JPH02214726A - Polypeptide thin film and production of material carrying same - Google Patents

Abstract

PURPOSE:To obtain the title material having peptide linkage-carrying thin film of good biocompatibility by polymerizing monomolecular film or build-up film containing a specific amphipatic compound having in one molecule hydrophobic domain and hydrophilic one carrying amino acid ester structure followed by carrying. CONSTITUTION:A monomolecular film is formed on gas/liquid interface. This film contains an amphipatic compound having in one molecule hydrophobic domain and hydrophilic one carrying amino acid ester structure with the pKa of the conjugate acid for the elimination group in this ester being <=14. This monomolecular film is then polymerized on the interface followed by transferring the resultant polymer in the form of either monomolecular or build-up film onto a substrate, and further polymerization is made, thus obtaining the objective material carrying a polypeptide thin film.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing a thin film composed of a molecular assembly and a material supporting the same, and in particular a thin film comprising a peptide bond that is excellent in biocompatibility. The present invention relates to a method for producing a thin film of an optically active amino acid polymer and a material supporting the thin film.

(Background technology) A monolayer film with molecular alignment (onolayer) and a cumulative film (g+onolayer) formed by laminating multiple monolayers
Molecular assemblies such as yers=s+ultilayer) take advantage of their ultra-thinness and compactness to be used as materials for electronic devices, surface protection materials, and sensors that utilize selective permeability of gas molecules and ions. It is expected to have a wide range of applications as functional thin films and permeation control membranes for material delivery.

The Langmuir-Prodgett method is generally known as a method for accumulating a monomolecular film of amphiphilic molecules formed at the gas-liquid interface on a support.
The use of IIl as an organic ultra-thin film has expanded in recent years [see Solid State Physics 17 (12) 45 (1982), etc.].

Molecular assemblies including LB films are based on molecular orientation and ultra-thinness (
Although they exhibit a variety of functionalities, they also have the disadvantage that they are physically delicate, so the membrane structure is easily destroyed, and some compounds have many structural defects in the membrane, making it difficult to achieve high density.

Physically strengthening the membrane structure of these molecular assemblies and providing a uniform, high-density membrane is a challenge required for all purposes.

One of the effective means for physically reinforcing the membrane structure of molecular assemblies is crosslinking or polymerization of molecules.

Regarding the polymerization of LB films, conventional polymerizable compounds and polymerization modes are described by H. Bader et al., Advances in P.
olymerSCIeIIle6+ Vol. 64, p. 1 (1985) and R, B"IIa ch l et al.
Macromol, Chew, 5upp1. + Summarized in Volume 6, page 245 (1984).

Research on polymerizable amphiphilic compounds became active in 19
This started in the 1980s, and initially a method was widely adopted in which vinyl, diene, and diacetylene-based unsaturated compounds were used as polymerizable compounds, and polymerization was performed using radiation such as ultraviolet rays (UV) or T-rays. However, although polymerization by these methods yields robust polymers, it is difficult to maintain the order of the molecular arrangement after the unsaturated bonds are cleaved.

By Le Aschewsky and H. Ringsdorb,
Macromolecule+ Volume 21, page 1936 (
(1988), the film orientation is greatly influenced by the length of the alkyl chain and the type of terminal parent group;
Polymerizable compounds with good orderliness are limited to a small number.

A. Laschewsky et al. also J. Am. Ches.
, Soc, , Volume 109, 788v1. (198
7) disclosed the necessity for the polymerizable group to be supported via a spacer group in order to maintain order in amphiphilic compounds having various unsaturated bonds useful for radiation polymerization, etc. are doing. Furthermore, JP-A-57-1
No. 59506 discloses an example of using a polymerized film of a monomolecular film and a cumulative film of an unsaturated compound (surfactant) by radiation polymerization as an ultrafiltration membrane.

Conventional techniques for polymerizing compounds having these unsaturated bonds by radiation have the following disadvantages. That is, first, disorder of the arrangement structure or disordered aggregation/precipitation of molecules is likely to occur due to polymerization, and special molecular design such as insertion of a spacer group is required to avoid this. A second problem is that irradiation with ultraviolet rays or T-rays causes decomposition or denaturation of various additive substances that often coexist with polymerizable amphiphilic molecules. Thirdly, membranes obtained by this type of polymerization usually have extremely poor biocompatibility and have a high resistance to permeability of drugs, etc.
The application to biological tissues as such is limited.

