Molecular connectivity. 6. Examination of the parabolic relationship between molecular connectivity and biological activity.

The topologically derived, nonempirical molecular connectivity index, chi, for several classes of compounds is shown to be parabolically related to the biological activities of these compounds. Similar nonlinear relationships were previously shown between the octanol-water partition coefficients, expressed as log P, of the compounds and their biological activities. These and previous studies indicate that many physiochemical properties presently used in structure-activity studies may be intermediaries between the nonempirical molecular structure encoded in chi and measured biological activities.     

Design, synthesis, and biological evaluation of thiazoles targeting flavivirus envelope proteins

A series of third-generation analogues of methyl 4-(dibromomethyl)-2-(4-chlorophenyl)thiazole-5-carboxylate (1), which had the most potent antiviral activity among the first- and second-generation compounds, have been synthesized and tested against yellow fever virus using a cell-based assay. The compounds were designed with the objectives of improving metabolic stability, therapeutic index, and antiviral potency. The biological effects of C4 and C5 substitution were examined. The methylthio ester and the dihydroxypropylamide analogues had the best antiviral potencies and improved therapeutic indices and metabolic stabilities relative to the parent compound 1.     

Matrix metalloproteases-responsive nanomaterials for tumor targeting diagnosis and treatment

Tumour poses tremendous challenges to mankind. In various tumours, matrix metalloproteases (MMPs) are ubiquitously over expressed and participate throughout the process of tumour development. MMPs are commonly used as internal stimuli, and MMPs-responsive nanomaterials are classified into three categories according to the drug delivery process: administration and distribution to tumour, intratumoural distribution and cell internalisation, and specific drug release. First, MMPs-sensitive polyethylene glycol (PEG) de-shielding and activatable cell penetrating peptides were developed to improve the blood circulation time of drug delivery systems, thereby, enhancing tumour or stroma cells recognition and penetration. Following tumour recognition, the MMPs-sensitive and size- or morphology-changeable nanoparticles (NPs) could highly accumulate and penetrate into tumour. Lastly, several MMPs-sensitive drug release strategies were feasible for both small molecule drugs and macromolecule drugs. In conclusion, recent novel advances of MMPs-responsive nanomaterials in tumour targeting diagnosis and treatment were highlighted in this review.     

Microtiter-based assay for evaluating the biological activity of ribosome-inactivating proteins

A microtiter assay was developed to quickly measure the biological activity of ricin or other ribosome-inactivating proteins. Nuclease-treated rabbit reticulocyte lysate containing luciferase mRNA was used to measure toxin activity via inhibition of protein synthesis. The relative biological activity was determined by comparing luminescence levels in treated samples versus those of untreated controls. The amount of luciferase translated, as measured by luminescence, was inversely proportional to the toxin concentration. Linear dose response curves were generated for both class I and class II toxins. When compared to normal serum controls, specific antibody against ricin effectively inhibited ricin activity. The assay is suitable for efficient in vitro screening of therapeutics, as well as for identifying samples containing ribosome-inactivating proteins.     

Design, synthesis, and biological evaluation of antiviral agents targeting flavivirus envelope proteins

Flavivirus envelope proteins (E proteins) have been shown to play a pivotal role in virus assembly, morphogenesis, and infection of host cells. Inhibition of flavivirus infection of a host cell by means of a small molecule envelope protein antagonist is an attractive strategy for the development of antiviral agents. Virtual screening of the NCI chemical database using the dengue virus envelope protein structure revealed several hypothetical hit compounds. Bioassay results identified a class of thiazole compounds with antiviral potency in cell-based assays. Modification of these lead compounds led to a series of analogues with improved antiviral activity and decreased cytotoxicity. The most active compounds 11 and 36 were effective in the low micromolar concentration range in a cellular assay system.     

Anticancer activity of Isoliquiritigenin: biological effects and molecular mechanisms

Natural compounds derived from plants have attracted considerable attention in the scientific community due to their nontoxic nature and anti-cancer activity. Isoliquiritigenin (ISL), an active flavonoid isolated from the root of the licorice plant (Glycyrrhiza uralensis), has been previously demonstrated to have anti-inflammatory, antioxidant and tumor suppressive effects. In the past few years, the number of studies describing the effects of ISL against cancer has been gradually increased. ISL has been found to inhibit viability, proliferation, and migration of cancer cells mainly through cell cycle arrest, induction of apoptosis as well as autophagy. However, the molecular mechanisms of action are not completely comprehended. This review aimed to provide a comprehensive summary of the biological effects and molecular mechanisms of ISL against cancer.     

