Label-free emission assay of mercuric ions using DNA duplexes of poly(dT)

In this study, an assay to quantify the presence of mercuric ions and methyl mercury by double-stranded DNA containing a poly(dT) sequence was developed using a light switch compound, Ru(phen)(2)(dppz)(2+) (1), which is known to intercalate into double-stranded DNA. Upon treatment with mercuric ions, the metal-to-ligand charge transfer (MLCT) emission derived from the intercalation of 1 was reduced due to the formation of DNA duplexes containing T-Hg(2+)-T base pairs by the dehybridization of poly(dT)-poly(dA) duplexes at room temperature. As the concentration of Hg(2+) was increased, the emission of 1 gradually decreased. This label-free method had a detection limit of 5 nM. Other metal ions, such as K(+), Ag(+), Ca(2+), Mg(2+), Zn(2+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Cd(2+), Cr(3+), Fe(3+), had no significant effect on reducing emission. This emission method can differentiate matched and mismatched poly(dT) sequences based on the dehybridization rate of dsDNA and the rate decreased in the order of T(10)C·A(11)～ T(10)A·A(11) > T(10)G·A(11) > T(11)·A(11).     

Studies on peptides. CLXVII. Solid-phase syntheses and immunological properties of fragment peptides related to human malaria circumsporozoite protein

A glycine-linked tetramer of Asn-Ala-Asn-Pro, a tandem repeated sequence of malaria circumsporozoite (CS) protein, was synthesized by the Boc-based solid phase method, followed by deprotection with 1 M trimethylsilyl trifluoromethanesulfonate-thioanisole in trifluoroacetic acid. In addition, three tetramer-related peptides were similarly synthesized, i.e., a 34-residue peptide [linked with TH, a proposed T-cell epitope of CS, at the C-terminus of the tetramer], a 46-residue peptide and a 59-residue peptide [linked with HA or HA', two proposed T-cell epitopes of influenza hemagglutinin protein, at the N-terminus of the above 34-residue peptide]. Their immunological properties were examined by enzyme-linked immunosorbent assay, for which three different congenic strains of mouse were used to raise the specific antibodies. Despite conjugation of T-cell epitopes to the tetramer, the mice of low-responder strains to the tetramer failed to produce any antibody specific to the tetramer. However, with the aid of recombinant interleukin 2 as an adjuvant, the low-responder mice produced antibody with relatively high titers.     

Neomycin-neomycin dimer: an all-carbohydrate scaffold with high affinity for AT-rich DNA duplexes

A dimeric neomycin-neomycin conjugate 3 with a flexible linker, 2,2'-(ethylenedioxy)bis(ethylamine), has been synthesized and characterized. Dimer 3 can selectively bind to AT-rich DNA duplexes with high affinity. Biophysical studies have been performed between 3 and different nucleic acids with varying base composition and conformation by using ITC (isothermal calorimetry), CD (circular dichroism), FID (fluorescent intercalator displacement), and UV (ultraviolet) thermal denaturation experiments. A few conclusions can be drawn from this study: (1) FID assay with 3 and polynucleotides demonstrates the preference of 3 toward AT-rich sequences over GC-rich sequences. (2) FID assay and UV thermal denaturation experiments show that 3 has a higher affinity for the poly(dA)·poly(dT) DNA duplex than for the poly(dA)·2poly(dT) DNA triplex. Contrary to neomycin, 3 destabilizes poly(dA)·2poly(dT) triplex but stabilizes poly(dA)·poly(dT) duplex, suggesting the major groove as the binding site. (3) UV thermal denaturation studies and ITC experiments show that 3 stabilizes continuous AT-tract DNA better than DNA duplexes with alternating AT bases. (4) CD and FID titration studies show a DNA binding site size of 10-12 base pairs/drug, depending upon the structure/sequence of the duplex for AT-rich DNA duplexes. (5) FID and ITC titration between 3 and an intramolecular DNA duplex [d(5'-A(12)-x-T(12)-3'), x = hexaethylene glycol linker] results in a binding stoichiometry of 1:1 with a binding constant ～10(8) M(-1) at 100 mM KCl. (6) FID assay using 3 and 512 hairpin DNA sequences that vary in their AT base content and placement also show a higher binding selectivity of 3 toward continuous AT-rich than toward DNA duplexes with alternate AT base pairs. (7) Salt-dependent studies indicate the formation of three ion pairs during binding of the DNA duplex d[5'-A(12)-x-T(12)-3'] and 3. (8) ITC-derived binding constants between 3 and DNA duplexes have the following order: AT continuous, d[5'-G(3)A(5)T(5)C(3)-3'] > AT alternate, d[5'-G(3)(AT)(5)C(3)-3'] > GC-rich d[5'-A(3)G(5)C(5)T(3)-3']. (9) 3 binds to the AT-tract-containing DNA duplex (B* DNA, d[5'-G(3)A(5)T(5)C(3)-3']) with 1 order of magnitude higher affinity than to a DNA duplex with alternating AT base pairs (B DNA, d[5'-G(3)(AT)(5)C(3)-3']) and with almost 3 orders of magnitude higher affinity than a GC-rich DNA (A-form, d[5'-A(3)G(5)C(5)T(3)-3']).     