Therefore, as a polymerization method that does not use radiation, for example, a method of forming disulfide bonds by oxidative polymerization of dithiol is proposed, for example, in J.
, p. 4419 (1987) or the method of radically polymerizing the above-mentioned compound having an unsaturated bond in the presence of an initiator is useful.

However, these methods require an initiator during polymerization, which requires a step to remove it from the membrane system after the polymerization is complete, and there is also the problem of the effect of initiators, including redox agents, on coexisting substances. Become.

J, Am describes a method in which a molecular membrane of an amino acid derivative is subjected to condensation polymerization in the coexistence of a carbodiimide to improve the polymerization form and biocompatibility.

Chew, Soc, + No. 108 @, page 487 (19
(1986), but this method also poses a problem of residual condensing agents and by-products and requires control of the efficiency of the condensation reaction, making it difficult to handle.

[Ll that the invention tries to solve! Therefore, the purpose of the present invention is to solve the problems of the above-mentioned conventional methods, and firstly, to produce a thin polymer film with good molecular alignment and a material supporting it without using radiation or a polymerization initiator. Second, the purpose is to provide a method for producing a polymerized thin film in which polymerization proceeds spontaneously and in high yield through self-polymerization, and a material supporting the same. The purpose of this invention is to provide a polymerizable thin film that is also excellent in biocompatibility.

(Means for Solving the Problems) An object of the present invention is to provide a parent xylem having a parent xylem having a hydrophobic part and an amino acid ester structure in one molecule, and having a pKa of the conjugate acid of the leaving group of the ester being 14 or less. A polypeptide thin film obtained by polymerizing a monomolecular film containing a medium compound or a cumulative film thereof, and a polypeptide having a hydrophobic part and a hydrophilic part having an amino acid ester structure in one molecule, and the conjugate acid of the leaving group of the ester. A monomolecular film containing an amphipathic compound having a pKa of 14 or less is formed at the gas-liquid interface, polymerized at the interface, and then transferred onto a support, or the monomolecular film is transferred onto a support. This was achieved by a method for producing a material carrying a polypeptide thin film, which is characterized in that it is transferred as a monomolecular film or a cumulative film and then polymerized.

The polymerized monolayer or cumulative film of the present invention is an ultra-thin film supported on a support by a monolayer coating method including the Lanqs+uir-Blodgett method, and the main chain of polymerization is composed of a polypeptide, that is, a chain of amide bonds of amino acids. It is characterized by being That is, the polymer membrane of the present invention is obtained by condensation polymerization of an amphipathic amino acid derivative having a reactive, that is, electrophilic, ester group through the following reaction to form an amide bond skeleton.

1? R Here, n represents an integer of 2 or more. R and R'X will be described later.

The method for forming the polymerized thin film of the present invention will be explained.

For forming a polymerized thin film, either of two types of polymerization, polymerization at the gas-liquid interface and polymerization on a support, can be used.

In order to perform polymerization at the gas-liquid interface, a monolayer of the amphiphilic amino acid ester derivative monomer of the present invention (formula (I) above) is placed in the aqueous phase (subphas) of a trough for monolayer production.
e) The aqueous phase can be prepared by developing it with an appropriate organic solvent and leaving it on the water surface for an appropriate period of time, preferably 30 minutes to several hours.The aqueous phase is pure water or a salt solution such as a buffer. can be used, and the pH is preferably controlled within the range of 5 to 9 depending on the equilibrium constant of ester decomposition of the monomer used.

The temperature of the aqueous phase is preferably in the range from room temperature to 60°C, and a high temperature is selected to promote the reaction.The surface pressure of the monomolecular film during the reaction is preferably maintained at 5 to 40 dyne/cm; It is more preferable to keep it at ~25 dyne/c:m. The surface pressure is usually controlled at a constant value, but may be increased or decreased as the reaction progresses. After the reaction is completed, the polymer film on the water surface is
- By sequentially transferring one layer or multiple layers onto a hydrophilic or hydrophobic support by a method such as the Blodgett method (vertical dipping method) or horizontal deposition method, a polymerized monomolecular film is formed into a polymerized cumulative film. .