A reporter gene assay for determining the biological activity of therapeutic antibodies targeting TIGIT

T cell immunoglobulin and ITIM domain (TIGIT) is a novel immune checkpoint that has been considered as a target in cancer immunotherapy. Current available bioassays for measuring the biological activity of therapeutic antibodies targeting TIGIT are restricted to mechanistic investigations because donor primary T cells are highly variable. Here, we designed a reporter gene assay comprising two cell lines, namely, CHO-CD112-CD3 scFv, which stably expresses CD112 (PVRL2, nectin-2) and a membrane-bound anti-CD3 single-chain fragment variable (scFv) as the target cell, and Jurkat-NFAT-TIGIT, which stably expresses TIGIT as well as the nuclear factor of activated T-cells (NFAT) response element-controlled luciferase gene, as the effector cell. The anti-CD3 scFv situated on the target cells activates Jurkat-NFAT-TIGIT cells through binding and crosslinking CD3 molecules of the effector cell, whereas interactions between CD112 and TIGIT prevent activation. The presence of anti-TIGIT mAbs disrupts their interaction, which in turn reverses the inactivation and luciferase expression. Optimization and validation studies have demonstrated that this assay is superior in terms of specificity, accuracy, linearity, and precision. In summary, this reliable and effective reporter gene assay may potentially be utilized in lot release control, stability assays, screening, and development of novel TIGIT-targeted therapeutic antibodies.     

抗菌肽分子结构对其活性的影响

抗菌肽是一种广泛存在于生物界的抵抗病原微生物入侵的小分子多肽,是生物先天免疫的重要组成部分,具有广谱抗菌活性和抗肿瘤、抗病毒、抗真菌、抗寄生虫及免疫调节等生物活性,其区别于传统抗生素的独特作用机理,使其不易产生耐药性,是一类极具潜力的肽类抗生素.抗菌肽多样的分子结构是其产生生物活性的基础,研究表明抗菌肽的正电荷数、水脂两亲结构、保守序列、α-螺旋、二硫键、铰链结构和氨基酸构型对抗菌肽的活性至关重要.围绕以上几个方面对抗菌肽进行分子设计和改造,人们有望更加有效地提高抗菌肽的抗菌活性,获得到更加高效、低毒的抗菌肽产品.现就抗菌肽的分子结构以及结构对活性的影响等方而做一综述.     

Identification of serum proteins bound to industrial nanomaterials

Nanoparticles (NPs) are decorated with proteins and other biomolecules when they get into contact with biological systems. The presence of proteins in cell culture medium can therefore have effects on the biological outcome in cell-based tests. In this study, the manufactured nanomaterials silicon dioxide (SiO₂), titanium dioxide (TiO₂), iron-III-oxide (Fe₂O₃), and carbon black (CB) were used to study their interaction with single proteins from bovine and human plasma (albumin, fibrinogen and IgG) as well as with complete human serum. The protein binding capacity of the material was investigated and 1D gel electrophoresis was used to separate the bound proteins and to identify the bands by matrix-assisted laser desorption/ionisation-time-of-flight (MALDI-TOF) mass spectrometry.We found that the NP surface chemistry had a great impact on the amount of bound protein with distinct ligands for each of the tested particles. The hydrophobic CB NPs bound much more protein than the hydrophilic metal oxide NPs. Among the single proteins investigated, fibrinogen showed the strongest affinity for SiO₂, TiO₂ and CB NPs. The identified proteins from human serum adsorbed to these NPs were very different. Only apolipoprotein A1 was found to be adsorbed to all NPs.These studies will help to explain the different degree of biological responses observed after in vitro exposure of cells in the absence or presence of serum and might also support the interpretation of in vivo experiments were NPs come directly into contact with blood plasma.     

Efficient scavenger receptor-mediated hepatic targeting of proteins by introduction of negative charges on the proteins by aconitylation: the influence of charge density and size of the proteins molecules

The in vivo disposition characteristics of some aconitylated proteins in mice were studied after intravenous injection in relation to their molecular properties such as overall negative charge and size of the molecules. Superoxide dismutase (SOD, M_w=32 000) and bovine serum albumin (BSA, M_w=67 000) were used to produce aconitylated derivatives with a different extent of modification. Aconitylated SOD (Aco-SOD) was only moderately taken up by the liver in spite of its negative charge density, whereas aconitylated BSA (Aco-BSA) with a smaller charge density was taken up by the liver very efficiently. Aco-BSA was more rapidly cleared by the liver than succinylated BSA due to the introduction of more anionic groups, especially when the degree of modification was low. Interestingly, highly aconitylated BSAs exhibited significant accumulation in the kidney at higher doses, especially when the hepatic uptake was saturated. Further analysis that was based on a physiological pharmacokinetic model including a saturable hepatic uptake process revealed that the higher the number of negative charges on the proteins, the higher was the apparent affinity of aconitylated proteins for the hepatic SRs. In general, the affinity of aconitylated proteins was higher than that of succinylated proteins when the degree of acylation was the same. Thus, the present study indicates that apart from charge density on the proteins the molecular size of the proteins is important for SR-mediated uptake in the liver. Aconitylation of proteins seems more suitable than succinylation for targeting of proteins to the liver nonparenchymal cells, in particular, at a low degree of acylation of the proteins at which the enzymatic activity is better retained for sufficient negative charges introduced.     

