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Q&A: Metropolitan Museum of Art's Julie Arslanoglu on Proteomics in Art History and Conservation

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By Adam Bonislawski

Name: Julie Arslanoglu
Position: Associate Research Scientist, Department of Scientific Research, Metropolitan Museum of Art
Background: Research Scientist, Getty Conservation Institute; Medicinal Chemist, National Cancer Institute; PhD, Organic Chemistry, Pennsylvania State University

Julie Arslanoglu is an associate research scientist in the department of scientific research at New York City's Metropolitan Museum of Art, where she collaborates with the museum's curators and conservators and conducts research on immunological and mass spectrometric techniques useful in the study of artwork.

Recently she received a three-year, $420,000 grant from the National Science Foundation to study techniques including ELISA and mass spectrometry for detecting, identifying, and localizing proteins in pieces of art with the goal of aiding conservation and authentication efforts.

This week she spoke to ProteoMonitor about her work at the museum, her plans for the NSF grant, and the general use of proteomics as a tool in art history and conservation.

The following is an edited version of the interview.


What are the main aims of the proteomics work you do at the museum?

The most important purpose is technical art history – to understand how a piece is made. One of the aspects of art is that often it's not just [composed of] one straightforward component. We see that in egg tempera where artists started to add oil as a transition to oil painting in Italy in the mid 1500s to 1600s. There are other cases where you might have the addition of gum binder to casein-based paint to create a particular effect. So to have the ability to take a single sample and screen it for three proteins and two gums and to be able to say that this paint is a mixture of, say, casein and gum – the idea of getting correct technical information about how something is made is important.

For us everything that we do starts with the question of, 'Why does this piece of art look the way that it does? Why is it flaking? Why is it behaving the way it does?' Getting that kind of information about what the art is made of to help the conservators make correct conservation decisions; to help conservators and curators make decisions on what's the best display or storage for this artwork. 'Should it travel? How do we store it?' That's the most important thing we do.

What sort of techniques do you use in your work?

While we have FT-IR and GC-MS analysis techniques for protein and gum identification, at the Met we decided initially to investigate an immunological approach. This approach has been done in the past, but there's been a resurgence of interest, mainly because the specificity of the antibodies available commercially has increased in our area of interest, and also the cost has come down. It's a colorimetric assay, and it's something that you can do in a museum laboratory.

At the same time, there's been a surge of people working in the proteomics field using either MALDI-TOF or LC-ESI-QTOF to look at peptides in art materials to identify the proteins that are there. That's definitely a very strong area of research that's going on. There are several labs doing that throughout the world. One lab in particular is at Harvard, the Straus Center [for Conservation and Technical Studies], where Dan Kirby is doing research trying to make this [MALDI-TOF] approach more of a benchtop approach. He and I are working together because we saw that there was this complementary nature between the peptides that will be stable that you can identify using proteomics, and how you could go about exploiting that information to increase the specificity and reliability and reproducibility of your ELISA assays.

When did people begin using proteomics approaches to study art?

With immunological techniques the earliest attempts were in the 70s, and in archaeological work they've been very successful. So that was something that we as a group of scientists started to look at again. The [mass spec-based] proteomics came into it when around 2002 laboratories that did proteomics got involved in the cultural heritage field. They already have access to these large databases of amino acid sequences and peptide sequences, and they're able to do either the peptide analysis using a mass fingerprinting technique or even sequencing using some sort of LC-MS technique.

So as that information becomes more concrete and more accessible to us in the art research area, we're looking to try to bring it in at a museum level.

So you're taking the research these larger proteomics labs have done and applying it to your work at the museum?

Exactly. They are people with real expertise in this who are doing the kind of basic research that you need to have. You need a good instrument and good people and a lot of time, and usually we don't have the time or the money or the instrumentation, so this is very useful to us.

Who are the labs that are doing this sort of basic research?

Most of them are academic. Usually what happens – in Europe, and we're trying to do more of it here – is that there's a cultural application and somebody in the cultural field makes a contact with somebody in the academic field, or even, if you're lucky, industry, and there's enough interest to do a small project, and if there's enough success it develops into a larger project. That's what you hope for, to have someone who has the time, the instrumentation, the money, and the personnel to be able to do the basic type [of] research that we can then incorporate into what we do.
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You recently received a National Science Foundation grant for your protein research. What sort of research do you plan to do with that award?