The second method is to form a monomolecular film of the amphipathic amino acid ester derivative monomer (1) on the water surface, transfer it onto a support by the method described above, and then form a cumulative film on this support. This is a method of allowing polymerization to proceed by leaving it to stand. In order to accumulate a monolayer on the support prior to reaction in this method, it is necessary to maintain the aqueous phase at conditions that inhibit the polymerization reaction, such as low pH and low temperature conditions.

The monomers accumulated on the support are subjected to conditions that promote polymerization, such as heating and alkaline gas (such as NH, etc.).
It can be polymerized by exposure to water or immersion in an alkaline aqueous solution.

Of these two polymerization methods, the former method, polymerization on the gas-liquid interface, is preferred in terms of reaction tolerance. However, this is not necessarily the case in terms of reaction efficiency.
It can be used depending on the stability of the monomer used.

The amphipathic amino acid ester used in the present invention is represented by the following general formula (I).

(I)0 HEN-CHCXR' In the formula, R is a long-chain alkyl group (preferably 12 to 2 carbon atoms
XR+ is a leaving group whose conjugate acid has a pKa of 14 or less. X represents 10--3- or -N (R'')- (R1 is a hydrogen atom, an alkyl group, an aryl group, Rz may be linked with R1 to form a ring, this ring may further be may contain a hetero atom such as nitrogen, and may have an unsaturated bond), X is preferably 10-, RI
For example, aryl groups (including substituted aryl groups)
For example, phenyl, naphthyl, substituents such as nitro group, halogen atom), haloalkyl group (e.g. monochloromethyl, dichloromethyl, trichloromethyl), acylamino group (e.g. N-methylacetylamino group, N
-Methylbenzoylamino5), -N-CR" (
R' ) (where R1 and R4 are hydrogen atoms, alkyl groups,
Examples of the alkyl group and aryl group (including those having a substituent), alkenyl group, and alkynyl group, which represent an aryl group. Among these, aryl groups containing substituted aryl groups are preferred.

The linear alkyl group for R preferably has 16 to 20 carbon atoms, and when the alkyl group is bonded to an amino acid residue via a linking group, the linking group is -NHCO--
NHCOO- -NHCON)I--NHCO-3--0--3--C
Preferably, oo--0PO3e* or a combination of these and an alkyl group is preferred.

Next, preferred specific examples of the amino acid ester (monomer) of the present invention will be listed, but the invention is not limited thereto.

N.H.

■-4 X=C1, Br, I or! -10 X proverb Cj! , Br+ 1 or F US HJ CC-OR' Below, synthesis examples when R= Cls Hs t (n) are given and compound 1' (R-Ctm
Hzv(n)) is T, Folda, L, Gros
, H. Ringodorf Makromol.

N11° CI! .

■-2O H1 C+Jst CHC0-CH earthquake-CI = CHzH
I CtmHzv CHC0-CHg c=cu The above amino acid ester can be synthesized by the following synthetic route.

Chew, Rapid Commun, 3
It was synthesized according to the method described in Vol. 167 (1982). ■, p of compound 1' is 94° to 98°C, rR spectrum (Nujol) of this compound is 1760C
I-' (ester carbonyl) 3200 cm-',
1640 cm-', 1550 CII (ammonium salt).

35 g (0.093 mol) of Compound 1' was dissolved in 200 d of tetrahydrofuran, 21 g (0.19 mol) of EhN was added, and the mixture was stirred at room temperature for 10 minutes.

243 g (0.14 mol) of di-tart-butyl carbonate (Tokyo Kasei product) was added thereto, and the mixture was stirred at room temperature for 10 hours. After completion of the reaction, tetrahydrofuran was distilled off under reduced pressure, and ethyl acetate 20 (ld) was added. water 2
00d was added and extracted. This was repeated twice, and the resulting organic layer was washed once with saturated NaCl water, NaSO,
Dry at. White crystals were obtained by distilling off the organic solvent under reduced pressure. When this is recrystallized with ethanol/hexane system, compound 2' [R=l+J3 in compound 2? (n))
41g of was obtained.

m, p, 85-886 I R3350cm-' (NH) (Nujol) 1760cm-' (ester) 1
720 cm-' (Ureta 7) Compound 2' log (0,024 mol) was dissolved in 200 d of a 2:1 mixed solution of tetrahydrofuran and CH3OH.
10 m of an aqueous solution of 2 g (0.05 mol) of sodium hydroxide was added dropwise into the solution. The mixture was stirred at room temperature for 12 hours and acidified to around pH-4 with dilute hydrochloric acid while cooling in a water bath. 200 d of water was added, and the mixture was extracted three times with 100 d of ethyl acetate, and the organic layer was washed with water and dried over NatSO4. When the aqueous solvent was distilled off under reduced pressure, crystals were obtained. Recrystallization from ethyl acetate/hexane yielded 7.2 g of compound 3' (R=C+5Hit(n) in compound 3).