含有羧基配体的蝎型钒氧配合物的合成、结构及其热分解动力学

设计合成了两种新型的以聚吡唑硼酸盐、氨基酸为配体的钒氧配合物VO[phCH2CH(NH2)COO][HB(pz)3](1)和VO(3,5-Me2pz)[HB(3,5-Me2pz)3](CH3COO)(2). 通过元素分析、红外光谱对配合物进行了表征, 并利用单晶X射线衍射技术解析了它们的结构. 非等温热分解动力学研究表明, 配合物1和2的热分解反应都是分两步进行的. 通过计算, 配合物1热分解的第一步反应的可能机理为成核与生长(n=1/4); 第二步反应的可能机理为化学反应. 其非等温动力学方程分别为, dα/dT=(A/β)e-E/RT(1/4)(1-α)[-ln(1-α)]-3 和dα/dT=(A/β)e-E/RT(1-α)2. 分解反应的表观活化能分别是223.52 和331.94 kJ·mol-1; 指前因子ln(A/s-1)分别是49.67 和57.50. 配合物2 热分解的第一步反应的可能机理为化学反应; 第二步反应的可能机理为成核与生长(n=1/2). 其非等温动力学方程分别为, dα/dT=(A/β)e-E/RT(1-α)2, 和dα/dT=(A/β)e-E/RT(1/2)(1-α)[-ln(1-α)]-1. 分解反应的表观活化能分别是300.56 和444.72 kJ·mol-1; 指前因子ln(A/s-1)分别是75.53 和92.50.     

Peptide Bond Hydrolysis Catalyzed by the Wells-Dawson Zr(α(2)-P(2)W(17)O(61))(2) Polyoxometalate

In this paper we report the first example of peptide hydrolysis catalyzed by a polyoxometalate complex. A series of metal-substituted Wells-Dawson polyoxometalates were synthesized, and their hydrolytic activity toward the peptide bond in glycylglycine (GG) was examined. Among these, the Zr(IV)- and Hf(IV)-substituted ones were the most reactive. Detailed kinetic studies were performed with the Zr(IV)-substituted Wells-Dawson type polyoxometalate K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O which was shown to act as a catalyst for the hydrolysis of the peptide bond in GG. The speciation of K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O which is highly dependent on the pD, concentration, and temperature of the solution, was fully determined with the help of (31)P NMR spectroscopy and its influence on the GG hydrolysis rate was examined. The highest reaction rate (k(obs) = 9.2 (±0.2) × 10(-5) min(-1)) was observed at pD 5.0 and 60 °C. A 10-fold excess of GG was hydrolyzed in the presence of K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O proving the principles of catalysis. (13)C NMR data suggested the coordination of GG to the Zr(IV) center in K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O via its N-terminal amine group and amide carbonyl oxygen. These findings were confirmed by the inactivity of K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O toward the N-blocked analogue acetamidoglycylglycinate and the inhibitory effect of oxalic, malic, and citric acid. Triglycine, tetraglycine, and pentaglycine were also fully hydrolyzed in the presence of K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O yielding glycine as the final product of hydrolysis. K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O also exhibited hydrolytic activity toward a series of other dipeptides.     

