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At least 829 records · Page 46Linked to original sources
PubMed1997

Colorimetric analysis of surface reactive amino groups on poly(lactic acid-co-lysine):poly(lactic acid) blends.

The quantification of functional amino (NH2) groups on poly(lactic acid-co-lysine):(poly(L-lactic acid (PLAL:PLA) blends was performed using a colorimetric assay based on the reaction of sulpho-succinimidyl-4-O-(4,4'-dimethoxytrityl)-butyrate (sulpho-SDTB) with primary amino groups. The colorimetric assay was used to assess the available reactive sites for coupling of biologically active species to PLAL. Blends were created that contained from 10 to 70 wt% poly(lactic acid-co-lysine). Bulk lysine contents within the blends were determined by amino acid analysis and ranged from 9.1 micromol g(-1) to 52.9 micromol g(-1) for blends created using PLA of 100000g mol(-1) molecular weight. Surface amino group concentrations on the same set of blends ranged from 0.23 to 1.45 nmol cm(-2). Similar surface amino groups concentrations were measured on blends using 50000, 200000 and 300000g mol(-1) poly(lactic acid). Non-specific interactions of the colorimetric assay reagents with the PLAL-containing blends were measured on blends prepared from epsilon-amino protected PLAL and 100000g mol(-1) PLA. The presence of amino groups within the top 50 angstroms was confirmed by X-ray photoelectron spectroscopy.

Amino Acids↗
PubMed2001

Brush-like branched biodegradable polyesters, part III. Protein release from microspheres of poly(vinyl alcohol)-graft-poly(D,L-lactic-co-glycolic acid).

Brush-like branched polyesters, obtained by grafting poly(lactic-co-glycolic acid), PLGA, onto water-soluble poly(vinyl alcohol) (PVAL) backbones, were investigated regarding their utility for the microencapsulation of proteins. Poly(vinyl alcohol)-graft-poly(lactic-co-glycolic acid), PVAL-g-PLGA, offers additional degrees of freedom to manipulate properties such as e.g. molecular weight, glass transition temperature and hydrophilicity. PLGA chain length was varied at a constant molecular weight (M(w)) of the PVAL backbone and secondly M(w) of the PVAL backbone was varied keeping the PLGA chain lengths constant. The most striking feature of these polymers is their high M(w). Microencapsulation of hydrophilic macromolecules, such as bovine serum albumin, ovalbumin, cytochrome c and FITC-dextran using a w/o/w double emulsion technique was investigated. Surface morphology, particle size, encapsulation efficiencies and protein release profiles were characterized as well. Microencapsulation of model compounds was feasible at temperatures of 0-4 degrees C with yields typically in the range of 60-85% and encapsulation efficiencies of 70-90%. Both, encapsulation efficiency and initial protein release (drug burst) were strongly affected by the glass transition temperature, T(g), of the polymer in contact with water, whereas the in vitro protein release profile depended on the PVAL-g-PLGA structure and composition. In contrast to PLGA, protein release patterns were mostly continuous with lower initial drug bursts. Shorter PLGA chains increased drug release in the erosion phase, whereas initial pore diffusion was affected by the M(w) of PVAL backbone. Release profiles from 2 to 12 weeks could be attained by modification of composition and molecular weight of PVAL-g-PLGA and merit further investigations under in vivo conditions. The in vitro cytotoxicity of PVAL-g-PLGA is comparable to PLGA and therefore, this new class of biodegradable polyesters has considerable potential for parenteral drug delivery systems.

Animals↗
PubMed2001

Poly(lactic acid)-poly(ethylene glycol) nanoparticles as new carriers for the delivery of plasmid DNA.