11, G1. 121-1241 1 R3400cm-' (NH) (Nujol) 2800-2600cm-' (Carboxylic acid OF+) 1720cm-' (Carboxylic acid carbonyl) 1700Cm-' (Urethane) Activity with long chain alkyl described in this patent The esters were synthesized by using Compound 1 with various alcohols and a condensing agent called dicyclohexylcarbodiimide.

The case where phenol is used is described below as a representative example.

Compound 3' 1.8 g (0,0042 mol) and phenol 0.4 g (0,0043 mol) were dissolved in 100 d of ethyl acetate, and 0.95 g (0,0046 mol) of dicyclohexylcarbodiimide (Tokyo Kasei Products) was dissolved. )
added. After stirring at room temperature for 12 hours, the mixture was cooled in a water bath and the precipitate was filtered off. The mother liquor was condensed and the residue was purified by silica gel column chromatography (eluent: hexane: ethyl acetate: 8:1) to yield compound 4a (
Ugly, p, 125-129゜I R3360CII-' (NH) (NuJol) 1780 C1-' (Ester)
1695 cm-' (urethane) 1600 cm-' (-substituted benzene) Compound 4a Ig was dissolved in 10 ae of anhydrous chloroform and cooled to 0°C in a water bath. 51 d of CFsCOz)I was added thereto and stirred at 0°C for 30 minutes. The solvent was distilled off under reduced pressure, and the obtained white crystals were dissolved again in chloroform 20id, and the chloroform layer was washed twice with 5% NaHCO and an aqueous solution of lO-. After washing the chloroform layer with water, Naz
After drying over SOa, the solvent was distilled off under reduced pressure using a water bath to obtain 0.7 g of the target compound 1-3 as white crystals.

Since this compound decomposes when left at room temperature, the structure was confirmed by IR spectrum (as shown in the 4th section) and then subjected to the membrane manufacturing process without purification.

Other compounds were synthesized using similar methods.

Since the compound is unstable, the cocoon of its intermediates 4b to 4e, p,
shows.

In the present invention, various organic resin materials and inorganic materials having hydrophilic or hydrophobic surfaces are used for the support (substrate) covering the monomolecular film or the cumulative film.

These may be flat or may have a porous or fibrous three-dimensional network structure.

Flat materials include various metals and other conductive materials, glassy inorganic materials (glass, quartz, etc.), other inorganic insulators, various inorganic and organic crystals, and inorganic semiconductors (S n Ox
, I nz Os , Z n Os T iOx, WO
, GaAs, SL, etc.), organic semiconductors, organic conductors, organic polymers, and composite materials of the above materials. The material may be a bridge or other sensor (such as a field effect transducer) connected to an external electrical circuit.

Porous materials are mainly useful as supports when used as permeable membranes or filters, and include, for example, organic and inorganic microporous filter cellulose resin films and various other porous polymer films.

The developing solvent for monolayers used in the present invention includes commonly used volatile non-polar organic solvents such as chloroform, dichloromethane, benzene, toluene, and ether, as well as mixtures of these with polar hydrophilic solvents such as alcohol and water. is also used.

Various deposition methods can be used to coat the monolayer on the water surface onto the surface of a substrate or support, including the LB method. Regarding the LB method, which is a vertical deposition method, see, for example, the Journal of the American Chemical Society 4.
(J, A, Chem, Soc,) Volume 57, 1007
Page (1935), Gaines, G.L., Ga1ns, J.
``Insoluble Mol-Yers at Liquid-Gas Interface'' by R)
Monolayers at Liquid-G
asInter4aces) J, (Intersc
New York (1966), or by Kiyonari Fukuda, Materials Technology, Vol. 4, p. 261 (19
1986), etc.

