Basis Of Poly Research Articles

Crystalline and local vibrations of paired bases in poly(dG)‐poly(dC) interacting with the hb‐1 hydrogen bond

Crystalline and local vibrations of paired bases in poly(dG)‐poly(dC) interacting with the hb‐1 hydrogen bond

Novel magnetic microspheres on the basis of poly(vinyl alcohol) as affinity medium for quantitative detection of glycated haemoglobin.

A water-in-oil suspension cross-linking technique using poly(vinyl alcohol) as polymer phase to prepare novel magnetic microbeads is described. By dispersing a conventional Fe3O4 pigment in the polymer phase and subsequently suspending the mixture in a vegetable oil phase with a defined viscosity, spherical magnetic microspheres are obtained. Bead sizes ranging from 1 to 50 microns and above can be obtained by exploiting well defined preparation parameters such as polymer concentration and oil and polymer viscosity. The performance of the magnetic matrices for the separation and quantification of glycated haemoglobin was tested using a m-aminophenylboronic acid matrix. The feasibility of this detection method for blood sugar diagnosis is discussed using a commercial column test kit for comparison.

95/05446 Comparison of sample preparation methods for the spectrophotometric determination of phosphorus in soil and coal fly ash

The integration of submicron poly-emitter transistor technology with CMOS devices, scaled down to 0·8 μm, to enhance the operating performance of BiCMOS ASICs in the GHz range, is described. It enables incorporation of npn, NMOS and PMOS transistors, Schottky diodes, polysilicon resistors and lateral fuses. The proposed process can facilitate CMOS, TTL and ECL signal levels on the same chip. To make the process more consistent and easy, the 19 masking steps are incorporated; most of them are noncritical oversized implant masks. N+ and P+ buried twin wells are formed for low isolation spacings along with their respective N and P epitaxial layers, to eliminate latchup susceptibility.The process includes some special features to increase the layout density and to reduce the parasitic capacitances. This is achieved by using sidewall spacers for polysilicon, self aligned vertical npn transistor structures and undoped polysilicon trench isolations. To obtain high fT (cut-off frequency) in the npn bipolar transistor, P+ poly base, N+ poly emitter and shallow junctions are incorporated. Titanium salicidation of N+ and P+ polysilicon is proposed while, on the source-drain of MOS transistors, a 20 nm thick TiW barrier layer deposition is added. A multilayer interconnect technology is employed with tungsten plugging and gold metallization.The 125-step process has been simulated for oxidation, impurity drive-in schedules and 12 implantation schemes in order to optimize various impurity profiles. The 60 nm emitter junction depth and 160 nm base width have been controlled by mixed boron and arsenic ion implantation through a poly-emitter window. The profile of an npn bipolar device, generated by process simulator (SUPREM), is directly provided to the device simulator (SEDAN) to find various important dc characteristics. The calculated fT and early voltage of the bipolar device were more than 7 GHz and 17 V respectively. For ac analysis of the above device, an inhouse-made high-speed transistor package (HIBTRA) has been used to explain the sinusoidal and transient behaviour of the device.The submicron MOS devices have been first simulated on an inhouse device simulator (MOSKIT) to determine their characteristics such as drain current, subthreshold current, substrate current and also to compute various MOS parameters required for circuit simulation and threshold voltage adjustment implantation doses.

New polymers for biomedical applications: Synthesis and characterization of acrylic systems with pharmacological activity

The synthesis and characterization of new biocompatible “Polymeric Drugs” on the basis of poly (methacrylic esters) and poly (methacrylamides) with side substituents of pharmacological interest, with analgesic, antiinflammatory, antipyretic and antiaggregating activities, is reported. The preparation of these systems was carried out following the universal model suggested by Ringsdorf, and the polymers prepared by the free radical polymerization of the corresponding acrylic monomers were characterized by 1H- and 13C-NMR spectroscopies. Biocompatible hydrogels were prepared by free radical copolymerization of these monomers with HEMA. The characteristic copolymerization parameters and the microstructural distribution of comonomeric sequences were determined by NMR spectroscopy. The swelling behaviour of copolymer films was followed gravimetrically. Applications of polymer and copolymer systems are being tested in the fields of pharmacology and vascular surgery.