Facile solid-phase synthesis of sulfated tyrosine-containing peptides: Part II. Total synthesis of human big gastrin-II and its C-terminal glycine-extended peptide (G34-Gly sulfate) by the solid-phase segment condensation approach

Application of the fluoren-9-ylmethoxycarbonyl (Fmoc)-based solid-phase segment condensation approach to the preparation of sulfated peptides was investigated through the synthesis of human big gastrin-II, a 34-residue sulfated tyrosine [Tyr(SO3H)]-containing peptide. Highly acid-sensitive 2-chlorotrityl resin (Clt resin) was exclusively employed as an anchor-resin for the preparation of the three peptide segments having the C-terminal Pro residue as well as of the Tyr(SO3H)-containing resin-bound segment. By using the PyBOP-mediated coupling protocol [PyBOP=benzotriazolyloxytris(pyrrolidino)phosphonium hexafluorophosphatel, we successively condensed each segment and constructed the 34-residue peptide-resin without any difficulty. The final acid treatment of the fully protected peptide-resin at low temperature (90% aqueous TFA, 0 degree C for 8 h), which can detach a Tyr(SO3H)-containing peptide from the resin and remove the protecting groups concurrently with minimum deterioration of the sulfate, afforded a crude sulfated peptide. After one-step HPLC purification, a highly homogeneous human big gastrin-II was easily obtained in 14% yield from the protected peptide-resin. The sulfate form of the C-terminal glycine-extended gastrin (G34-Gly sulfate), a posttranslational processing intermediate of gastrin-II, was also successfully prepared with the segment condensation approach (11% yield). These results demonstrated the usefulness of the segment condensation protocol for preparing large Tyr(SO3H)-containing peptides.     

Synthesis and Crystal Structure of a New Iron Complex with Cyclic Water Hexamers [Fe(CDTA)(H_2O)]·[Fe(1,10-phen)_3]·10H_2O·2OH

The title complex [Fe(CDTA)(H2O)]·[Fe(1,10-phen)3]·10H2O·2OH (CDTA = transcyclohexane-1,2-diamine-N,N,N,N′-tetraacetate) has been prepared and characterized by single-crystal X-ray diffraction analysis. The crystal adopts space group P with a = 12.793(4), b = 14.104(5), c = 17.880(5), V = 2792.2(1)3, Dc = 1.459 g/cm3, C50H66Fe2N8O21, Mr = 1226.81, F(000) = 1284, μ = 0.604 mm-1, Z = 2, R = 0.1055 and wR = 0.2581 for 8675 observed reflections (I > 2σ(I)). X-ray crystallography analysis exhibits that the title compound consists of two crystallographically independent molecules [Fe(CDTA)(H2O)] and [Fe(1,10-phen)3], and they are connected through O-H···O hydrogen bonds and π···π stacking interactions forming a 3D supramolecular structure. Interestingly, there is a cyclic water hexamer with chair conformation in this complex.     

Metal-mediated peptide assembly: use of metal coordination to change the oligomerization state of an alpha-helical coiled-coil

Metal coordination is used to alter the oligomerization state of a designed peptide structure. The 30-residue polypeptide AQ-Pal14Pal21contains two metal-binding 4-pyridylalanine (Pal) residues on its solvent-exposed surface and exists as a very stable two-stranded alpha-helical coiled-coil. Upon the addition of Pt(en)(NO3)2, a significant conformational change to a metal-bridged, four-helix bundle is seen.     

胰酶的小肽类抑制剂的研究

利用噬菌体表面展示15肽库技术对胰酶抑制剂进行了3轮特异性的筛选.从中得到18个不同的肽序列,与胰酶天然抑制剂活性部位比较,对抑制剂的活性序列进行了分析.根据分析结果合成了1个9肽,其抑制常数为89±10μmol/L.     