Other coating methods include horizontal deposition method and rotational deposition method (
For example, JP-A-60-189929, JP-A No. 61-4239
Various methods such as No. 4) are applied. A cumulative film is obtained by repeatedly performing the operation of coating a substrate with a monomolecular film.

For efficient accumulation, the improved horizontal adhesion method described in Japanese Patent Application No. 63-54680 and Japanese Patent Application Laid-Open No. 60-20924 are recommended.
It is also possible to use the continuous cumulative method described in No. 5 and the like.

Examples of the present invention are shown below, but the embodiments of the present invention are not limited thereto.

[Example 1] Exemplary compound 1-1 as an amphipathic amino acid phenyl ester was dissolved in dichloromethane at a concentration of 1 mM to prepare a developing solution. A monomolecular film was prepared by spreading this solution on an aqueous phase of a 10-''M phosphate buffer solution at pH 7.4 using a Langmier film balance. Immediately after the film was formed, this monomolecular film was formed using a belt-driven barrier. The monomolecular film was compressed at a speed of 101:7 minutes, and the surface pressure-molecular occupied area (π-A) characteristics at 20°C were measured, and the results of the first A were obtained. Better than the π-A characteristics. The monomolecular film was left at room temperature for about 2 hours under a constant surface pressure of 15 dyne/1 on this buffer aqueous phase to allow polymerization to proceed. As a result of measuring the π-A characteristics again after leaving it, the characteristics shown in B in Figure 1 were obtained.Due to zero polymerization, the molecules became denser and the membrane contracted, and the bursting pressure also increased and the membrane was strengthened. That is clear.

This polymer film was compressed to 30 dyne/cm, and then 40 M was deposited on a gold-deposited glass substrate by a horizontal deposition method.

As a result of measuring the Fourier transform infrared absorption spectrum of the cumulative film on the entire surface by reflection absorption method, the characteristic absorption band of phenyl ester disappeared, and an absorption band indicating the formation of amide bond appeared at 1650 to 1700 cm. It was shown that a polypeptide was produced by polymerization. Furthermore, when we compared the spectra obtained by measuring a sample accumulated on a silicon substrate using the transmission method, we found that in the reflection method, the absorption of C-H stretching of long-chain alkyl groups was more pronounced than the absorption of C-0 stretching of amide. It was found that the long-chain alkyl axes were oriented perpendicular to the substrate surface, confirming that the molecular alignment was maintained.

[Example 2] A developing solution was prepared according to Example 1 using Exemplary Compound ■-3 as the amino acid phenyl ester, and the π-A characteristics were measured at 20°C. The characteristics of C in Figure 2 for the monomer before polymerization were measured. was gotten.

This monomolecular film was heated at 35°C for about 80 minutes with 25 dyne/
Under a constant surface pressure of cm p)! 7.4 was allowed to stand on the water surface for polymerization, and after the polymerization, the π-A characteristics were measured again. As a result, the characteristics shown in Figure 2 were obtained, and it is clear that the membrane contracted and strengthened due to polymerization.

To measure the polymerization rate, the monolayer was stained with S after an arbitrary period of time.
About 40 layers are accumulated on a t-wafer substrate by horizontal deposition method,
The infrared absorption spectrum of the accumulated film was measured by the transmission method,
The rate of decrease in the characteristic absorption (~1750 CI-') of phenyl ester was investigated. As a result, after 10 minutes of reaction, approximately 50
%, it was shown that after 60 minutes of reaction, about 90% of the ester disappeared to form an amide bond.

[Comparative example]

For comparison, a monomolecular film formed on a water surface was polymerized in the same manner as in Example 1 using the following amphipathic amino acid methyl ester monomer.

A buffer aqueous solution with pH 7.4 was used as the aqueous phase, and the temperature was 20
Measurements were carried out at two points: °C and 35 °C. The π-A characteristics of the above monomer at 20°C are exemplary compounds! It showed similar characteristics to -3, and the bursting pressure was around 35 dyne/cm. This monomolecular film was maintained at a constant surface pressure of 156 yne/cm on each of the aqueous phases at 20°C and 35°C for about 2 hours, but there was almost no change in the area of the film. As in Example 2, 40 layers of these films were accumulated on a Si wafer and the FT-IR spectra were measured.