Process integration, architecture and simulation of a GHz-BiCMOS ULSI technology

The integration of submicron poly-emitter transistor technology with CMOS devices, scaled down to 0·8 μm, to enhance the operating performance of BiCMOS ASICs in the GHz range, is described. It enables incorporation of npn, NMOS and PMOS transistors, Schottky diodes, polysilicon resistors and lateral fuses. The proposed process can facilitate CMOS, TTL and ECL signal levels on the same chip. To make the process more consistent and easy, the 19 masking steps are incorporated; most of them are noncritical oversized implant masks. N + and P + buried twin wells are formed for low isolation spacings along with their respective N and P epitaxial layers, to eliminate latchup susceptibility. The process includes some special features to increase the layout density and to reduce the parasitic capacitances. This is achieved by using sidewall spacers for polysilicon, self aligned vertical npn transistor structures and undoped polysilicon trench isolations. To obtain high f T (cut-off frequency) in the npn bipolar transistor, P + poly base, N + poly emitter and shallow junctions are incorporated. Titanium salicidation of N + and P + polysilicon is proposed while, on the source-drain of MOS transistors, a 20 nm thick TiW barrier layer deposition is added. A multilayer interconnect technology is employed with tungsten plugging and gold metallization. The 125-step process has been simulated for oxidation, impurity drive-in schedules and 12 implantation schemes in order to optimize various impurity profiles. The 60 nm emitter junction depth and 160 nm base width have been controlled by mixed boron and arsenic ion implantation through a poly-emitter window. The profile of an npn bipolar device, generated by process simulator (SUPREM), is directly provided to the device simulator (SEDAN) to find various important dc characteristics. The calculated f T and early voltage of the bipolar device were more than 7 GHz and 17 V respectively. For ac analysis of the above device, an inhouse-made high-speed transistor package (HIBTRA) has been used to explain the sinusoidal and transient behaviour of the device. The submicron MOS devices have been first simulated on an inhouse device simulator (MOSKIT) to determine their characteristics such as drain current, subthreshold current, substrate current and also to compute various MOS parameters required for circuit simulation and threshold voltage adjustment implantation doses.

Linear dichroism demonstrates that the bases in poly[d(AC)] · poly[d(GT)] and poly[d(AG)] · poly[d(CT)] are inclined from perpendicular to the helix axis

Flow linear dichroism is used to measure specific inclinations for each of the four bases in poly[d(AC)].poly[d(GT)] and poly[d(AG)].poly[d(CT)] in both the B and A forms. For the B form in solution the bases are found to have a sizable inclination. Inclination is increased in the A form, as expected. In all cases the pyrimidines are more inclined than the purines.

Preparation of Poly(2-hydroxyethyl methacrylate)-Collagen Composites

Linear and three-dimensional polymer composites were prepared on the basis of poly(2-hydroxyethyl methacrylate)--pHEMA--and collagen. Their biological properties were tested by in vitro as well as in vivo methods. The composite material (unlike pure pHEMA) supported myoblast adhesion as well as their fusion into multinuclear myotubes in vitro. The three-dimensional polymer composites stimulated a new bone formation after their intraosseal implantation in dogs and pigs. The biomaterial itself was degraded in the host organism, in contrast to stable pHEMA.

Reactions at the hydrophilic polymer electrolyte/electrode interface

Ionically conducting hydrophilic polymer electrolytes have generated interest in the context of a variety of fundamental problems and electrochemical applications, such as power sources and sensors. Fundamental aspects of hydrophilic polymer electrolytes include conductance mechanism research, analysis of adsorptive options at the polymer electrolyte/electrode interface, catalysis of dioxygen reduction and dihydrogen oxidation at this interface and current generation mechanism in electrochemical reactions. We consider and analyse these problems for some systems on the base of poly(vinyl alcohol), polyacrylic acid, their polymers, etc.

Synthesis of poly[N5-(2-hydroxyethyl)-L-glutamines] with modified side chain

The procedure for synthesis of water-soluble polymers on the basis of poly[N5-(2-hydroxyethyl)-L-glutamine] was developed. It allows binding of various groups of interest (reactive spacers, biologically active compounds, tracers etc.) to these polymers using side chains modifications. A multi-step procedure involves partial debenzylation of poly(γ-benzyl-L-glutamate), conversion of resulting carboxyl groups to reactive succinimido ester groups, which in turn are aminolyzed by the compound of interest. The final step of the synthesis, viz., aminolysis of residual benzyl ester groups with 2-aminoethanol, leads to water-soluble modified poly[N5-(2-hydroxyethyl)-L-glutamines].