Influence of dT20 and [d(AT)10]2 on cisplatin hydrolysis studied by two-dimensional [1H,15N] HMQC NMR spectroscopy

The influence of the presence of DNA on the kinetics of cisplatin (cis-[PtCl2(NH3)2]) aquation (replacement of Cl- by H2O) and anation (replacement of H2O by Cl-) involved in the hydrolysis of cisplatin have been determined by two-dimensional [1H,15N] HMQC NMR spectroscopy. Single-stranded dT20 and double-stranded [d(AT)10]2 oligonucleotides were used as DNA models, avoiding guanines which are known to react rapidly with aquated cisplatin forms. Reactions starting from cis-[PtCl2(15NH3)2], or from a stoichiometric mixture of cis-[Pt(15NH3)2(H2O)2]2+ and Cl- (all 0.5 mM Pt(II); in ionic strength, adjusted to 0.095 M or 0.011 M with NaClO4, pH between 3.0 and 4.0) were followed in an NMR tube in both the absence and presence of 0.7 mM dT20 or [d(AT)10]2. In the presence of dT20, we observed a slight and ionic-strength-independent decrease (15-20 %) of the first aquation rate constant, and a more significant decrease of the second anation rate constant. The latter was more important at low ionic strength, and can be explained by efficient condensation of cis-[Pt(15NH3)2(H2O)2]2+ on the surface of single-stranded DNA, in a region depleted of chloride anions. At low ionic strength, we observed an additional set of [1H,15N] HMQC spectral signals indicative of an asymmetric species of PtN2O2 coordination, and we assigned them to phosphate-bound monoadducts of cis-[Pt(15NH3)2(H2O)2]2+. Double-stranded [d(AT)10]2 slowed down the first aquation step also by approximately 15 %; however, we could not determine the influence on the second hydrolysis step because of a significant background reaction with cis-[Pt(NH3)2(H2O)2]2+.     

Crystal structure of a novel two-dimensional supramolecular network based on polyoxoanion and yttriumIII coordination cation

A novel compound (NH4)2Y(H2O)8[PMo10V2O40]·10H2O has been prepared in an aqueous solution and characterized by elemental analysis, IR, and TG-DTG analysis. X-ray diffraction analysis was carried out on (NH4)2Y(H2O)8 [PMo10V2O40]·10H2O single crystal, which crystallizes in the monoclinic system of a space group P21/c with a=0.9871(3) nm,b=1.5424(5) nm, c=2.7924(9) nm, β= 94.183(5)° and Z=2. In the compound, a two-dimensional network is constructed by the PMo10V2O54-0 anion and the Y(H2O)83+ cation building blocks via hydrogen bonding exhibiting the porous structure.     

红色磷光喹喔啉铂(II)配合物及其有机电致发光器件的制备

利用2,3-二苯基喹喔啉和氯亚铂酸钾(K2PtCl4)反应, 合成了一种新型喹喔啉铂的配合物(DPQ)Pt(acac), 通过元素分析, 1H NMR测定对配合物结构进行了表征, 结果显示得到的是目标化合物. 利用紫外光谱和荧光光谱对配合物进行了研究. 利用该材料作为磷光染料制备了结构为ITO/NPB (21 nm) /NPB∶7%(DPQ)Pt(acac) (17.5 nm) /BCP (7 nm)/ Alq3 (21 nm)/ Mg∶Ag(10∶1)(120 nm)/Ag(10 nm)的有机电致发光器件(OLED). 结果表明, 该配合物在442和485 nm处存在单重态1MLCT(金属到配体的电荷跃迁)和三重态3MLCT的吸收峰; 在632 nm 处有较强的金属配合物三重态的磷光发射; 该器件的启动电压是5.0 V, 器件的最大亮度为1516 cd·m-2, 外量子效率为0.66%, 流明效率为0.26 lm·W-1, 是一种红色磷光材料.     