As a result, the IR spectrum of the cumulative film in any temperature system showed strong ester absorption (~1730C11-'
) remained, and almost no amide bond formation was observed. Furthermore, after leaving this monomolecular film at room temperature for about 20 hours on an aqueous phase with a pH of 9, which further increases the ester activity, under a surface pressure of 15 dyne/cm, the cumulative absorption was measured in the same manner. A weak, broad absorption was observed in ', which was thought to be due to the formation of an amide bond, but the sharp absorption of the ester group still remained, and the reaction did not come to an end. It is thought that the polymerization rate of this alkyl ester derivative is at least two orders of magnitude lower than that of the aryl ester derivative of the present invention.

[Example 3] A polymer film of the compound used in Example 1 was deposited in 4 to 16 layers on the surface of a grady carbon electrode under 30 dyne/cm in the same manner as in Example 1, and used for electrochemical measurement. Based on this, we conducted a permeability evaluation.

Selecting a metal ion as a substrate for permeation, Ks Fe
(CN) 61mM, KNo, 10mM by immersing the above polymer membrane-coated Grazi-carbon electrode in a neutral electrolyte solution consisting of 61mM KNo, 10mM KNo.
The redox current of "Fe" was measured by cyclic portammetry. The electrode potential was controlled relative to a saturated calomel electrode, and the electrolysis was carried out under a Nl gas barge. The portamogram was obtained by performing approximately 30 repeated potential scans. Portammetry was performed on the polymerized film of the present invention, and also on a monomolecular film of the monomer before polymerization that was accumulated on the electrode immediately after spreading, and the two were compared.

Figures 3A and 3B show the results.

The current value peak shown in the cyclic portammogram (
In other words, the amount of Fe'' permeated through the membrane (corresponding to the amount of Fe'' permeated through the membrane) is noticeable in the monomer cumulative membrane system (Figure 3A), starting from about 8 layers (curve 2), and decreases to about 16 layers (curve 3) due to the accumulation of 16 layers (curve 3). 1/
However, in the polymerized membrane, i.e., polypeptide membrane system (Fig. 3B), the current decrease of about 115 already occurs due to the accumulation of 4 layers (curve 5), and in the case of 8 layers (curve 6), the current decreases to 2 digits. decreased.

That is, it is clear that as a result of polymerization, a significant permeation suppressing effect was obtained. When a similar portamogram was measured for the methyl ester used in the comparative example, the current suppressing effect was small, decreasing by about 1/2 to 1/3 in the case of 8 layers cumulatively.

[Brief explanation of the drawing]

Figure 1 A shows a monomolecular film of the monomer of Exemplary Compound 1, and B shows the isothermal characteristics of the surface pressure of the monomolecular film after polymerization (2 hours at room temperature) and the area occupied by molecules (π - A) at 20°C. . FIG. 2 C shows a monomolecular film of the monomer of Exemplified Compound 3, and D shows the π-A isothermal characteristics of the monomolecular film after polymerization (2 hours at room temperature) at 20°C. FIG. 3A is a portammogram of a cumulative film of the monomer of exemplified compound 1, where 1 is no film, 2 is a film consisting of 8 layers, and 3 is a film consisting of 16 layers. B is a portammogram of a polymerized cumulative film of exemplified compound 1, 4 is the same as 1 without a film;) 5 is a film consisting of 4 layers, and 6 is a film consisting of 8 layers. FIG. 4 is a chart showing the infrared absorption spectrum of Compound 1-3.

Claims (2)

[Claims] (1) A monomolecular film or a cumulative film thereof containing an amphipathic compound that has a hydrophobic part and a hydrophilic part with an amino acid ester structure in one molecule, and the pKa of the conjugate acid of the leaving group of the ester is 14 or less. A polypeptide thin film obtained by polymerization. (2) A monomolecular film containing an amphipathic compound that has a hydrophobic part and a hydrophilic part with an amino acid ester structure in one molecule, and the pKa of the conjugate acid of the leaving group of the ester is 14 or less, is attached to the gas-liquid interface. The method is characterized in that the monomolecular film is formed on a substrate, polymerized at the interface, and then transferred onto a support, or the monomolecular film is transferred onto a support as a monomolecular film or a cumulative film, and then polymerized. A method for producing a material supporting a peptide thin film.