The purpose of the present work was to produce and characterize poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) nanoparticles (size lower than 300 nm) containing a high loading of plasmid DNA in a free form or co-encapsulated with either poly(vinyl alcohol) (PVA) or poly(vinylpyrrolidone) (PVP). The plasmid alone or with PVA or PVP was encapsulated by two different techniques: an optimized w/o/w emulsion-solvent evaporation technique as well as by a new w/o emulsion-solvent diffusion technique. Particle size, zeta potential, plasmid DNA loading and in vitro release were determined for the three plasmid-loaded formulations. The influence of the initial plasmid loadings (5, 10, 20 microg plasmid DNA/mg PLA-PEG) on those parameters was also investigated. The plasmid loaded into the nanoparticles and released in vitro was quantified by fluorimetry and the different molecular forms were identified by gel electrophoresis. PLA-PEG nanoparticles containing plasmid DNA in a free form or co-encapsulated with PVA or PVP were obtained in the range size of 150-300 nm and with a negative zeta potential, both parameters being affected by the preparation technique. Encapsulation efficiencies were high irrespective of the presence of PVA or PVP (60-90%) and were slightly affected by the preparation technique and by the initial loading. The final plasmid DNA loading in the nanoparticles was up to 10-12 microg plasmid DNA/mg polymer. Plasmid DNA release kinetics varied depending on the plasmid incorporation technique: nanoparticles prepared by the w/o diffusion technique released their content rapidly whereas those obtained by the w/o/w showed an initial burst followed by a slow release for at least 28 days. No significant influence of the plasmid DNA loading and of the co-encapsulation of PVP or PVA on the in vitro release rate was observed. In all cases the conversion of the supercoiled form to the open circular and linear forms was detected. In conclusion, plasmid DNA can be very efficiently encapsulated, either in a free form or in combination with PVP and PVA, into PLA-PEG nanoparticles. Additionally, depending on the processing conditions, these nanoparticles release plasmid DNA either very rapidly or in a controlled manner.

Chemical Phenomena↗
PubMed1999

Influence of formulation parameters on the characteristics of poly(D, L-lactide-co-glycolide) microspheres containing poly(L-lysine) complexed plasmid DNA.

This study describes the influence of polymer type, surfactant type/concentration, and target drug loading on the particle size, plasmid DNA (pDNA) structure, drug loading efficiency, in vitro release, and protection from DNase I degradation of poly(D, L-lactide-co-glycolide) (PLGA) microspheres containing poly(L-lysine) (PLL) complexed pDNA. PLGA microspheres containing pDNA-PLL were prepared using the water-in-oil-in-water (w-o-w) technique with poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) as surfactants in the external aqueous phase. A complex ratio of 1:0.33 (pDNA-PLL, w/w) enhanced the stability of pDNA during microsphere preparation. Higher pDNA-PLL loading efficiency (46.2%) and supercoiled structure (64.9%) of pDNA were obtained from hydrophobic PLGA (M(w) 31000) microspheres compared with hydrophilic PLGA or low-molecular-weight PLGA microspheres. The particle size decreased from 6.6 to 2.2 microm when the concentration of PVA was increased from 1 to 7%. At the same concentration of surfactant, PVA stabilized microspheres showed higher pDNA-PLL loading efficiency (46.2%) than PVP stabilized microspheres (24.1%). Encapsulated pDNA in PLGA microspheres was protected from enzymatic degradation and maintained in the supercoiled form. The pDNA-PLL microspheres showed in vitro release of 95.9 and 84.9% within 38 days from the low-molecular-weight PLGA and hydrophilic PLGA microspheres, respectively, compared to 54.2% release from the hydrophobic, higher-molecular-weight PLGA microspheres. The results suggest loading and release of pDNA-PLL complex can be influenced by surfactant concentration and polymer type.

DNA Adducts↗
PubMed1999

Fibre X-ray study of the helix-helix transitions of poly(dG-dC).poly(dG-dC).

Poly(dG-dC).poly(dG-dC) and poly(dG-m5dC).poly(dG-m5dC) present helix-helix transitions which are commonly assumed to be changes between the right-handed A- or B-DNA double helices and the left-handed Z-DNA structure. The mechanisms for such transconformations are highly improbable especially when they are supposed to be active in long polynucleotide chains organised in semicrystalline fibres. The present alternative possibility assumes that rather than the Z-DNA it is a right-handed double helix (S-DNA) which actually takes part in these form transitions. Two molecular models of this S form, in good agreement with X-ray measurements, are proposed. They present alternating C(2')-endo and C(3')-endo sugar puckering. Dihedral angles, sets of atomic co-ordinates and stereo views of the two S-DNA structures are given together with curves of calculated diffracted intensities.

Models, Molecular↗
PubMed1994

gamma-irradiation-induced grafting of poly (styrenesulfonate) to poly(tetrafluoroethylene) shielded microelectrodes.

A new method for the fabrication and polymer modification of microelectrodes is described. These electrodes are constructed by heat sealing the electroactive material in dual shrink/melt poly(tetrafluoroethylene) (PTFE) under vacuum. The PTFE shield may be activated to provide a support upon which polymers of interest may be grafted. gamma-Irradiation was used to graft polymerize styrene to the surface. The poly-(styrene) was subsequently sulfonated with chlorosulfonic acid to form poly(styrenesulfonate). Scanning electron microscopy and Raman microspectroscopy provide evidence that the poly-(styrenesulfonate) film has been formed and extends over the electrode material. Voltammetry indicates that hexaammine-ruthenium(III) cation is preconcentrated and stabilized via an association with the polymer film.

