1a/ML12-LO cells) displayed reduced basal and angiotensin Il-induced growth compared to CHO-AT1a cells. Furthermore, serum-deprivation resulted in a significantly greater number of non-viable cells in clones having the greatest magnitude of 12-LO overexpression. These results suggested that reduction of the proliferation rate of CHO-AT1a/ML12-LO cells was due to an increasing rate of cell death. To determine whether the increase in cell death was due to apoptosis, we evaluated nuclear DNA fragmentation, cell morphologic changes, and activation of caspase-3. Cells overexpressing 12-LO cDNA displayed all these changes characteristic of apoptosis. In addition the 12-LO product, 12-hydroperoxyeicosatetraenoic acid (12-HPETE), directly induced apoptosis in CHO-AT1a cells. These results demonstrate for the first time that 12-LO activation can lead to apoptosis in fibroblasts, suggesting a role of 12-LO in leading to inflammatory mediated cellular damage.

Angiotensin II↗

PubMed2001

Promotion of S-phase entry and cell growth under serum starvation by SAG/ROC2/Rbx2/Hrt2, an E3 ubiquitin ligase component: association with inhibition of p27 accumulation.

The sensitive-to-apoptosis gene (SAG) was initially identified as a redox-inducible, apoptosis-protective protein and subsequently found to be the second family member of regulator of cullins (ROC)/RING box protein (Rbx)/Hrt, which acts as a component of E3 ubiquitin ligase. We report here that SAG promoted cell growth under serum starvation. Microinjection of SAG mRNA into quiescent NIH/3T3 cells induced S-phase entry as determined by [(3)H]-thymidine incorporation. Likewise, overexpression of SAG by either adenovirus infection of immortalized human epidermal keratinocytes (Rhek-1) or DNA transfection of SY5Y human neuroblastoma cells induced cell proliferation under serum starvation. Because cyclin-dependent kinase inhibitors (CKIs), including p21, p27, and p57, are degraded through the ubiquitin pathway, we tested whether SAG-induced cell growth is associated with CKI degradation. Although there was no significant difference in the levels of p21 and p57 between the vector controls and SAG-overexpressing cells, serum starvation induced 10- to 18-fold accumulation of p27 in control Rhek-1 cells. Accumulation of p27 was remarkably inhibited (only 2 to 5-fold) in SAG-infected cells. Inhibition of p27 accumulation was also observed in stably SAG-overexpressing SY5Y cells. Significantly, SAG-associated inhibition of p27 accumulation was largely abolished by the treatment with a proteasome inhibitor. In vivo binding of SAG and Skp2, an F-box protein that promotes p27 ubiquitination, was detected, and the binding was enhanced in SAG-overexpressing cells grown under serum starvation. Thus, SAG-induced growth with serum withdrawal appears to be associated with SAG-mediated p27 degradation. Mol. Carcinog. 30:37-46, 2001.

Animals↗

PubMed2001

Subclinical immunologic and physiologic responses in hexamethylene diisocyanate-exposed auto body shop workers.

BACKGROUND: Diisocyanates are potent sensitizing agents and currently the most commonly identified cause of occupational asthma in industrialized countries. However, diisocyanate asthma is difficult to diagnose and exposure and host risk factors are unclear. Auto body shops, one of the most common hexamethylene diisocyanate (HDI) exposure settings, are particularly difficult to study due to their small size and episodic exposures. Surveillance studies of such workers are limited. OBJECTIVES: We have initiated a cross-sectional field epidemiologic study, Survey of Painters and Repairers of Auto bodies by Yale (SPRAY), to characterize the effects of diisocyanate exposures on actively employed auto body shop workers. Methods and Results We present here questionnaire, physiologic, immunologic, and exposure data on 75 subjects enrolled in the study. No overt cases of clinically apparent diisocyanate asthma were identified based on spirometry, methacholine challenge, peak flows, and symptoms. HDI-specific lymphocyte proliferation was present in 30% of HDI-exposed workers and HDI-specific IgG in 34% of HDI-exposed workers, but they were not associated. HDI-specific IgE was detected in two workers. HDI-specific lymphocyte proliferation, increased methacholine responsiveness, and symptoms of chest tightness and shortness of breath were more common in the most heavily HDI-exposed workers, the painters. More long-term follow-up of this cohort should clarify the significance of these HDI-specific immunologic responses, physiologic changes, and symptoms. CONCLUSIONS: These findings demonstrate the presence of HDI-specific immune responses in a large proportion of healthy HDI-exposed workers.

Adolescent↗

PubMed2001

Plasmacytoma of the larynx diagnosed by fine-needle aspiration cytology: a case report.