Structure of the α-form of poly[d(A)] · poly[d(T)] and related polynucleotide duplexes

The α-form of poly[d(A)] · poly[d(T)], observed in fibers at high (> 80%) relative humidity, is a 10-fold double-helical structure of pitch 3.2 nm. This new X-ray analysis shows that the two strands of the double helix are of the same kind conformationally and both B-like in containing C-2′- endo-puckered deoxyribose rings. Nevertheless, the two strands are different enough for the overall morphology of the duplex to resemble that of the heteromerous model for the drier (β) form of poly[d(A)] · poly[d(T)]in which one strand has C-2′- endo rings and the other C-3′- endo. Since the orientations of the bases in poly[d(A)] · poly[d(T)]are persistently different from those of classical B-DNA it is likely that there will be local bending (about 10 °) at the junctions between general sequence tracts and the oligo [d(A)] · oligo[d(T)]tracts that occur in some native DNAs. The conclusions about the structure of α-poly[d(A)] · poly[d(T)]are reinforced by independent analyses of similar X-ray diffraction patterns from poly[d(A)] · poly[d(U)]and poly[d(A-I)] · poly[d(C-T)].

1H two-dimensional nuclear Overhauser effect and relaxation studies of poly(dA).poly(dT)

The structure of poly(dA).poly(dT) in aqueous solution has been studied by using 1H two-dimensional nuclear Overhauser effect (2D NOE) spectroscopy and relaxation rate measurements on the imino and nonexchangeable protons. The assignments of the 1H resonances are determined from the observed cross-relaxation patterns in the 2D NOE experiments. The cross-peak intensities together with the measured relaxation rates show that the purine and pyrimidine strands in poly(dA).poly(dT) are equivalent in aqueous solution. The results are consistent with a right-handed B-form helix where the sugars on both strands are in the C2'-endo/anti configuration. These observations are inconsistent with a proposed heteronomous structure for poly(dA).poly(dT) [Arnott, S., Chandrasekaran, R., Hall, I. H., & Puigjaner, L. C. (1983) Nucleic Acids Res. 11, 4141-4155]. The measured relaxation rates also show that poly(dA).poly(dT) has fast, large-amplitude local internal motions (+/- 20-25 degrees) in solution and that the amplitudes of the base and sugar motions are similar. The motion of the bases in poly(dA).poly(dT) is also similar to that previously reported for poly(dA-dT).poly(dA-dT) and poly(dG-dC).poly(dG-dC) [Assa-Munt, N., Granot, J., Behling, R. W., & Kearns, D. R. (1984) Biochemistry 23, 944-955; Mirau, P. A., Behling, R. W., & Kearns, D. R. (1985) Biochemistry 24, 6200-6211].

Interaction of the 1 alpha,25-dihydroxyvitamin D3 receptor with RNA and synthetic polyribonucleotides.

The interaction of the 1 alpha,25-dihydroxyvitamin D3 receptor with RNA and synthetic polynucleotides has been examined by using receptor from rachitic chicken intestine. Total intestinal RNA inhibited the binding of receptor to calf thymus DNA-cellulose with an efficiency equivalent to single-stranded DNA. A comparison of the inhibitory activity of several polyribonucleotides gave the following order of activities: poly(I) = poly(G) greater than or equal to double-stranded DNA greater than single-stranded DNA = poly(U). Poly(A), poly(C), and the ribonucleoside monophosphates AMP, GMP, CMP, and UMP had minimal activity. A preference for single-stranded homopolymers was observed [i.e., poly(I) and poly(U) were active, whereas poly(I):poly(C) and poly(U):poly(A) were not]. The ability of nucleic acids to displace receptor from DNA-cellulose was also measured. Both poly(G) and poly(I) were more active than double-stranded DNA in this assay. Furthermore, differences were noted between intestinal RNA fractions separated on the basis of poly(A) content. Receptor also bound to immobilized intestinal RNA and polynucleotides. The KCl concentration necessary to disrupt binding to a given polynucleotide generally paralleled the activity of that molecule in DNA-cellulose inhibition and displacement assays. These results suggest that the 1 alpha,25-dihydroxyvitamin D3 receptor can interact with RNA as well as DNA.