Cation Exchange Resins↗
PubMedDate not supplied

Water-soluble polyion complex associates of DNA and poly(ethylene glycol)-poly(L-lysine) block copolymer.

Complex formation of poly(ethylene glycol)-poly(L-lysine) (PEG-PLL) AB type block copolymer with salmon testes DNA or Col E1 plasmid DNA in aqueous milieu was studied. The PLL segment of PEG-PLL interacts with nucleic acid through an electrostatic force to form a water-soluble complex associate with a diameter of ca. 50 nm. PEG segments surrounding the core of the polyion complex prevented the complex from precipitation even under stoichiometric conditions, at which the unit ratio of L-lysine in PEG-PLL and phosphate in the DNA is equal. The profile of the thermal melting curve revealed a higher stabilization of DNA structure in PEG-PLL/DNA complexes compared to that in the complex made from DNA and PLL homopolymer with the same molecular weight as the PLL segment in PEG-PLL. This stabilizing effect on the DNA structure may be due to the compartmentalization of DNA into the microenvironment of PEG with low permittivity. The reversible nature of the PEG-PLL/DNA complex was further verified through the addition of polyanion [poly-(L-aspartic acid)]: Poly(L-aspartic acid) replaced DNA in the complex with PEG-PLL, resulting in the release of free DNA in the medium. Furthermore, the PEG-PLL/DNA complex showed high resistance against DNase I attack, suggesting DNA protection through the segregation into the core of the associate having PEG palisade.

Animals↗
PubMed1993

An A-form of poly(amino2dA-dT).poly(amino2dA-dT) induced by polyamines.

The effect of the naturally occurring polyamines spermidine and spermine on poly(amino2-dA-dT).poly(amino2dA-dT) conformation has been studied by UV, CD, and IR spectroscopies. It is shown that a conformational transition is induced in poly(amino2dA-dT).poly(amino2dA-dT) by micromolar concentrations of the polyamines (30 microM) in low-salt aqueous solution. The analysis of our results, in view of previously published studies on conformational properties of the amino polynucleotide, indicates the resulting conformer to be an A-form. Interestingly, the polyamine concentration at the midpoint of the transition is the same in both cases. This provides further evidence that the coordination of positively charged counterions to DNA is determined largely from the DNA structure, probably with an important role for the sequence, and less from the nature of the ions.

Circular Dichroism↗
PubMed1991

Inhibition of the B to Z transition in poly(dGdC).poly(dGdC) by covalent attachment of ethidium: kinetic studies.

The photoaffinity analogue ethidium monoazide was used to prepare samples of poly(dGdC).poly(dGdC) containing covalently attached ethidium. The effects of both noncovalently and covalently bound ethidium on the kinetics of the NaCl-induced B to Z transition in poly(dGdC).poly(dGdC) was examined using absorbance and fluorescence spectroscopy to monitor the reaction. Covalently and noncovalently attached ethidium were equal in the extent to which they reduce the rate of the B to Z transition. By using fluorescence to selectively monitor the fate of noncovalently bound ethidium over the course of the transition, we found that ethidium completely dissociates as the reaction proceeds, but at a rate that lags behind the conversion of the polymer to the Z form. These experiments provide evidence for the redistribution of noncovalently bound ethidium over the course of the B to Z transition, leading to the development of biphasic reaction kinetics. The observed kinetics suggest that the primary effect of both covalently and noncovalently bound ethidium is on the nucleation step of the B to Z transition. The reduction in the rate of the B to Z transition by noncovalently or covalently bound ethidium may be quantitatively explained as resulting from the reduced probability of finding a drug-free length of helix long enough for nucleation to occur. As necessary ancillary experiments, the defined length deoxyoligonucleotides (dGdC)4, (dGdC)5, and (dGdC)6 were synthesized and used in kinetic experiments designed to determine the nucleation length of the B to Z transition, which was found to be 6 bp. The activation energy of the B to Z transition was demonstrated to be independent of the amount of covalently bound ethidium and was found to be 21.2 +/- 1.1 kcal mol-1. Covalent attachment of ethidium was observed to increase the rate of the reverse Z to B transition, presumably by locking regions of the polymer into a right-handed conformation and thereby providing nucleation sites from which the Z to B conversion may propagate.