Extramedullary plasmacytoma is a rare lesion. The use of fine-needle aspiration for diagnosis of plasmacytoma has been described in a few sporadic reports. To the best of our knowledge, none of these reports described the cytologic findings from plasmacytoma of the larynx. We report on a case of laryngeal plasmacytoma in a 79-yr-old man diagnosed by fine-needle aspiration cytology. The patient had a history of a plasmacytoma involving the sixth thoracic vertebra diagnosed in 1996, which progressed to multiple myeloma in 1997. He received treatment in the form of local radiation to the skeletal vertebrae and chemotherapy. Two years later, the patient presented with a large neck mass. Computed tomography (CT) was done at an outside facility, and the radiologic impression was of a large right glottic carcinoma with invasion into the right thyroid cartilage. Because of the history of multiple myeloma, a fine-needle aspiration (FNA) biopsy was performed of the laryngeal mass. Cytologic examination demonstrated atypical plasma cells arranged in a dissociative fashion, consistent with a plasmacytoma. Although there are previous surgical pathology reports of laryngeal plasmacytoma, to the best of our knowledge, this is the first report of plasmacytoma of the larynx diagnosed by FNA cytology.

Aged↗

PubMed2001

Cross-linked low molecular weight glycopeptide-mediated gene delivery: relationship between DNA metabolic stability and the level of transient gene expression in vivo.

DNA co-condensates were formed by reacting [125I]DNA with an admixture of a high-mannose glycopeptide (Man9-CWK(18)) and either of two poly(ethylene glycol) peptides (PEG-VS-CWK(18) or PEG-SS-CWK(18)) followed by cross-linking with 6-50 mol equiv of glutaraldehyde. [125I]DNA co-condensates were administered intravenously in mice to determine the influence of peptide DNA formulation parameters on specific targeting to Kupffer cells. Optimal targeting to Kupffer cells required the combined use of 50 mol % Man9-CWK(18) and PEG-CWK(18) to mediate specific recognition by the mannose receptor to Kupffer cells. The cellular uptake of cross-linked Man9-CWK(18)/PEG-CWK(18) DNA co-condensates was receptor mediated since Kupffer cell targeting was inhibited by pre-administration of Man-bovine serum albumin (BSA) but not BSA. An optimized formulation targeted 60% of the dose to the liver, with 80% of the liver-targeted DNA localized to Kupffer cells. Cross-linking with either 6, 15, or 50 mol equiv of glutaraldehyde led to a corresponding decrease in the metabolism rate of DNA in liver as measured by half-live- of 4, 6, and 39 h, respectively. Tail vein dosing of 50 microg of DNA co-condensates cross-linked with 6 mol equiv of glutaraldehyde produced detectable levels of human alpha1-antitrypsin in blood after 12 h, which peaked at day six and persisted for 10 days. The level of human alpha1-antitrypsin was elevated two-fold each day when dosing with DNA co-condensates cross-linked with 15 mol equiv of glutaraldehyde, revealing a correlation between the metabolic stability of the DNA in liver and level of gene expression. In addition to possessing greater metabolic stability, DNA co-condensates cross-linked with 50 mol equiv of glutaraldehyde, but lacking a targeting ligand, avoided rapid liver uptake and possessed a prolonged pharmacokinetic half-life, providing insight into a means to target DNA condensates to peripheral tissues.

Animals↗

PubMed2001

Cytological alterations in isolated hepatocytes from common carp (Cyprinus carpio L.) exposed to microcystin-LR.

Microcystin-LR (MC-LR) is the most commonly encountered of the toxic cyclic peptide hepatotoxins occurring in China. It is a model compound for toxicological studies. In this study, the toxicity of MC-LR (50 and 500 micrograms/L) on isolated carp hepatocytes was determined and the ultrastructural alterations of cells induced by MC-LR were observed. The alterations noted when hepatocytes were exposed to 50 micrograms/L MC-LR were blebbing of cell membrane, shrinking and deformation of nuclei, vesiculation and transformation into concentric membrane whorls of RER, and swelling and rearrangement of the cytoskeleton. However, when the cells were exposed to 500 micrograms/L MC-LR, broken cell membranes, nuclei and cytoskeleton could be observed. These ultrastructural changes paralleled the pathological events, which lead to apoptosis or necrosis of hepatocytes. These results suggest that disruption of the cytoskeletal structures could account for the blebbing of cell membrane and apoptosis induced by MC-LR.

Animals↗

PubMed2001

Fluorometric studies on inclusion complexation of L/D-tryptophan by beta-cyclodextrin 6-O-pyridinecarboxylates.

Novel beta-cyclodextrin (beta-CD) derivatives, bearing a nicotinic or isonicotinic moiety, have been synthesized by a convenient method in 21 and 25% yields, respectively. The stability constants (K) and Gibbs free energy changes (-DeltaG degrees ) for the inclusion complexation of beta-cyclodextrin 6-O-mono(3-pyridinecarboxylate) (1), 6-O-mono(4-pyridinecarboxylate) (2), and 6-O-monobenzoate (3) with L- and D-tryptophan have been determined by spectrofluorome try in aqueous buffer solution (pH = 7.20) at 25.0 degrees C. All of the modifications dramatically enhanced the original K for beta-CD by a factor of 30-280 and interestingly switched the original enantiomer preference for L- to D-tryptophan, thus affording the inverted enantio-selectivities of K(L)/K(D) = 2.5 for beta-CD and K(D)/K(L) = 1.2-2.1 for the modified CDs 1-3. These results are discussed from the viewpoints of the size-fit and geometrical complementary relationship between the host and guest.

Carboxylic Acids↗