Zeiss IM35 microscope fluorescent cubes – suggestions for microscopy at LRO

ADVICE FROM CHATGPT:

The Zeiss IM35 was originally designed to accept interchangeable fluorescence reflector/filter blocks, and I’ve found period evidence for several combinations actually used with the IM35.

The most useful original-style options were:

There is particularly good evidence for the first two: an IM35 fluorescence system currently documented with its original-style tray contains BP 450–490 / FT510 / LP520 and BP365 / FT395 / LP397 cubes.

The BP546 / FT580 / LP590 combination is also specifically documented in scientific work performed using a Zeiss IM35. Another IM35 application used BP510–560 / FT580 / LP590 for rhodamine-labelled material.

For your IM35 and the dyes you’re interested in

The one I would particularly look for is:

Zeiss BP 450–490 / FT 510 / LP 520

That’s the classic fluorescein/FITC cube and is the right general filter combination for fluorescein diacetate (FDA) after intracellular conversion to fluorescein. In fact, an IM35 study explicitly describes the fluorescein combination as BP450–490 / FT510 / LP520.

Interestingly, later Zeiss nomenclature identifies essentially this combination as Filter Set 09; an IM35 study also specifically reports using Zeiss 09 (BP450–490/LP520) for calcein, EGFP/EYFP and Lucifer Yellow.

One important caution when buying second-hand: don’t assume a modern Zeiss P&C fluorescence cube will physically fit the IM35. Later Zeiss P&C reflector modules are a different mounting system, and sellers explicitly warn that the newer P&C and older screw-mounted modules are not interchangeable.

Looking for original 1970s/1980s Zeiss IM35 catalogue/manual and identify every fluorescence filter block Zeiss actually offered for it, including the original Zeiss part numbers:

Yes. I dug further, and we can now identify the classic Zeiss filter combinations that are particularly relevant to the IM35 with much more confidence.

One complication is that Zeiss reused/updated filter-set numbering over the years, so I would search for the three actual filter specifications (BP / FT / LP) rather than relying solely on a number.

Fluorescence Zeiss combination Typical fluorochromes Priority for your IM35:

UV / DAPI BP 365 / FT 395 / LP 397 DAPI, Hoechst, UV fluorescence ★★★

Blue / FITC BP 450–490 / FT 510 / LP 515 or LP 520 Fluorescein, FDA, FITC ★★★★★

Blue-green bandpass BP 450–490 / FT 510 / BP 515–565 FITC-type fluorescence with reduced background ★★★★

Rhodamine BP 546 / FT 580 / LP 590 Rhodamine, TRITC ★★★★★

Violet/blue BP 436 / FT 460 / LP 470 blue-excited fluorophores ★★★

The particularly useful confirmation is an actual IM35 fluorescence microscope equipped with two original-style cubes: one contains BP450–490 / FT510 / LP520 and the other BP365 / FT395 / LP397. 

The three I’d collect:

For an IM35 today, I’d aim eventually to have these three:

1. FITC/fluorescein — BP450–490 / FT510 / LP520

This is the important one for your fluorescein diacetate (FDA) work. The blue excitation passes roughly 450–490 nm onto the specimen; FT510 reflects the excitation while transmitting the fluorescence; LP520 then lets the green fluorescence reach your eye/camera.

Modern Zeiss documentation gives essentially the same FITC family of combinations, including BP450–490 / FT510 / LP515. 

2. Rhodamine — BP546 / FT580 / LP590

This gives you a second, very useful colour channel. More importantly, I’ve found a 1988 paper where researchers specifically used a Zeiss IM35 with a Zeiss rhodamine filter, giving excitation at 554 nm and emission >580 nm. 

The standard Zeiss rhodamine set subsequently documented by Zeiss is BP546 / FT580 / LP590. 

3. UV — BP365 / FT395 / LP397

This is worth acquiring because it substantially expands what you can do with the microscope. The combination is directly documented in the IM35 currently equipped with fluorescence cubes. 

Original Zeiss filter-set numbers

There is a useful numbering correspondence:

Filter Set 01 — DAPI/UV

BP365

FT395

LP397

Filter Set 09 — FITC

BP450–490

FT510

LP515/520 depending on period/version

Filter Set 15 — Rhodamine

BP546

FT580

LP590

Zeiss documentation explicitly identifies FSET 09 as FITC, FSET 15 as Rhodamine and FSET 01 as DAPI. 

There are also later/alternative Zeiss FITC sets such as Set 10, BP450–490 / FT510 / BP515–565. 

One important distinction when buying

I wouldn’t search simply for “Zeiss filter cube 09”.

The glass combination may be correct while the physical cube/module is wrong for an IM35. Zeiss subsequently used several reflector-module designs. Your IM35 needs the older reflector arrangement that physically fits its fluorescence slider/tray.

So the best second-hand searches are things such as:

“Zeiss IM35 fluorescence filter”

“Zeiss IM 35 fluorescence cube”

“Zeiss IM35 reflector”

“Zeiss BP450-490 FT510 LP520”

“Zeiss BP546 FT580 LP590”

“Zeiss BP365 FT395 LP397”

For your purposes, BP450–490 / FT510 / LP520 is the one I’d buy first, because it should be an excellent match for the FDA you’ve already ordered.

I searched current listings specifically for the **older Zeiss IM/IM35 system**, rather than modern Zeiss fluorescence cubes.

The most interesting current lead I found is an eBay listing for a **Zeiss Inverted Microscope Fluorescence Filter Cube, part 45 28 88 (452888), marked “02 Filter #2”**, at about **US$299.99**. citeturn0search15 I would **not buy this yet**, though: I haven’t found enough evidence that 452888 is mechanically compatible with the IM35 tray or that its filter wavelengths are useful for FDA.

More importantly, I’ve now identified an **IM/IM35-specific part number**:

**Zeiss 46 63 01-9901 (466301-9901) — Filter Insert Housing with filters for IM / IM35.**

An eBay listing explicitly identifies this as being for **“IM / IM35”**. Unfortunately that particular example is currently sold out. citeturn0search2 This is an excellent part number to put into saved eBay searches.

I also found the **IM35 Foto 35 filter slider, part 47 17 81**. One sold for only **US$32.99**, described as having clear optics. citeturn0search5 This tells us that IM35-specific optical hardware does turn up separately and sometimes very cheaply.

### What I would look for:

For your FDA work, the ideal find remains an **IM35-compatible filter housing/cube containing:**

**BP 450–490 → FT 510 → LP 520**

There’s particularly strong evidence for this exact combination. A documented IM35 fluorescence outfit has two cubes:

**FITC:** BP450–490 / FT510 / LP520  

**UV:** BP365 / FT395 / LP397. citeturn0search14turn0search8

Even better, a published experiment specifically used **fluorescein diacetate (FDA) with a Zeiss IM35**, using **BP450–490 / FT510 / LP520**. citeturn0search0 So we aren’t merely extrapolating from FITC—the exact combination is documented for **FDA on the IM35**.

### Best eBay searches to save

I’d use these exact search terms:

– `Zeiss IM35 466301`

– `Zeiss IM35 46 63 01`

– `Zeiss IM35 fluorescence filter`

– `Zeiss IM35 filter insert`

– `Zeiss IM35 fluorescence cube`

– `Zeiss IM fluorescence filter`

– `Zeiss BP450-490 FT510 LP520`

At the moment, **I haven’t found a live inexpensive listing that I can confidently tell you to buy**. That’s preferable to accidentally directing you toward one of the much more common later Zeiss cubes that won’t fit.

The good news is that **466301-9901** gives us a much more specific IM35 part number to hunt for.