Affinity Labels↗
PubMed1992

Elsamicin A can convert the Z-form of poly[d(G-C)] and poly[(G-m5C)] back to B-form DNA.

The interaction of poly[(G-C)] and poly[d(G-m5C)] with the antitumor antibiotic elsamicin A, which binds to alternating guanine + cytosine tracts in DNA, has been studied under the B and Z conformations. Both the rate and the extent of the B-to-Z transition are diminished by the antibiotic, as inferred by spectroscopic methods under ionic conditions that otherwise favor the left-handed conformation of the polynucleotides. Moreover, elsamicin converts the Z-form DNA back to the B-form. The circular dichroism data indicate that elsamicin binds to poly[d(G-C)] and poly[d(G-m5C)] to form a right-handed bound elsamicin region(s). The transition can be followed by changes of the molar ellipticity at 250 nm, thus providing a convenient wavelength to monitor the Z-to-B conformational change of the polymers as elsamicin is added. The elsamicin A effect might be explained by a model in which the antibiotic binds preferently to a B-form DNA, playing a role as an allosteric effector on the equilibrium between the B and Z conformations, thus favoring the right-handed one.

Aminoglycosides↗
PubMed1984

Left-handed helical structure of poly[d(A-C)].poly[d(G-T)] studied by infrared spectroscopy.

Infrared spectroscopic studies demonstrate the ability of poly[d(A-C)].poly[d(G-T)] to adopt a Z-type conformation. The Z form of the unmodified polynucleotide is induced by Ni2+ counterions and not by Na+. The B----Z equilibrium is shifted at room temperature, in the presence of 1 Ni2+/nucleotide, by an increase in the concentration of poly[d(A-C)].poly[d(G-T)]. The importance of specific binding of Ni2+ ions on the N7 site of purines in the stabilization of the Z form is also discussed.

Cations↗
PubMed1985

Toroidal condensation of Z DNA and identification of an intermediate in the B to Z transition of poly(dG-m5dC) X poly(dG-m5dC).

Using a combination of spectroscopic techniques, quasi-elastic laser light scattering (QLS), and electron microscopy (EM), we have been able to show that the B to Z transition of poly(dG-m5dC) X poly(dG-m5dC) is accompanied by extensive condensation of the DNA in both low and high ionic strength buffers. At low concentrations of NaCl (2 mM Na+), an intermediate rodlike form, which exhibits a circular dichroism (CD) spectrum characteristic of an equimolar mixture of B and Z forms, is observed. This is produced by the orderly self-association of about four molecules of the polymer after prolonged incubation of a concentrated solution at 4 degrees C. On addition of 5 microM Co(NH3)63+, the CD spectrum of the intermediate changes to that of the Z form, which is visualized as a dense population of discrete toroids on an EM grid stained with uranyl acetate. On the other hand, addition of NaCl to a solution of poly(dG-m5dC) X poly(dG-m5dC) in the absence of any multivalent ion condenses the polymer to toroidal structures at the midpoint (0.75 M NaCl) of the B to Z transition. Further addition of NaCl unfolds these toroids to rodlike structures, which show characteristic Z-form CD spectra. These results show that Z DNA can take up a variety of tertiary structural forms and indicate that its inverted CD spectrum is due to its left-handed helical sense rather than to differential scattering artifacts.

Circular Dichroism↗
PubMed1986

Raman spectra of single crystals of r(GCG)d(CGC) and d(CCCCGGGG) as models for A DNA, their structure transitions in aqueous solution, and comparison with double-helical poly(dG).poly(dC).