UV Raman spatially resolved melting dynamics of isotopically labeled polyalanyl peptide: slow alpha-helix melting follows 3(10)-helices and pi-bulges premelting

We used UV resonance Raman (UVRR) to examine the spatial dependence of the T-jump secondary structure relaxation of an isotopically labeled 21-residue mainly Ala peptide, AdP. The AdP penultimate Ala residues were perdeuterated, leaving the central residues hydrogenated, to allow separate monitoring of melting of the middle versus the end peptide bonds. For 5 to 30 degrees C T-jumps, the central peptide bonds show a approximately 2-fold slower relaxation time (189 +/- 31 ns) than do the exterior peptide bonds (97 +/- 15 ns). In contrast, for a 20 to 40 degrees C T-jump, the central peptide bond relaxation appears to be faster (56 +/- 6 ns) than that of the penultimate peptide bonds (131 +/- 46 ns). We show that, if the data are modeled as a two-state transition, we find that only exterior peptide bonds show anti-Arrhenius folding behavior; the middle peptide bonds show both normal Arrhenius-like folding and unfolding. This anti-Arrhenius behavior results from the involvement of pi-bulges/helices and 3(10)-helix states in the melting. The unusual temperature dependence of the (un)folding rates of the interior and exterior peptide bonds is due to the different relative (un)folding rates of 3(10)-helices, alpha-helices, and pi-bulges/helices. Pure alpha-helix unfolding rates are approximately 12-fold slower (approximately 1 micros) than that of pi-bulges and 3(10)-helices. In addition, we also find that the alpha-helix is most stable at the AdP N-terminus where eight consecutive Ala occur, whereas the three hydrophilic Arg located in the middle and at the C-terminus destabilize the alpha-helix in these regions and induce defects such as pi-bulges and 3(10)-helices.     

Incorporation of pseudoproline derivatives allows the facile synthesis of human IAPP, a highly amyloidogenic and aggregation-prone polypeptide

The efficient Fmoc solid-phase peptide synthesis of the 37-residue human Amylin and its amyloidogenic 8-37 fragment was achieved using pseudoproline (oxazolidine) dipeptide derivatives. Syntheses of hAmylin(8-37) using Fmoc amino acids produced only traces of the desired peptide. Incorporation of pseudoproline dipeptides produced the desired product with high yield and allowed for the synthesis of the full length peptide. The crude material was pure enough to allow formation of the Cys-2 to Cys-7 disulfide by air oxidation. [Structure: see text]     

Modeling nonaqueous proton wires built from helical peptides: biased proton transfer driven by helical dipoles

We report gas-phase electronic structure calculations on helical peptides that act as scaffolds for imidazole-based hydrogen-bonding networks (proton wires). We have modeled various 21-residue polyalanine peptides substituted at regular intervals with histidines (imidazole-bearing amino acids), using a hybrid approach with a semiempirical method (AM1) for peptide scaffolds and density functional theory (B3LYP) for proton wires. We have computed energy landscapes including barriers for Grotthuss-shuttling-type proton motions though wires supported on 3(10)-, α- and π-helical structures, showing the 3(10)- and α-helices to be attractive targets in terms of high proton affinities, low Grotthuss shuttling barriers, and high stabilities. Moreover, bias forces provided by the helical dipole moments were found to promote unidirectional proton translocation.     

Indium sulfide clusters integrated with 2,2'-bipyridine complexes

Supertetrahedral compounds of chalcogenometalates (T3 cluster compounds) integrated with Ni-bpy (bpy = 2,2'-bipyridine) complex were prepared by a solvothermal technique. The compound [Ni(bpy)(3)](3)[H(4)In(10)S(20)]·bpy·2EG·6H(2)O (Mb-InS-1) (EG = ethylene glycol) consists of discrete T3 clusters of [H(4)In(10)S(20)](6-) with three [Ni(bpy)(3)](2+) cations. The compound [Ni(bpy)(3)](2)[H(2)In(10)S(19)]·bpy·2HEA·2H(2)O (Mb-InS-2) (EA = ethanolamine) is a 1-D polymer, in which zigzag T3 cluster chains are charge balanced by metal-bpy complex cations. The compound [Ni(bpy)(3)](7)[H(4)In(40)S(74)]·7Hbpy·3HEA·8H(2)O (Mb-InS-3) is a 2-D T3 polymer with cation layers of [Ni(bpy)(3)](2+). Integrating M-bpy complex cations into chalcogenido structures has been made with the aim of improving the photoabsorption of the materials. The electronic spectra showed the new bands of cation-anion charge-transfer (CACT) that is mainly caused by the S···H-C(py) contacts between the InS T3 supertetrahedral clusters and the [Ni(bpy)(3)](2+) cations.     