Active tumor targeting of nanomaterials using folic acid, transferrin and integrin receptors

Folic acid, transferrin and integrin alpha v beta 3 (αvβ3) receptors are overexpressed in various cancer cell lines. Ligands having high affinity for these receptors are often conjugated to nanocarriers to facilitate the tumor localization of therapeutic agents. In this review the use of these ligands for targeted delivery using liposomes, dendrimers and (N-(2-hydroxypropyl) methacrylamide) (HPMA) copolymers is discussed. Emphasis is placed on discussing drug delivery systems that have been optimized for in-vitro binding as well as in-vivo pharmacokinetics. Our aim is to understand the various factors influencing the targeting ability of nanocarriers.     

A spectroscopic and molecular modeling study on novel pseudopeptides exhibiting biological activity

Abstract: A series of pseudopeptides, containing two fluorophores, such as naphthalene (N) and indole (I), and exhibiting interesting biological activity as tachykinin receptor antagonists, were investigated by electronic absorption, CD and steady-state fluorescence experiments. In polar solvents (e.g. methanol), bioactivity is coupled with a stacked, charge-separated complex between I and N, the amount of which depends on the stereochemical features and conformational mobility of the central scaffold in the molecules examined. This agrees with the idea that dipolar charged, spatially close, aromatic moieties are important topochemical elements in the mechanism of action of these receptor antagonists. Molecular mechanics calculations allowed us to build up hypothetical, low-energy conformations of a few representative pseudopeptides, whose structural features are consistent with the experimental findings.     

Estrogen receptor stereochemistry: ligand binding orientation and influence on biological activity

Racemic (Rac) 4'- and 5-deoxyindenestrol A (4'-DIA and 5-DIA), monohydroxyl analogs of the diethylstilbestrol (DES) oxidative metabolite indenestrol A (IA), were synthesized, and their enantiomers were resolved and isolated. Each compound was then tested for estrogen receptor (ER) binding affinity, uterotropic activity, and nuclear ER levels, to further define the stereochemical preference of the ER and to structually evaluate the function of each IA hydroxyl group for binding and biological activity. Competitive binding to cytosolic ER determined the relative binding affinity of racemic mixtures of 4'- and 5-DIA as 1.3 and 3.7, respectively, compared with that of DES, 286. The ER exhibited a binding preference for the S-enantiomer of both compounds, with relative binding affinities of 4'-DIA-R, 0.2; 4'-DIA-S, 1.8; 5-DIA-R, 0.9; and 5-DIA S, 5.6. 4'-DIA-Rac produced 3 times the in vivo stimulation of 5-DIA-Rac in the uterotropic bioassay (with mouse uterine doubling doses of 302.4 and 800 micrograms/kg, respectively). Nuclear ER levels measured 1 hr after in vivo treatment with either 160 micrograms/kg 4'-DIA or 80 micrograms/kg 5-DIA showed a maximum binding level of 2 (4'-DIA) and 1.5 (5-DIA) times saline control, with these doses producing levels nearly equal to that caused by a 10 micrograms/kg dose of IA. Metabolic studies were carried out by treating mice with [3H]4'- and [3H]5-DIA-Rac, to determine the differential binding affinity and biological stimulation of 4'-DIA and 5-DIA. The in vivo metabolism of the [3H]DIA compounds showed formation of [3H]IA-Rac in urine extracts, as analyzed by chiral high performance liquid chromatography. Furthermore, in vitro incubation of unlabeled 4'- and 5-DIA-Rac with mouse liver microsomes showed stereospecific metabolism, with IA-S primarily formed from 4'-DIA-Rac and IA-R from 5-DIA-Rac. Metabolism of 4'-DIA-Rac to the more active IA S-enantiomer and of 5-DIA-Rac to the less active IA R-enantiomer contributes to the different biological activities, because the ER exhibits a chiral preference for these compounds. The higher binding affinity of 5-DIA indicates that the phenyl ring hydroxyl group is required for high affinity binding; however, both hydroxyl groups are needed for subsequent biological activity. These data further suggest that the ER demonstrates stereochemical ligand binding and that IA binds in an orientation relative to 17 beta-estradiol in which the IA phenyl ring corresponds to the estradiol A-ring.     