The self-complementary oligonucleotides [r(CGC)d(CGC)]2 and [d(CCCCGGGG)]2 in single-crystal and solution forms have been investigated by Raman spectroscopy. Comparison of the Raman spectra with results of single-crystal X-ray diffraction and with data from polynucleotides permits the identification of a number of Raman frequencies diagnostic of the A-helix structure for GC sequences. The guanine ring frequency characteristic of C3'-endo pucker and anti base orientation is assigned at 668 +/- 2 cm-1 for both dG and rG residues of the DNA/RNA hybrid [r(GCG)d(CGC)]2. The A-helix backbone of crystalline [r(GCG)d(CGC)]2 is altered slightly in the aqueous structure, consistent with the conversion of at least two residues to the C2'-endo/anti conformation. For crystalline [d(CCCCGGGG)]2, the Raman and X-ray data indicate nucleosides of alternating 2'-endo-3'-endo pucker sandwiched between terminal and penultimate pairs of C3'-endo pucker. The A-A-B-A-B-A-A-A backbone of the crystalline octamer is converted completely to a B-DNA fragment in aqueous solution with Raman markers characteristic of C2'-endo/anti-G (682 +/- 2) and the B backbone (826 +/- 2 cm-1). In the case of poly(dG).poly(dC), considerable structural variability is detected. A 4% solution of the duplex is largely A DNA, but a 2% solution is predominantly B DNA. On the other hand, an oriented fiber drawn at 75% relative humidity reveals Raman markers characteristic of both A DNA and a modified B DNA, not unlike the [d-(CCCCGGGG)]2 crystal. A comparison of Raman and CD spectra of the aqueous [d(CCCCGGGG)]2 and poly(dG).poly(dC) structures suggests the need for caution in the interpretation of CD data from G clusters in DNA.

Crystallization↗
PubMed1986

Fluorescence-detected circular dichroism of ethidium bound to poly(dG-dC) and poly(dG-m5dC) under B- and Z-form conditions.

The equilibrium binding of ethidium to poly(dG-dC) and poly(dG-m5dC) under conditions favoring B and Z forms was investigated with fluorescence-detected circular dichroism (FDCD) and optical titration methods. FDCD spectra indicate a similar geometry for the intercalated ethidium under both B- and Z-form conditions, even at low levels of bound ethidium. The magnitude of the 310-330-nm FDCD band as a function of the bound drug to base pair ratio (r) indicates ethidium binds to poly(dG-dC) in 4.4 M NaCl and to poly(dG-m5dC) in 25 mM MgCl2 by clustering. Under these conditions, circular dichroism spectra indicate the polymer is largely Z form. Thus, it appears ethidium clusters into regions it has induced into a right-handed form. For all conditions studied, the FDCD spectra provided no evidence for a left-handed binding site. Under B-form conditions, binding is random.

Chemical Phenomena↗
PubMed1977

Interaction of DNA with poly(L-Lys-L-Ala-Gly) and poly(L-Lys-L-Ala-L-Pro). Circular dichroism and thermal denaturation studies.

Complexes of DNA with polypeptides composed of Lys, Ala, and Gly in both a sequential order, poly(L-lysine-L-alanine-glycine), and a statistical distribution, poly(L-lysine36-L-alanine28-glycine), were prepared using gradient dialysis. These polypeptide-DNA complexes were studied using ultraviolet absorption (UV) and circular dichroism (CD) to probe the conformation, binding, and melting behavior of DNA in the complex. Complexes with the sequential polypeptide showed no structural change in the DNA; however, the complexes with the random polypeptide yield CD spectra similar to phi DNA [Maniatis, T., Venable, Jr., J.S., and Lerman, L.S. (1974), J. Mol. Biol. 84, 37]. A second sequential polypeptide, poly(L-Lys-L-Ala-L-Pro)n, -DNA complex was also studied. It was found to exhibit pronounced structural changes as a function of ionic strength and poly-peptide-DNA ratio, more similar to the random sequence that the ordered sequence of the Lys, Ala, Gly polymer. Thus the importance of the composition and amino acid sequence in polypeptides which bind to DNA, even in such simple systems, is demonstrated. Evidence from thermal denaturation, employing simultaneous monitoring of CD and UV changes, supports a model in which specific polypeptides cause condensation of the DNA in the complex into an asymmetric tertiary structure. The relevance of these model systems to chromatin is discussed.

Alanine↗
PubMed1975

Infrared linear dichroism investigations of deoxyribonucleic acid complexes with poly(L-arginine) and poly(L-lysine).

Complexes between DNAs from various sources and poly(L-lysine) and poly(L-arginine) were studied by means of infrared linear dichroism. The measurements of dichroic ratios allowed us to determine the orientation of the phosphate group of DNA in the complexes with basic polypeptides. At high relative humidities (higher than 90%, B form), the bisector of the less than OPO in the complexes forms an angle with respect to the helical axis which has a value lower by about 4 degrees than in the corresponding DNA sample. This change of orientation of the phosphate group of DNA indicates a modification of the B form upon binding of polylysine or polyarginine. The structural transitions B leads to A and B leads to C measured as a function of relative humidities were not affected by formation of complexes with both basic polypeptides. Similar results were obtained for complexes prepared by direct mixing or by salt gradient dialysis. The presence of A and C forms was observed in complexes of DNA with poly(L-lysine) and poly(L-arginine) at lower relative humidity. Thus, the conformational flexibility of DNA in complexes with polylysine and polyarginine is not changed despite a substantial increase in the Tm (melting temperature). These results are considered as a model for the understanding of interactions between DNA and histones particularly of the binding of the N-terminal fragment, lysine or arginine rich.