Deuterium NMR in the solid-state and in solution of the molecular motion of the bases in poly(I) and poly(I)·poly(C)

To provide information regarding the confirmational flexibility of nucleic acids, in particular the rate and amplitude of base motions, we have observed the deuterium NMR from single-stranded and double-stranded polynucleotides. Poly(I) was deuterated at the 8-position of the base, and the deuterium NMR was examined in solution (at 23.0 and 55.4 MHz) and for hydrated and dry fibers (at 23.0 MHz). In the solid state, the deuterium signal of dry poly(I) exhibits a powder pattern with the maximal expected quadrupolar splitting, while the relatively short spin-lattice relaxation time indicates the prescence of a rapid internal reorientation of the C-D bond with an amplitude of that motion of at least ±2.4 degrees. Hydrating the poly(I) fibers to the extent of eight molecules of water per nucleotide results in the disappearance of the deuterium signal, apparently due to a decreased spin-spin relaxation time shorter than the instrumental dead-time (even using the quadrupolar echo technique); this could occur if conformational fluctuations are occuring at a rate comparable to the deuterium quadrupole interaction strength, i.e., 175 kHz. In solution, a theoretical fit to the measured Lorentzian linewidths and spin-lattice relaxation times necessitates the inclusion of at least two motional correlation times, with a subnanosecond internal motion. Double-stranded poly(I)·poly(C) yielded a solid state spectrum similar to poly(I), albeit with a longer T 1, which reduced the lower limit for the amplitude of an internal motion to ±1.9 degrees. The 2H signal from the poly(I)·poly(C), hydrated to a degree of approx. eight molecules of water per base pair, retained its solid-state lineshape (with a reduced T 1 value, indicating increased internal mobility of the bases with a lower limit on amplitude of ±4.7°). In solution, however, the 2H-NMR signal from poly(I)·poly(C) became virtually undetectable, even in solid-echo experiments, when the echo was observed after 52 μs. This indicates that the spin-spin relaxation time of the deuterium nucleus must be close to its theoretical minimum of about 9 μs, and the correlation time for an isotropic reorientation of the C-D vector can be estimated to be between 0.2 and 200μs.

Properties of Cross‐Linked Positive Acting X‐Ray Resists Fabricated on the Basis of Poly(methylmethacrylate‐co‐methacrylyl Chloride)

Copolymers of methylmethacrylate (MMA) and methacrylyl chloride (MACl) were cross‐linked under various conditions, in order to obtain intermolecularly cross‐linked polymeric networks having different cross‐linking densities (β). These materials were irradiated with x‐rays generated by an electron‐storage ring or a conventional x‐ray tube. The results showed that there is a critical dose for total solubilization, which can be used to determine the radiation sensitivity of cross‐linked resists. Both the critical dose and the sensitivity obtained from conventional exposure curves depend strongly on β. Optimum sensitivity values were obtained with slightly cross‐linked material produced from copolymers with about 4 m/o MACl. In this case, was up to five times lower than in the case of PMMA. The contrast factor, however, was not significantly affected. The technological properties of this resist were investigated by evaluating influences upon stability due to ion milling, plasma etching , and etchant, as well as by performing adhesion‐sensitive electroplating experiments. The results indicate that this material is at least as good as PMMA resist with regard to etch stability, and that it is superior as concerns adhesion behavior. The storage instability of the uncured (not yet cross‐linked) material, caused by the gradually proceeding hydrolysis of acid‐chloride groups, leads to some problems in practical applications. It was found that reproducible resist performance can only be obtained (after controlled partial conversion of the acid chloride groups) if the material is stored and cross‐linked under total exclusion of water.

Electric dichroism and birefringence of poly(ribocytidylic acid). I. Optical properties and stability

AbstractMeasurements of the uv absorption and melting profiles of poly(rC) at low‐salt conditions confirm the existence of a double‐stranded complex at low pH and imply, but do not prove, the structure proposed by Akinrimisi et al. (1963) Biochemistry 2, 340–343. Electric dichroism and birefringence provide additional supporting evidence and indicate that the complex is one in which the bases are tilted considerably from the major molecular axis. The base‐stacking tendency of single‐stranded poly(rC), unlike poly(rA), is found to be insufficient to maintain a rodlike structure; the persistence length of stacked bases in poly(rC) must be very small. The existence of an out‐of‐plane transition in poly(rC) in the vicinity of 300 nm is conclusively demonstrated by both dichroism and birefringence measurements.