Synthesis and biological activity of potent,low molecular weight renin inhibitors*

A series of renin inhibitors containing the dipeptide transition state mimics (2R, 4S, 5S)-5-amino-4-hydroxy-2-methyl-6-cyclohexyl hexanoic acid (Cha-Ψ[CH(OH)CH₂]Ala) and (2R, 45, 5S)-5-amino-4-hydroxy-2-isopropyl-6-cyclohexyl hexanoic acid (Cha-Ψ[CH(OH)CH₂]Val) were prepared. A structure-activity study, using pseudopeptide (Boc-Phe-His-Leu-Ψ[CH(OH)CH₂]Val-Ile-His-OH) as our lead structure, led to a new series of inhibitors, which correspond to tripeptides and contain no natural amino acids. For example, R, S-Bpma-Ape-Cha-Ψ[CH(OH)CH₂]Ala-NH₂ (IC₅₀= 1.26 nM against human plasma renin at pH 6.0; molecular weight = 564) has only two thirds of the molecular weight but twice the potency of our original lead. This new class of low molecular weight renin inhibitor displays excellent specificity toward human renin versus the related aspartic proteinase pepsin and angiotensin-1-converting enzyme. Examples are given of selected inhibitors showing encouraging evidence for intestinal absorption after intracolonic and oral administration in male Sprague-Dawley rats.     

Sialic acids: carbohydrate moieties that influence the biological and physical properties of biopharmaceutical proteins and living cells

Sialic acids are structurally diverse molecules that have important roles in the physiological reactions and characteristics of prokaryotes and eukaryotes. These include the ability to mask epitopes on underlying glycan chains and to repulse negatively charged moieties. Here, we describe the metabolism and immunological relevance of sialic acids and outline how their properties have been exploited by the pharmaceutical industry to enhance the therapeutic properties of proteins such as asparaginase and darbepoetin alpha.     

Purine and deazapurine nucleosides: synthetic approaches,molecular modelling and biological activity

A number of ligands for the adenosine binding sites has been obtained by using nucleoside convergent and divergent synthesis. Most of our nucleosides have been synthesized by coupling 2,6-dichloropurine (1), 2,6-dichloro-1-deazapurine (2), 2,6-dichloro-3-deazapurine (3) with ribose, 2- and 3-deoxyribose and 2,3-dideoxyribose derivatives. The use of these versatile synthons allowed the introduction of various substituents in 2- and/or 6-positions. The glycosylation site and the anomeric configuration of the obtained nucleosides were assigned on the basis of spectroscopic studies and confirmed by molecular models. A series of potent adenosine receptor ligands has been obtained by using divergent approaches, mostly starting from guanosine. Substitutions in 2, 6, 8, and 5' position of adenosine molecule led to ligands selective for the different adenosine receptor subtypes. Furthermore, we investigated the molecular bases of the different behavior of 2- and 8-alkynyl adenosines, by means of NMR experiments and molecular modeling studies. With docking experiments, we demonstrated that the two class of molecules should have different binding modes that explain their different degree of affinity and the shift of their activity from agonistic (2-substituted derivatives) to antagonistic (8-substituted derivatives).     

Intelligent nanomaterials for medicine: Carrier platforms and targeting strategies in the context of clinical application

Nanomedical approaches are a major transforming factor in medical diagnosis and therapies. Based on important earlier work in the field of liposomal drug delivery and metallic nanomaterials, the last decade has brought a broad array of new and improved intelligent nanoscale platforms which are not only suited to deliver drugs and imaging agents but also to carry advanced functionality including internal and external stimuli-responsiveness in a highly targeted fashion to a diseased area. This review focuses on required properties and differences of basic delivery platforms in regard to deliver smart functionality, on building blocks suited to enhance tissue-, cell- and receptor-specific targeting and on nano-bio interaction. Further it discusses advantages and disadvantages of those platforms for future clinical application with regard to the subject of complement activation and hypersensitivity reactions in particular against polyethylene glycol (PEG) and possible functionalization with nanosize switches.From the Clinical EditorThis review focuses on the properties of platforms designed to deliver smart functionality, using appropriate building blocks to enhance tissue-, cell-, and receptor-specific targeting. The authors also discuss potential complications such as complement activation and hypersensitivity reactions, and possible functionalization with nanosize switches.