Arginine↗
PubMed1997

Evidence for Hoogsteen GC base pairs in the proton-induced transition from right-handed to left-handed poly(dG-dC).poly(dG-dC).

The structure of double-helical poly(dG-dC).poly(dG-dC) is investigated at various pH values with Raman spectroscopy, absorption spectroscopy, and circular dichroism. A comparison is made between the B-form with Watson-Crick base pairing at 1 mM [Na+] and pH 7.2, the Z-form with Watson-Crick base pairing at 4 M [Na+] and pH 7.2, and a different structure at 1 mM [Na+] and pH 4.5 as well as at 150 mM [Na+] and pH 3.1. The CD spectrum of poly(dG-dC). poly(dG-dC) under the latter conditions does not show a negative band at 290 nm. The structure is a double-helical structure different from the B-form and the Z-form according to circular dichroism, Raman, and absorption spectroscopic studies. The Raman spectra evidence that the structure contains Hoogsteen base pairing. This can be accommodated in the double helix when the cytosine group is protonated and the sugar-guanine conformer has adopted a C2'-endo/syn conformation. It is shown that this antiparallel-stranded Hoogsteen base paired structure can be maintained under varying conditions, balancing the decrease in pH with an increased salt concentration. It is further concluded that the proton-induced transition from a Watson-Crick to a Hoogsteen base pair is aided by a decrease of [Na+] at pH 4.5 and occurs prior to a conversion from a right-handed helix to a left-handed helix.

Base Composition↗
PubMedDate not supplied

Enzymatic hydrolysis of bacterial poly(3-hydroxybutyrate-co-3-hydroxypropionate)s by poly(3-hydroxyalkanoate) depolymerase from Acidovorax Sp. TP4.

Enzymatic degradability has been investigated for a series of bacterial poly(3-hydroxybutyrate-co-3-hydroxypropionate)s (P(3HB-co-3HP)s) with 3-hydroxypropionate (3HP) unit contents from 11 to 86 mol % as well as poly(3-hydroxybutyrate) (P(3HB)) and chemosynthesized poly(3-hydroxypropionate) (P(3HP)). The behavior of degradation by two types of extracellular poly(3-hydroxyalkanoate) (PHA) depolymerases purified from Ralstonia pikettii T1 and Acidovorax Sp. TP4, defined respectively as PHA depolymerase types I and II according to the position of the lipase box in the catalytic domain, were compared in relation to the thermal properties and crystalline structures of the PHA samples elucidated by differential scanning calorimetry and wide-angle X-ray diffraction. The degradation products were characterized by high-performance liquid chromatography and one- (1D) and two-dimension (2D) (1)H NMR spectroscopy. It was found that the PHA depolymerase of Acidovorax Sp. TP4 showed degradation behavior different from that shown by depolymerase of R. pikettii T1. PHA depolymerase from Acidovorax Sp. TP4 degraded the P(3HB-co-3HP) films with lower crystallinity in higher rates than those with higher crystallinity, no matter what kinds of crystalline structures they formed. In contrast, PHA depolymerase from R. pikettii T1 degraded P(3HB-co-3HP) films forming P(3HB) crystalline structure in higher rates than those forming P(3HP)s. The increase in amorphous nature of the P(3HB-co-3HP) films with P(3HB)-homopolymer-like crystalline structure increases and then decreases the rate of degradation by depolymerase from R. pikettii T1. The 3-hydroxybutyrate (3HB) monomer was produced as a major product by the hydrolysis of P(3HB) film by PHA depolymerase from Acidovorax Sp. TP4. The P(3HB-co-3HP) films could be degraded into 3HB and 3-hydroxypropionate (3HP) monomer at last, indicating that the catalytic domain of the enzyme recognized at least two monomeric units as substrates. While the PHA depolymerase from R. pikettii T1 hydrolyzed P(3HB) film into 3HB dimer as a major product, and the catalytic domain recognized at least three monomeric units. The degradation behavior of P(3HB-co-3HP) films by the PHA depolymerase of Acidovorax Sp. TP4 could be distinguished from that by the depolymerase of R. pikettii T1.

Betaproteobacteria↗