Some new developments in the field of reactive polymers and immobilized enzymes

AbstractA review of reactive carriers and immobilized enzymes describing the latest developments in the authors' laboratories is presented. Slightly basic and amphoteric reactive carriers were synthesized on the basis of poly (ethylene imine), and neutral hydrophilic carriers were obtained on the basis of polyethers. A new possibility for the Ugi reaction including carbon dioxide as the fifth component in this reaction is shown. Crosslinked acrylic acid–styrene copolymers and also poly(vinyl alcohol) were used for the introduction of maleimide groups, giving polymers with a specific reactivity towards SH‐groups containing enzymes resp. thiolated enzymes. A poly(vinyl alcohol) containing fiber material, synthetic pulp, was modified with diazonium groups and used for the immobilization of different enzymes. The properties of the immobilized enzymes were investigated.

Polarography of polynucleotides: Nonreducibility of double-stranded poly(guanylic acid) · poly(cytidylic acid)

It has been shown that the thermally labile double-stranded polyribonucleotides poly(adenylic acid) · poly(uridylic acid) and poly(cytidylic acid) · poly(inosinic acid) produce differential pulse polarographic (DPP) peaks analogous to the DPP peak II of double-stranded deoxyribonucleic acid. On the other hand the thermally most stable poly(guanylic acid) · poly(cytidylic acid) is DPP inactive. The DPP inactivity of the latter double-stranded polynucleotide has been observed under a wide variety of conditions (pH, μ and temperature). A.c. polarographic and normal pulse polarographic measurements at DME and linear sweep voltammetry at HMDE have shown that the observed DPP inactivity of this polynucleotide may be connected with its desorption from the electrode at potentials more positive than those of DNA desorption. It has been assumed that this behaviour is caused by too small an amount of bases in poly(guanylic acid) · poly(cytidylic acid) primarily available for the interaction with the electrode surface. It has been demonstrated that DPP sensitively reflects formation of the double-stranded polyribunocleotides. In the case of poly(adenylic acid) · poly(uridylic acid) and poly(guanylic acid) · poly(cytidylic acid) it is possible to detect traces of single-stranded material in a double-stranded polynucleotide sample.

The molecular electrostatic potential of the B-DNA helix. VI. The regions of the base pairs in poly (dG.dC) and poly (dA.dT).

The evaluation of the electrostatic molecular potential at important nucleophilic sites of the purine and pyrimidine bases in poly (dG.dC) and poly (dA.dT) and of the evolution of the potential through the series free bases-nucleosides-nucleotides-single polynucleotide helices-double helices enables the interpretation of the evolution of the corresponding reactivity of the bases towards a series of electrophilic carcinogenic and mutagenic reactants.

Fractionation of plant Polyadenylated RNA on the basis of poly(A) size

Polyadenylated RNA from Vicia faba meristematic root cells was fractionated on the basis of mean poly(A) size by a thermal stepwise elution from poly(U) Sepharose. Such a procedure allowed the elimination of contaminating RNA at 30° and the collection of two populations of purified polyadenylated RNA at 40° and 50°, respectively. RNA eluting at the higher temperature carried a poly(A) segment (mean size of 100 nucleotides), twice as large as the RNA eluting at the lower temperature.

Characterization of the mRNAs for α-, β- and γ-actin

The mRNAs for α-, β- and γ-actin have been characterized with respect to molecular weight and poly(A) content. Polyacrylamide gel electrophoresis under denaturing conditions shows that the mRNA for α-actin (muscle-specific actin) is approximately 4.6 × 10 5 daltons in size, and that the mRNAs for β- and γ-actin (nonmuscle actins) are much larger, approximately 6.6 × 10 5 daltons in size. We therefore calculate that the noncoding regions of the β- and γ-actin mRNAs contain about 800 nucleotides. This is in marked contrast to the noncoding regions of α-actin mRNA which contain only about 180 nucleotides. During electrophoresis in high-resolution nondenaturing gels, the β-actin mRNA migrates slightly slower than the γ-actin mRNA. This indicates either that β-actin mRNA is about 100 nucleotides longer than γ-actin mRNA, or that these mRNAs differ in secondary structure. Fractionation of actin mRNA on the basis of poly(A) content shows that a substantial portion of the β-actin mRNA, but very little of the α- or γ-actin mRNAs, fails to bind to oligo(dT)-cellulose. Much of this poly(A)-deficient β-actin mRNA, however, does bind to poly(U)-Sepharose, a substrate with higher affinity for short poly(A) sequences. This indicates that many of these β-actin mRNA molecules are polyadenylated, but that they have unusually short poly(A) tails. The finding that β- and γ-actins are translated from mRNAs of different electrophoretic mobility and different poly(A) content strongly suggests that these two closely related proteins are products of different genes.