Solid phase synthesis and opioid receptor binding properties of presumable dermorphin precursor derivatives.

Presumable dermorphin precursor peptide derivatives comprised of 35 amino acids and their fragments, which are based on the amino acid sequence determined by recombinant deoxyribonucleic acid (DNA) techniques, were synthesized by the solid phase method. A 35-residue peptide amide containing L-Ala2-dermorphin sequence at the N-terminus (1) as well as its D-Ala2 isomer (2) and the C-terminal 20-residue peptide amide were found to be unexpectedly stable against aminopeptidase M digestion and in rat brain membrane fractions mixture, suggesting that the C-terminal Glu-rich moiety of 1 and 2 serves to protect from enzymatic breakdown. In the opioid receptor binding assay, 2 showed 40 and 25-fold higher affinities than 1 for mu and delta-receptors, respectively. The N-terminal 15-residue peptide fragment of 2 showed greatly increased affinities for both receptors, being one half of those of dermorphin, whereas that of 1 showed low affinities. Opioid receptor binding properties of these synthetic peptides may be useful in investigation of the processing to dermorphin.     

Amino acid derivatives of perylenediimide and their N-H···O peptide bond dipoles-templated solid state assembly into stacks

A methodology is proposed to provide direct access in good yields to peptide residues-appended perylenediimides PDI-(Cl(4))-[Gly-Ala(OEt)](2), 2a, PDI-(Cl(4))-[Gly-Val(OEt)](2), 2b and PDI-(Cl(4))-[Gly-Gly(OEt)](2), 2c from a generic perylenediimide (PDI) platform symmetrically functionalized with carboxylic acids at the imide sites, PDI-(Cl(4))-[Gly(OH)](2), 1. The latter is obtained in good purity by a non classical two-steps route avoiding the many, notoriously cumbersome successive chromatography steps typical of PDI chemistry, and including a single final purification allowing to crystallize the water soluble pure diacid 1, of great interest in its own right for further developments in a variety of fields. Then, the synthesis, crystallization and analysis of the crystal structures of 2a and 2b reveal a common pattern of self-assembly of the outer peptide residues based on collections of parallel N-H···O peptidic hydrogen bonds running alongside stacks where the constraints imposed upon on the inner PDI skeletons by long range interaction of these parallel electric dipoles reduce the dihedral angles around the bay regions by as much as 11% down to 32°.     

若干镧系络合物的空间群

摘要 藉助模拟强度精修将九个镧系络合物晶体结构的空间群作了修正 .（ 1） NaN[Nd(DMSO)5(H2O)3]Cl3· 3H2O从 P1修正为 P;（ 2） Er(ClO4)3· 6(CH3)2NC(O)N(CH3)2从 P修正为 R;（ 3） Nd(O3SCF3)3· DMF· 6H2O从 P1修正为 R3m;(4)[NaNCCH3][Nd{S2CN(CH2CH3)2}4]从 P修正为 C 2/c;(5)[(CH3)2NCS2]3La· 2DMSO从 Cc修正为 C 2/c;（ 6） Yb(C9H7)2· 2THF从 Cc修正为 C 2/c;（ 7） [(C6H5)3Ge]2Yb· 4THF从 P21修正为 P 2;(8)TlPr(C36H44N4)2从 Pna2,修正为 Pnma;(9)[CuLaSm(C4O4)4(H2O)16]· 2H2O从 P2修正为 P2.（ 8）、（ 9）两个络合物结构从非心修正到有心时,不仅改进了键长与键角值,而且影响到分子结构特征的描述 .