I do a small amount of basic research on a very low level on a daily basis, but with this grant I'll be able to hire a post-doc. I have the commitment and the finances now for three years to do more applied research, and for that I have access to laboratories at Columbia University through my collaborator John Loike [the co-director for Graduate Studies in the Department of Physiology and Cellular Biophysics at Columbia University College of Physicians and Surgeons].

I want to address a couple of issues having to do with protein identification. I definitely would like to use immunological approaches but we're not going to limit ourselves to those. So one of the aspects is to create authentic protein binders from original sources following original recipes and then mix them with different pigments and do some artificial aging so that we have a good set of research materials – so that we have knowns, shall we say.

Then [we'll look] to the work Dan [Kirby] is doing trying to identify the peptides that are the most stable that we can use to increase the sensitivity and reliability of our ELISAs. There are all sorts of issues that go along with that because ELISA is sensitive to pigment interference, and also trying to get the protein out of the samples is an issue. That's the general thrust of the research.

However, because we're going to be identifying peptides that will be targets for us, one of the pilot studies I'd like to do is some aptamer research to see if that might be a more sensitive and accurate method than antibodies. One of the drawbacks of the ELISA technique is that because we're relying on commercial sources, if the company decides to change its purification technique, for example, suddenly an antibody that's been working great will no longer work at all. So that's a drawback because then basically you have to reinvent a new method.

Another aspect of our research is the localization of proteins and gums in cross sections [of pieces]. We're using [surface-enhanced-Raman-labeled] nanotagging. What we're trying to do now is multiplexing so you can identify more than one protein in a cross section in one experiment using unique nanotags for each protein.

What types of proteins are you typically interested in?

There are basically three main animal sources that we're interested in. One is collagen-based. These are paints or adhesives that were made from animal skins, hooves, tendons, but also fish bladders. Then there are paints or adhesives made from milk – so casein. And then there are paints and adhesives made from eggs. There you have a choice – you can have a whole egg, an egg yolk, or an egg white.

The other aspect of the [MALDI-TOF-based] proteomics work is that there's a lot of species specificity work being done in that area. For example, they can say [if a sample contains] bovine casein versus goat versus sheep versus camel. We hope we can capitalize on that and bring it to a more basic benchtop immunological method.

Do you work closely with art historians and curators at the museum?

Absolutely. My lab space is located in the paintings conservation department while other labs and offices are adjacent to or in paper, textile, or objects conservation. Our offices, our labs, are right in the middle of the conservation departments. So we're accessible to the conservators and the curators who come with questions, but also we're part of the whole workflow. We see what's coming in, and if we have questions we can go talk to the conservators and curators. So it's really beneficial to have that kind of open dialogue.

Are you involved much in the process of authenticating pieces of art?

Sometimes. At the Met anything that's brought up for consideration is usually well provenanced and it's rarely that kind of a question. There are other places where there's a need for a more rigorous authentication process where you want to examine the pigments or the binding media to make sure it's right. On occasion there will be a piece – and I'm thinking more of objects than of paintings – that might have an early restoration or conservation. So you might have two parts of the same object – one of which is clearly more recent than the other – and it's not so much an issue of authentication as trying to understand what the construct of the piece is and how it's changed throughout history.

What's an example of a recent project you've worked on?

We have a 13th-century Italian polychrome statue from the Cloisters, and it has some gilding, some metal leaf that's applied directly to the ground layers. So the question was, 'What's the adhesive that holds down the metal leaf?' Because the ground layer, the preparatory layer on top of the wood, is made of a collagen binder, doing that analysis by GC-MS probably won't give you a clear answer because there's so much collagen that picking up any other protein component, unless it's in a really high concentration, is going to be very difficult.

So we did an ELISA, taking a scraping as a sample just below the metal leaf and then taking another scraping below that one. We found that the scraping just below the metal leaf contained both albumin and collagen, and that the scraping further down contained almost exclusively collagen. So from that we could deduce that the adhesive for applying the metal leaf was egg.

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